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in categories  freecad  opensource  permalink:  37   posted on 15.04.2014 17:41
From Yorik

IFC support in FreeCAD




We have recently reached a very important point with the Architecture module of FreeCAD: Import and export of IFC files. The support to IFC is not fully compliant yet, but I believe it is stable enough so I can talk about it here.

The IFC format is a very important foundation of any decent BIM workflow. It is basically the one and only proper exchange format we have between all the BIM-capable applications out there, such as Revit, AllPlan or ArchiCAD. IFC is an extension of the STEP format, which is very widely used in mechanical engineering, and also an ISO standard. It is also not a closed format, owned by a single company, but open, human-readable, and maintained by a consortium. This only is a tremendous change compared to older 2D formats such as DWG, that are closed, encrypted, undocumented and proprietary. As a result, implementing DWG support is an almost impossible task for an open-source project, while the IFC format is well documented, the documentation is publicly available, and there are many examples available to programmers. There is even a huge guidebook that explains in details how things must be implemented. All this makes IFC support much easier to implement.

If you read BIM blogs on the internet, you will notice that many people speak against IFC. It is hard, however, to not see a direct relation between these negative opinions and Revit. Revit has a very "everything into one model, one application" ideology, and many of its users see IFC as "too dumb", unable to carry the complex relationships and parametric tissue present in a Revit model.

This is certainly true, although with each new version of the IFC format, its authors try to address more of these parametric relationships. But fundamentally, the purpose of IFC is to describe a building, not the software tools you used to design it. This is at the same time a weakness and a strength, in my opinion. And you have nowadays many voices raising against relying on too complex parametric chains and going back to more simple, easily understandable model structures.

This also speaks of another important point of a modern BIM workflow: collaboration. IFC is not meant to be a format for archiects, but a format for the whole construction family, including engineers and constructors. They will use your IFC files in a very different way as you. You might want to keep your complex relationships so you can import your IFC back into your application, and everything connects, but they will do very different things with it. Engineers will use it as a guide, and sometimes rebuild some sections of it, and constructors will want to extract quantities from it, and won't be interested in how you designed it. For them, there is even a side-format called COBIE which presents the contents of an IFC model as a big spreadsheet...

So thinking of your model as "easy to exchange" with others is a very good way to look at the problem in my opinion, and in that scope, IFC is much, much more interesting. If you model objects that are easy to identify (correctly named and placed in a coherent hierarchy) and easy to modify (which often means: delete and redo it from scratch) by others, the limitations of IFC become totally supportable. And the advantages are huge.

Implementation in FreeCAD


The IFC import/export mechanism in FreeCAD relies on one amazing piece of software called IfcOpenShell. IfcOpenShell is a reader/writer for IFC files, built upon OpenCasCade, the same geometry kernel as we use in FreeCAD. The consequence of this is that both applications communicate extremely well, and the import and export of geometry is very reliable and relatively fast already.

IfcOpenShell has been supporting reading of IFC files for quite some time, but in its latest development version, it now also allows writing. This is now supported in FreeCAD too, and if you can compile FreeCAD and IfcOpenShell yourself, in order to benefit from the latest developments of both applications, you already have full IFC import and export. If not you'll need a little of patience, until these come to a proper release.

When importing an IFC file into FreeCAD, IfcOpenShell will get all the entities derived from the IfcProduct class. That involves basically all building elements, such as walls, windows, roofs, etc. and extract their shape. When a corresponding Arch object exists, for example a wall, such object is created, and the shape is attributed. If no corresponding Arch object exists, for example a piece of furniture, a standard Part object is created. This ensures you that all building products present in the IFC file are imported, even if there is no corresponding Arch object.

At the moment, the shape of the object comes already fully computed, with its openings, subtractions, etc. In the future, we'll work together with the IfcOpenShell developers to get more interesting behaviour, such as having the openings as separate parameters, or retrieving the baselines of the walls.

When exporting an IFC file from FreeCAD, there are currently still a couple of limitations: only Arch objects can be exported, and they can contain no curves. Other than that, any shape is correctly exported,and it's thrilling to see your wildest FreeCAD designs faithfully exported to such a "serious" format as IFC! It is best to have alreay a building + floor(s) structure in FreeCAD to export, but if none is there a default one is created for you.

The biggest task that awaits us now is complying to standards. IFC specification is very complex, and there are a lot of little particularities that such or such application will read or not read. So this will require heavy testing, and help from everybody who wants to see this going further. Several members of the FreeCAD community are already doing some heavy testing, don't hesitate to join us!

As a starter, I mounted a little test file in FreeCAD. This file also serves to demonstrate other features of FreeCAD and the Arch workbench, such as extracting 2D views and calculating quantities. Consider it as a "FreeCAD BIM test":



Get the FreeCAD file from here, and the exported IFC file here. There is also a list of exported objects for you to compare with. I'll add it to the FreeCAD example files later.

If you want to help with testing, a first thing you might want to do is try the IFC file in your BIM application, and head to the FreeCAD forum to report your results! IfcOpenShell also has a test file here.

in categories  freecad  opensource  permalink:  27   posted on 14.03.2014 17:57
From Yorik

FreeCAD Architecture tutorial

This is a copy of this original article I wrote on the FreeCAD wiki, about doing BIM modeling with FreeCAD,that I copied it here for archiving purposes. I advise you to read the original article, the quality is much better.

Introduction

Arch tutorial 00.jpg

This tutorial aims at giving you the basics to work with the Arch Workbench. I will try to make it simple enough so you don't need any previous experience with FreeCAD, but having some experience with 3D or BIM applications will be useful. In any case, you should be prepared to look for yourself for further information about how FreeCAD works on the FreeCAD documentation wiki. The Getting started page is a must read, if you have no previous experience with FreeCAD. Also check our tutorials section, and on youtube you will also find a lot more of FreeCAD tutorials.

The purpose of the Arch Workbench is to offer a complete BIM workflow inside FreeCAD. As it is still under development, don't expect to find here the same tools and level of completion as grown-up commercial alternatives such as Revit or ArchiCAD, but on the other hand, FreeCAD being used in a much bigger scope than these applications, the Arch Workbench greatly benefits from the other disciplines FreeCAD caters to, and offers some features rarely seen in traditional BIM applications.

Here are, for example, a couple of interesting features of FreeCAD's Arch Workbench that you'll hardly find in other BIM apps:

  • Architectural objects are always solids. From FreeCAD's strong mechanical background, we learned the importance of always working with solid objects. This ensures a much more error-free workflow, and very reliable boolean operations. Since cutting through 3D objects with a 2D plane, in order to extract sections, is also a boolean operation, you can immediately see the importance of this point.
  • Architectural objects can always have any shape. No restrictions. Walls don't need to be vertical, slabs don't need to look like slab. Any solid object can always become any architectural object. Very complex things, usually hard to define in other BIM applications, like a floor slab curving up and becoming a wall (yes Zaha Hadid, it's you we're talking about), present no particular problem at all in FreeCAD.
  • The whole power of FreeCAD is at your fingertips. You can design architectural objects with any other tool of FreeCAD, such as the PartDesign Workbench, and when they are ready, convert them to architectural objects. They will still retain their full modeling history, and continue totally editable. The Arch Workbench also inherits much of the Draft Workbench functionality, such as snapping and working planes.
  • The Arch Workbench is very mesh-friendly. You can easily design an architectural model in a mesh-based application such as Blender or SketchUp and import it in FreeCAD. If you took care of the quality of your model and its objects are non-manifold solid shapes, turning them into architectural objects only requires the press of a button.

At the time I'm writing this, though, the Arch Workbench, as the rest of FreeCAD, suffers some limitations. Most are being worked on, though, and will disappear in the future.

  • FreeCAD is no 2D application. It is made for 3D. There is a reasonable set of tools for drawing and editing 2D objects with the Draft Workbench and Sketcher Workbench, but it is not made for handling very large (and sometimes badly drawn) 2D CAD files. You can usually successfully import 2D files, but don't expect very high performance if you want to keep working on them in 2D. You have been warned.
  • No materials support. FreeCAD will have a complete Material system, able to define very complex materials, with all the goodies you can expect (custom properties, material families, rendering and visual aspect properties, etc), and the Arch Workbench will of course use it when it is ready.
  • Very preliminary IFC support. You can already import IFC files, quite reliably, provided IfcOpenShell is installed on your system, but exporting is still not officially supported. This is worked on both by the FreeCAD and IfcOpenShell developers, and in the future we can expect full-powered IFC support.
  • Most Arch tools are still in development. That means that automatic "wizard" tools that create complex geometry automatically, such as Arch Roof or Arch Stairs can only produce certain types of objects, and other tools that have presets, such as Arch Structure or Arch Window only have a couple of basic presets. This will of course grow over time.
  • Relations between objects in FreeCAD are still not officially available. These, for example the relation between a window and its host wall, are currently implemented in the Arch Workbench with temporary (and therefore somewhat limited) methods. Many new possibilities will arise when this feature will be fully available.
  • Units are being implemented in FreeCAD, which will allow you to work with any unit you wish (even imperial units, you guys from the USA can be eternally grateful for this to Jrgen, FreeCAD's godfather and dictator). But at the moment the implementation is not complete, and the Arch workbench still doesn't support them. You must consider it "unit-less".


FreeCAD version 0.14 required

This tutorial was written using FreeCAD version 0.14. You will need at least this version number in order to follow it. Earlier versions might not contain all the needed tools,or they could lack options presented here.


Typical workflows

The Arch Workbench is mainly made for two kinds of workflows:

  • Build your model with a faster, mesh-based application such as Blender or SketchUp, and import them in FreeCAD in order to extract plans and section views. FreeCAD being made for precision modeling, at a much higher level than what we usually need in architectural modeling, building your models directly in FreeCAD can be heavy and slow. For this reason, such a workflow has big advantages. I described it in this article on my blog. If you care to model correctly and precisely (clean, solid, non-manifold meshes), this workflow gives you the same performance and precision level as the other.
  • Build your model directly in FreeCAD. That is what I will showcase in this tutorial. We will use mostly three workbenches: Arch, of course, but also Draft, whose tools are all included in Arch, so there is no need to switch workbenches, and Sketcher. Conveniently, you can do as I usually so, which is to create a custom toolbar in your Arch workbench, with Tools -> Customize, and add the tools from the sketcher that you use often. This is my "customized" Arch workbench

Arch tutorial 01.jpg

In this tutorial, we will model the house in 3D, based on the 2D drawings we'll download from the net, and extract from it 2D documents, such as plans, elevations and sections.

Preparation

Instead of creating a project from scratch, Let's take an example project to model, it will save us time. I chose this wonderful house by the famous architect Vilanova Artigas (see a series of pictures by Pedro Kok), because it is close to where I live, it is simple, it's a wonderful example of the amazing modernist architecture of So Paulo (it is even for sale if you have "a few" Reals to spend), and dwg drawings are easily available.

We will use the 2D DWG drawings obtained from the link above (you need to register to download, but it's free) as a base to build our model. So the first thing you'll want to do is to download the file, unzip it, and open the DWG file inside with a dwg application such as DraftSight. Alternatively, you can convert it to DXF with a free autility such as the Teigha File Converter. If you have the Teigha converter installed (and its path set in the Arch preferences settings), FreeCAD is also able to import DWG files directly. But since these files can sometimes being of bad quality and very heavy, it's usually better open it first with a 2D CAD application and do some cleaning.

Here, I removed all the detail drawings, all the titleblocks and page layouts, did a "clean" ("purge" in AutoCAD slang) to remove all unused entities, reorganized the sections at a logical location in relation to the plan view, and moved everything to the (0,0) point. After that, our file can be opened quite efficiently in FreeCAD. Check the different options available in Edit -> Preferences -> Draft -> Import/Export, they can affect how (and how quickly) DXF/DWG files are imported.

This is how the file looks after being opened in FreeCAD. I also changed the thickness of the walls (the contents of the "muros" group), and flipped a couple of doors that were imported with wrong X scale, with the Draft Scale tool:

Arch tutorial 02.jpg

The DXF importer (which also takes care of DWG files, since when importing DWG files, they are simpl converted to DXF first), groups the imported objects by layer. There is no layer in FreeCAD, but there are groups. Groups offer a similar way to organize the objects of your files, but don't have specific properties, like AutoCAD layers, that apply to their contents. But they can be placed inside other groups, which is very handy. The first thing we might want to do here, is to create a new group (in the tree view, right-click on the document icon, add a group, right click on it to rename it as "base 2D plans", and drag and drop all the other objects into it.

Building the walls

Like most Arch objects, walls can be built upon a big variety of other objects: lines, wires (polylines), sketches, faces or solid (or even on nothing at all, in which case they are defined by height, width and length). The resulting geometry of the wall depends on that base geometry, and the properties you fill in, such as width and height. As you might guess, a wall based on a line will use that line as its alignment line, while a wall based on a face will use that face as its base footprint, and a wall based on a solid will simply adopt the shape of that solid. This allows about any shape imaginable to become a wall.

There are different possible strategies to build walls in FreeCAD. One might want to build a complete "floor plan" with the sketcher, and build one, big, wall object from it. This technique works, but you can only give one thickness for all the walls of the project. Or, you can build each piece of wall from separate line segments. Or, this is what we will do here, a mix of both: We will build a couple of wires on top of the imported plan, one for each type of wall:

Arch tutorial 03.jpg

As you see, I've drawn in red the lines that will become concrete walls (a pictures search of the house can help you to see the different wall types), the green ones are the exterior brick walls, and the blue ones will become the inner walls. I passed the lines through the doors, because doors will be inserted in the walls later, and will create their openings automatically. Walls can also be aligned left, right or centrally on their baseline, so it doesn't matter which side you draw the baseline. I also took care on avoiding intersections as much as I could, because our model will be cleaner that way. But we'll take care of intersections later.

When this is done, place all those lines in a new group if you want, select each line one by one, and press the Arch Wall tool to build a wall from each of them. You can also select several lines at once. After doing that, and correcting widths (exterior walls are 25cm wide, inner walls are 15cm wide) and some alignments, we have our walls ready:

Arch tutorial 04.jpg

We could also have built our walls from scratch. If you press the Arch Wall button with no object selected, you will be able to click two points on the screen to draw a wall. But under the hood, the wall tool will actually draw a line and build a wall on it. In this case, I found it more didactic to show you how things work.

Did you notice that I took great care not to cross the walls? this will save us some headache later, for example if we export our work to other applications, that might not like it. I have only one intersection, where I was too lazy to draw two small line segments, and drew one big wire crossing another. This must be fixed. Fortunately, all Arch objects have a great feature: you can add one to another. Doing that will unite their geometries, but they are still editable independently after. To add one of our crossing walls to the other, just select one, CTRL + select the other, and press the Arch Add tool:

Arch tutorial 05.jpg

On the left is are the two intersecting walls, on the right the result after adding one to the other.

An important note about parametric objects

Something is important to consider already. As you can see, in FreeCAD, everything is parametric: Our new "united" wall is made from two walls, each based on a baseline. When you expand them in the tree view, you can see all that chain of dependencies. As you can imagine, this little game can quickly become very complex. Furthermore, if you already know how to work with the sketcher, you might have wanted to draw the baselines with constrained sketches. This whole complexity has a cost: it raises exponentially the number of calculations that FreeCAD has to perform to keep your model geometry up to date. So, think about it, don't add unnecessary complexity when you don't need it. Keep a good balance between simple and complex objects, and keep these for the cases where you really need them.


For example, I could have drawn all my baselines above without caring about what crosses what, and fix things with the Arch Add tool later. But I would have raised much the complexity of my model, for no gain at all. Better make them correct right from the start, and keeping them as very simple pieces of geometry.

Now that our walls are okay, we need to raise their height, until they intersect the roof. Then, since the wall object still cannot be cut automatically by roofs (this will happen some day, though), we will build a "dummy" object, that follows the shape of the roof, to be subtracted from our walls.

First, by looking at our 2D drawings, we can see that the highest point of the roof is 5.6m above the ground. So let's give all our walls a height of 6m, so we make sure they will be cut by our dummy roof volume. Why 6m and not 5.6m? You may ask. Well, if you already worked with boolean operations (additions, subtractions, intersections), you must already know that these operations usually don't like much "face-on-face" situations. They prefer clearly, frankly intersecting objects. So by doing this, we keep on the safe side.

To raise the height of our walls, simply select all of them (don't forget the one we added to the other) in the tree view, and change the value of their "height" property.

Before making our roof and cutting the walls, let's make the remaining objects that will need to be cut: The walls of the above studio, and the columns. The walls of the studio are made the same way as we did, on the superior floor plan, but they will be raised up to level 2.6m. So we will give them the needed height so their top is at 6m too, that is, 3.4m. Once this is done, let's move our walls up by 2.6m: Select them both, put yourself in frontal view (View -> Standard Views -> Front), press the Draft Move button, select a first point, then enter 0, 2.6, 0 as coordinates, and press enter. Your objects now have jumped 2.6m high:

Arch tutorial 06.jpg

About coordinates

The Draft objects, and most Arch objects too, obey to a Draft system called working planes. This system defines a 2D plane where next operations will take place. If you don't specify any, that working plane adapts itself to the current view. This is why we switched to frontal view, and you see that we indicated a movement in X of 0 and in Y of 2.6. We could also have forced the working plane to stay on the ground, by using the Draft SelectPlane tool. Then, we would have entered a movement of X of 0, Y of 0 and Z of 2.6.


Now let's move our walls horizontally, to their correct location. Since we have points to snap to, this is easier: Select both walls, press the Draft Move tool, and move them from one point to the other:

Arch tutorial 07.jpg

Finally, I changed the color of some walls to a brick-like color (so it's easier to differentiate), and made a small correction: Some walls don't go up to the roof, but stop at a height of 2.60m. I corrected the height of those walls.

Raising the structure

Now, since we'll have to cut our walls with a subtraction volume, we might as well see if there aren't other objects that will need to be cut that way. There are, some of the columns. This is a good opportunity to introduce a second arch object: the Arch Structure. Structure objects behave more or less like walls, but they aren't made to follow a baseline. Rather, their prefer to work from a profile, that gets extruded (along a profile line or not). Any flat object can be a profile for a structure, with only one requirement: they must form a closed shape.

For our columns, we will use another strategy than with the walls. Instead of "drawing" on top of the 2D plans, we will directly use objects from it: the circles that represent the columns in the plan view. In theory, we could just select one of them, and press the Arch Structure button. However, if we do that, we produce an "empty" structural object. This is because you can never be too sure at how well objects were drawn in the DWG file, and often they are not closed shapes. So, before turning them into actual columns, let's turn them into faces, by using the Draft Upgrade tool twice on them. The first time to convert them into closed wires (polylines), the second time to convert those wires into faces. That second step is not mandatory, but, if you have a face, you are 100% sure that it is closed (otherwise a face cannot be made).

After we have converted all our columns to faces, we can use the Arch Structure tool on them, and adjust the height (some have 6m, other only 2.25m height):

Arch tutorial 08.jpg

On the image above, you can see two columns that are still as they were in the DWG file, two that were upgraded to faces, and two that were turned into structural objects, and their height set to 6m and 2.25m.

Note that those different Arch objects (walls, structures, and all the others we'll discover) all share a lot of things between them (for example all can be added one to another, like we already saw with walls, and any of them can be converted to another). So it's more a matter of taste, we could have made our columns with the wall tool too, and converted them if needed. In fact, some of our walls are concrete walls, we might want to convert them to structures later.

Subtractions

Now it is time to build our subtraction volume. The easiest way will be to draw its profile on top of the section view. Then, we will rotate it and place it at its correct position. See why I placed the sections and elevations like that before beginning? It will be very handy for drawing stuff there, then moving it to its correct position on the model.

Let's draw a volume, bigger than the roof, that will be subtracted from our walls. To do that, I drew two lines on top of the base of the roof, then extended them a bit further with the Draft Trimex tool. Then, I drew a wire, snapping on these lines, and going well above our 6 meters. I also drew a blue line on the ground level (0.00), that will be or rotation axis.

Arch tutorial 09.jpg

Now is the tricky part: We will use the Draft Rotate tool to rotate our profile 90 degrees up, in the right position to be extruded. To do that, we must first change the working plane to the YZ plane. Once this is done, the rotation will happen in that plane. But if we do like we did a bit earlier, and set our view to side view, it will be hard to see and select our profile, and to know where is the basepoint around which it must rotate, right? Then we must set the working plane manually: Press the Draft SelectPlane button (it is in the "tasks" tab of the tree view), and set it to YZ (which is the "side" plane). Once you set the working plane manually, like that, it won't change depending on your view. You can now rotate your view until you have a good view of all the things you must select. To switch the working plane back to "automatic" mode later, press the Draft SelectPlane button again and set it to "None".

Now the rotation will be easy to do: Select the profile, press the Draft Rotate button, click on a point of the blue line, enter 0 as start angle, and 90 as rotation:

Arch tutorial 10.jpg

Now all we need to do it to move the profile a bit closer to the model (set the working plane to XY if needed), and extrude it. This can be done either with the Part Extrude tool, or Draft Trimex, which also has the special hidden power to extrude faces. Make sure your extrusion is larger than all the walls it will be subtracted from, to avoid face-on-face situations:

Arch tutorial 11.jpg

Now, here comes into action the contrary of the Arch Add tool: Arch Remove. As you might have guessed, it also makes an object a child of another, but its shape is subtracted from the host object, instead of being united. So now things are simple: Select the volume to subtract (I renamed it as "Roof volume to subtract" in the tree view so it is easy to spot), CTRL + select a wall, and press the Arch Remove button. You'll see that, after the subtraction happened, the volume to subtract disappeared from both the 3D view and the tree view. That is because it has been marked as child of the wall, and "swallowed" by that wall. Select the wall, expand it in the tree view, there is our volume.

Now, select the volume in the tree vieew, CTRL + select the next wall, press Arch Remove. Repeat for the next walls until you have everything properly cut:

Arch tutorial 12.jpg

Remember that for both Arch Add and Arch Remove, the order you select the objects is important. The host is always the last one, like in "Remove X from Y" or "Add X to Y"

A note about additions and subtractions

Arch objects that support such additions and subtractions (all of them except the "visual" helper objects such as the axes) keep track of such objects by having two properties, respectively "Additions" and "Subtractions", that contains a list of links to other objects to be subtracted or added. A same object can be in thr lists of several other objects, as it is the case of our subtraction volume here. Each of the fathers will want to swallow it in the tree view, though, so it will usually "live" in the last one. But you can always edit those lists for any object, by double-clicking it in the tree view, which in FreeCAD enters edit mode. Pressing the escape key exits edit mode.


Making the roofs

Now, all we have to do to complete the structure, is to make the roof and the smaller inner slabs. Again, the easiest way is to draw their profiles on top of the section, with the Draft Wire tool. Here I drew 3 profiles on top of each other (I moved them apart in the image below so you see better). The green one will be used for the lateral borders of the roof slab, then the blue one for the side parts, and the red ones for the central part, that sits above the bathroom block:

Arch tutorial 13.jpg

Then, we must repeat the rotation operation above, to rotate the objects in a vertical position, then move them at their correct places, and copy some of them that will need to be extruded twice, with the Draft Move tool, with the ALT key pressed, which creates copies instead of moving the actual object. I also added two more profiles for the side walls of the bathroom opening.

Arch tutorial 14.jpg

When everything is in place, it's just a matter of using the Draft Trimex tool to extrude, then convert them to Arch Structure objects.

Arch tutorial 15.jpg

After that, we can see some problems arising: two of the columns on the right are too short (they should go up to the roof), and there is a gap between the slab and the walls of the studio on the far right (the 2.60 level symbol on the section view was obviously wrong). Thanks to the parametric objects, all this is very easy to solve: For the columns, just change their height to 6m, fish your roof subtraction volume from the tree view, and subtract it to the columns. For the walls, it's even easier: move them a bit down. Since the subtraction volume continues at the same place, the wall geometry will adapt automatically.

Now one last thing must be fixed, there is a small slab in the bathroom, that intersects some walls. Let's fix that by creating a new subtraction volume, and subtract it from those walls. Another feature of the Draft Trimex tool, that we use to extrude stuff, is that it can also extrude one single face of an existing object. This creates a new, separate object, so there is no risk to "harm" the other object. So we can select the base face of the small slab (look at it from beneath the model, you'll see it), then press the Draft Trimex button, and extrude it up to well above the roofs. Then, subtract it from the two inner bathroom walls with the Arch Remove tool:

Arch tutorial 16.jpg

Floors, stairs and chimney

Now, our structure is complete, we just have a couple of smaller objects to do.

The chimney

Let's start with the chimney. Now you already know how it works, right? Draw a couple of closed wires, move them up at their correct height with the Draft Move tool, extrude them with the Draft Trimex tool, turn the bigger one into a structure, and subtract the smaller ones. Notice how the chimney tube wasn't drawn on the plan view, but I found its position by dragging blue lines from the section views.

Arch tutorial 17.jpg

The floors

The floors are not well represented in the base drawings. When looking at the sections, you cannot know where and how thick the floor slabs are. So I will suppose that the walls are sitting on top of foundation blocks, at level 0.00, and that there are floor slabs, also sitting on those blocks, 15cm thick. So the floor slabs don't run under the walls, but around them. We could do that by creating a big rectangular slab then subtracting the walls, but remember, subtraction operations cost us. Better do it in smaller pieces, it will be "cheaper" in terms of calculation, and also if we do it intelligently, room by room, these will also be useful to calculate floor areas later:

Arch tutorial 18.jpg

Once the wires are drawn, just turn them into structures, and give them a height of 0.15:

Arch tutorial 19.jpg

The stairs

Now the stairs. Met the next of the Arch tools, the Arch Stairs. This tool is still in a very early stage of development, at the time I'm writing, so don't expect too much of it. But it is already pretty useful to make simple, straight stairs. One concept is important to know, the stairs tool is thought to build stairs from a flat floor up to a wall. In other words, when viewed from the top, the stairs object occupies exactly the space that it occupies on the plan view, so the last riser is not drawn (but it is of course taken into account when calculating heights).

In this case, I preferred to build the stairs on the section view, because we'll need many measurements that are easier to get from that view. Here, I drew a couple of red guidelines, then two blue lines that will be the base of our two pieces of stairs, and two green closed wires, that will form the missing parts. Now select the first blue line, press the Arch Stairs tool, set the number of steps to 5, the height to 0.875,the width to 1.30, the structure type to "massive" and the structure thickness to 0.12. Repeat for the other piece.

Then, extrude both green wires by 1.30, and rotate and move them to the right position:

Arch tutorial 20.jpg

On the elevation view, draw (then rotate) the border:

Arch tutorial 21.jpg

Then move everything into place:

Arch tutorial 22.jpg

Don't forget also to cut the column that crosses the stairs, because in BIM it's always bad to have intersecting objects. We are building like in the real world, remember, where solid objects cannot intersect. Here, I didn't want to subtract the column directly from the stairs (otherwise the column object would be swallowed by the stairs object in the tree view, and I didn't like that), so I took the face on which the column was built, and extruded it again. This new extrusion was then subtracted from the stairs.

Right! All the hard work is now done, let's go on with the very hard work!

Doors and windows

Arch Windows are pretty complex objects. They are used to make all kinds of "inserted" objects, such as windows or doors. Yes, in FreeCAD, doors are just a special kind of window. In real life too, if you think of it, no? The Arch Window tool can still be a bit hard to use today, but consider this as a tradeoff, as it was built for maximum power. Almost any kind of window your imagination can produce can be done with it. But as the tool will gain more presets, this situation will certainly become better in the future.

The Arch Window object works like this: It is based on a 2D layout (any 2D object, but preferably a sketch, that contains closed wires (polylines). These wires define the different parts of the window: outer frames, inner frames, glass panels, solid panels, etc. The window objects then has a property that stores what to do with each of these wires: extrude it, place it at a certain offset, etc. Finally, a window can be inserted into a host object such as a wall or structure, and it will automatically create a hole in it. That hole will be calculated by extruding the biggest wire found in the 2D layout.

There are two ways to create such objects in FreeCAD: By using a preset, or drawing the window layout from scratch. We'll look at both methods here. But remember that the preset method does nothing else than creating the layout object and defining the necessary extrusions for you.

Using presets

When pressing the Arch Window tool with no object selected, you are invited either to pick a 2D layout, or to use one of the presets. Let's use the "Simple Door" preset to place the main entrance door of our model. Give it a width of 1m, a height of 2.45m, a W1 size of 0.15m, and leave the other parameters to 0.05m. Then click the lower left corner of the wall, and your new door is created:

Arch tutorial 23.jpg

You will notice that your new door won't appear in the tree view. That is because, by snapping to a wall, we indicated that wall as its host object. Consequently, it has been "swallowed" by the wall. But a right click on it -> Go to selection will find it in the tree.

In this case, as our window is not inserted in any wall (the opening was there already), we might as well detach our window from its host wall. This is done by double-clicking the host wall in the tree view to enter its edit mode. There, you will see the window in its "Subtractions" group. Simply select the window there, press the "remove element" button, then "OK". Our window has now been removed from its host wall, and lies at the bottom of the tree view.

We have a second door, exactly the same as this one, a bit on the left. Instead of creating a new door from scratch, we have two ways to make a copy of the previous one: By using the Draft Move tool, with the ALT key pressed, which, as you already know, copies an object instead of moving it. Or, even better, we can use the Draft Clone tool. The clone tool produces a "clone" of a selected object, that you can move around, but that retains the shape of the original object. If the original object changes, the clone changes too.

So all we need to do now is select the door, press the Draft Clone tool, then move the clone to its correct position with the Draft Move tool.

Organizing your model

Arch tutorial 24.jpg

Now would be a good time to do a bit of housecleaning. Since we already have two windows, it is a good moment to do some cleaning in the tree view: Create a new group, rename it to "windows", and drop the 2 windows in it. I also recommend you to separate other elements that way, such as the walls and structures. Since you can also create groups inside groups, you can organize further, for example by placing all elements that form the roof into a separate group, so it is easy to turn on and off (turning a group visible or invisible does the same with all objects inside).

The Arch Workbench has some additional tools to organize your model: the Arch Site, Arch Building and Arch Floor. Those 3 objects are based on the standard FreeCAD group, so they behave exactly like groups, but they have a couple of additional properties. For example, floors have the ability to set and manage the height of the contained walls and structure, and when they are moved, all their contents are moved too.

But here, since we have only one building with only one (and a half) floor, there is no real need to use such objects, so let's stick with simple groups.

Now, let's get back to work. Turn off the roof group, so we can see better inside, and switch the Display Mode of the floor objects to Wireframe (or use the Draft ToggleDisplayMode tool) so we can still snap to them, but we can see the plan view underneath. But you can also turn off the floors completely, then place your doors at level 0, then raise them of 15cm with the Draft Move tool.

Let's place the interior doors. Use the "Simple Door" preset again, make doors of 1.00m and 0.70m wide x 2.10m high, with W1 size of 0.1m. Make sure you snap to the correct wall when you place them, so they automatically create a hole in that wall. If it is hard to place them correctly, you can place them at an easier location (at the corner of the wall, for example, then move them. The "hole" will move together.

If by mistake you hosted a window in the wrong wall, it is easy to fix: Remove the window from the "Subtraction" group of the host wall in edit mode, as we saw above, then add it to the "Subtraction" group of the correct wall, by the same method, or, simply, using the Arch Remove tool.

A little work later, all our doors are there:

Arch tutorial 25.jpg

After a closer look at the elevation view, I now detected another error: The top of the brick walls is not as 2.60m, but 17.5cm lower, that is, 2.425m. Fortunately, windows based on presets have a facility: You can alter their general dimensions (width and height) from their properties. So let's change their height to 2.425 - 0.15, that is, 2.275. The second window, as it is a clone of the first one, will adapt too. This is basically where the true magic of parametric design appears.

Now we can look at the really interesting stuff: How to design your own custom windows.

Creating custom windows

As I explained above, Arch Window objects are created from 2D layouts, made of closed elements (wires (polylines), circles, rectangles, anything). Since Draft objects cannot hold more than one of these elements, the preferred tool to draw window layouts is the Sketcher. Unfortunately, with the sketcher, it is not possible to snap to external objects like with the Draft workbench, which would be useful here, since our elevations are drawn already. Fortunately, a tool exists to convert Draft objects to a sketch: The Draft To Sketch tool.

So, let's start by building our first window layout. I drew it on the elevation, using several rectangles: One for the outer line, and 4 for the inner lines. I stopped before the door, because, remember, our door already has a frame there:

Arch tutorial 26.jpg

Then, select all the rectangles, and press the Draft To Sketch button (and delete the rectangles, because this tool doesn't delete the original objects, in case something goes wrong). Then, with the new sketch selected, press the Arch Window tool:

Arch tutorial 27.jpg

The tool will detect that the layout has one outer wire and several inner wires, and automatically proposes you a default configuration: One frame, made by subtracting the inner wires from the outer one, extruded by 1m. Let's change that, by entering the window's edit mode, by double-clicking on it in the tree view:

You will see a "Default" component, that has been created automatically by the Window tool, that uses the 5 wires (always subtracting the other ones from the biggest one), and has an extrusion value of 1. Let's change its extrusion value to 0.1, to match what we used in the doors.

Then, let's add 4 new glass panels, each using a single wire, and give them an extrusion of 0.01, and an offset of 0.05, so they are placed at the middle of the frame. This will be how your window looks like when you are finished:

Arch tutorial 28.jpg

I suppose now you must have understood the power of this system: Any combination of frames and panels of any shape is possible. If you can draw it in 2D, it can exist as a full valid 3D object.

Now, let's draw the other pieces, then we'll move everything into place together. But first. we'll need to do some corrections to the base 2D drawing, because some lines are clearly missing, where the windows meet the stairs. We can fix that by offsetting the stairs line by 2.5cm with the Draft Offset tool (with ALT pressed of course, to copy our lines instead of moving them). Now we can draw our layout, with wires, then convert them to a sketch, then making a window of it.

After doing that a couple of times (I made it in 4 separate pieces, but it's up to you to decide), we have our facade complete:

Arch tutorial 29.jpg

Now, as before, it's just a matter of rotating the pieces, and moving them to their correct position:

Arch tutorial 30.jpg

Last missing piece, there is a segment of wall that didn't appear on the plan view, that we need to add. We have several options for that, I chose to draw a line on the ground plane, then move it up to the correct height, then create a wall from it. Then, we also need to fish up our roof subtraction volume (it must have stayed in the last column), then subtract it. Now this side of the building is ready:

Arch tutorial 31.jpg

Ready? Not quite. Look at the image above, we did our doors with a 5cm frame, remember (it was the default from the preset). But the other windows have 2.5cm frames. This needs to be fixed.

Editing windows

We already saw how to build and update window components, via the window's edit mode, but we can also edit the underlying sketch. Preset windows are not different than custom windows, the Arch Window tool only created the underlying sketch fo you. Select our door object (the original, not the copy, remember, we made a clone), and expand it in the tree view. There is our sketch. Double-click it to enter edit mode.

the Sketcher Workbench is an extremely powerful tool. It doesn't have some of the Draft conveniences, such as snapping or working planes, but it has many other advantages. In FreeCAD you will frequently use one or another depending on the need. The most important feature of the sketcher is constraints. Constraints allow you to automatically fix the position of some elements relative to others. For example, you can force a segment to always be vertical, or to always be at a certain distance to another.

When we edit our door sketch, we can see that it is made on a fully constrained sketch:

Arch tutorial 32.jpg

Now all we need to do is edit the 5cm distances between the outer line and the inner line, by double-clicking them, and changing their value to 2.5cm (Remember, the units are still not fully functional at the time I'm writing this). After clicking the "OK" button, our door (and its clone) have been updated.

Working without 2D support

Until now our work has been relatively easy, because we had the underlying 2D drawings to base our work upon. But now, we must do the opposite facade and the glass atrium, and things are getting more complicated: The opposite facade drawing has a lot of wrong things, doesn't represent the atrium at all, and we have simply no drawing for the inner walls of the atrium. So we will need to invent a couple of things ourselves. Be sure to have a look at reference pictures to figure out how things are made. Or do it as you wish!

One thing we can already do: duplicate the complicated stairs window with the Draft Move tool, because it is equal on both sides:

Arch tutorial 33.jpg

Note that here, I preferred to duplicate with the Draft Move tool instead of using a clone, because the clone currently doesn't support different colors inside objects. The difference is that the clone is a copy of the final shape of the original object, while if you copy an object, you create a new object and give it all the same properties as the original one (therefore, also its base sketch and its window components definition, which are both stored as properties).

Now we must attack the parts that are not drawn anywhere. Let's start with the glass wall between the sitting room and the atrium. It'll be easier to draw it on the elevation view, because we'll get the correct height of the roof. Once you are in plan view, you can rotate the view from the menu View -> Standard Views -> Rotate left or right, until you get a comfortable view to work, like this:

Arch tutorial 34.jpg

Note how on the image above, I made a line from the model to the left section, to get the exact width of the window. Then, I reproduced that width on the elevation view and divided it into 4 pieces. Then I built one main window piece, plus 4 additional windows for the sliding doors. The sketcher sometimes has difficulties with overlapping wires, that's why I preferred to keep them separated like this:

Arch tutorial 35.jpg

After the necessary rotations, everything clicks perfectly into place:

Arch tutorial 36.jpg

We still need some corner piece there. A little useful trick with the Draft SelectPlane tool, if you have a face selected when you press the button, the working plane matches this face (at least its position, and if the face is rectangular, it also tries to match its axes). This is useful to draw 2D objects directly on the model, such as here, we can draw a rectangle to be extruded directly at its correct position:

Arch tutorial 37.jpg

Then let's do the two remaining pieces. One is easy, it is a copy of what's on the other side, so we can simply use the 2D drawing:

Arch tutorial 38.jpg

The other one is a bit tricky, by looking at the pictures, we see that it has many vertical divisions, like the stairs windows. By chance (or very good design from Vilanova Artigas), the width of our window, of 4.50m, is exactly the same as the stairs window, so we can use the exact same division: 15 pieces of 30cm. Here I used the Draft Array tool to copy over the two lines 15 times,and drew rectangles on top of them:

Arch tutorial 39.jpg

Once this is done, we can create our window with the same method we already know. Another small useful trick, in case you haven't found it yourself already: When editing a window, if you change the name of a component, it actually creates a duplicate of it. So to create the 15 inner glass panels, instead of clicking 15 times the "add" button and fill 15 times the data, you can just keep editing one, and change its name and wire, it will create a copy each time.

After the window is rotated and moved into place, the atrium is complete:

Arch tutorial 40.jpg

Edits and fixes

Now when we look at our back elevation, and compare it with the plan, we see that there are some differences that need to be fixed. Namely, the bedroom windows are smaller than I first thought, and we'll need to add some more walls. In order to do that properly, some floors need to be cut:

Arch tutorial 41.jpg

We have of course several ways to do that, making a subtraction volume would be an easy way, but it would add unnecessary complexity to the model. Better to edit the base wire of each floors. This is where the Draft Edit mode comes into action. By expanding these floors in the tree view, then making their base wire visible, we can then double-click them to enter edit mode. There, we can move their points, or add or remove points. With this,editing our floor plates becomes easy.

Arch tutorial 42.jpg

After some more sweat (the person who made those drawings obviously became pretty lazy when did this last elevation, much is drawn wrong), we finally have our complete house:

Arch tutorial 43.jpg

Note the chimney tube, which is made from a circle I used to make a hole in the chimney block, that I extruded, then converted into a tube with the Part Offset tool.

Problems in objects

Sometimes an object you made can have problems. For example, the object it was based onto has been deleted, and the object can therefore not recalculate its shape. These are usually shown to you by a little red sign on their icon, and/or a warning in the output window. There is no generic recipe to fix these problems, because they can have many origins. But, the easiest way to solve them is often to delete them, and, if you didn't delete their base objects, recreate them.


Output

Now, after all the hard work we passed through to build this model, comes the reward: What can we do with it? Basically, this is the big advantage of working with BIM, all our traditional architectural needs, such as 2d drawings (plans, sections, etc), renderings, and calculations (bills of quantities, etc) can all be extracted from the model. And, even better, regenerated every time the model changes. I'll show you here how to obtain these different documents.

Preparations

Before starting to export stuff, one consideration is interesting to do: As you saw, our model is becoming increasingly complex, with a lot of relationships between objects. This can make subsequent calculation operations, such as cutting through the model, heavy. One quick way to magically "simplify" drastically your model, is to remove all of this complexity, by exporting it to the STEP format. That format will preserve all your geometry, but will discard all the relationships and parametric constructions, keeping only the final shape. When reimporting that STEP file into FreeCAD, you will get a model that has no relationship, and a much smaller file size. Think of it as an "output" file, that you can regenerate anytime from your "master" file:

Arch tutorial 44.jpg

Exporting to IFC and other applications

Arch tutorial 45.jpg

One of the very fundamental things you need when working with BIM is to be able to import and export IFC files. This is still a work in progress in FreeCAD. IFC format is already supported, and importing IFC files into FreeCAD is already pretty reliable. Exporting is still experimental, though, and has currently many limitations. However, things are bettering and we should get proper IFC export very soon.

IFC export requires very little setup, once the necessary software libraries are installed. You only need to recreate the building structure, which is needed in all IFC files, by adding an Arch Building to your file, then an Arch Floor, then moving all the groups of objects that compose your model in it. Make sure you leave your construction geometry (all the 2D stuff we've been drawing) out of it to avoid making your IFC file unnecessarily heavy.

Another thing to set, is to check the "Role" property of structural elements. Since IFC has no "generic" structural element, like FreeCAD, we need to assign them roles (column, beam, etc...) so the exporter knows what element to create in the IFC file.

In this case, we need our whole architectural system, so the IFC exporter can know if an object must be exported as a wall or a column, so we are using our "master" model, not our "output" model.

Once this is done, simply select your building object, and choose the "Industry Foundation Classes" format. Exporting to non-BIM applications, such as Sketchup is also easy, you have several export formats at your disposal, such as Collada, STEP, IGES ou OBJ.

Rendering

FreeCAD also features a rendering module, the Raytracing Workbench. That workbench currently supports two render engines, PovRay and LuxRender. Since FreeCAD is not designed for image rendering, the features that the Raytracing workbench offer to you are somewhat limited. The best course of action when you want to do proper rendering, is to export your model to a mesh-based format such as OBJ or STL, and open it in an application more suited to rendering, such as blender. The image below has been rendered with blender's cycles engine:

Arch tutorial 47.jpg

But, for a quick rendering, the Raytracing workbench can already do a good job, with the advantage of being very easy to setup, thanks to its templates system. This is a rendering of our model fully made within FreeCAD, with the Luxrender engine, using the "indoor" template.

Arch tutorial 48.jpg

The Raytracing workbench still offers you very limited control over materials, but lighting and environments are defined in templates, so they can be fully customized.

2D drawings

Certainly the most important use of BIM is to produce 2D drawings automatically. This is done in FreeCAD with the Arch SectionPlane tool. This tool allows you to place a section plane object in the 3D view, that you can orient to produce plans, sections and elevations. Section planes must know what objects they must consider, so once you have created one, you must add objects to it with the Arch Add tool. You can add individual objects, or, more conveniently, a group, a floor or a whole building. This allows you to easily change the scope of a certain section plane later, by adding or removing objects to/from that group. Any change to these objects gets reflected in the views produced by the section plane.

The section plane automatically produces cut views of the objects it intersects. In other words, to produce views instead of sections, you just need to place the section plane outside of your objects.

Arch tutorial 49.jpg

The section planes can produce two different outputs: shape objects, that live in the same document as your 3D model, or drawing views, that are made to use on a drawing sheet produced by the Drawing workbench. Each of these behave differently, and has its own advantages.

Shape views

This output is produced by using the Draft Shape2DView tool with a section plane selected. You produce a 2D view of the model directly in the 3D space, like on the image above. The main advantage here is that you can work on them using the Draft tools (or any other standard tool of FreeCAD), so you can add texts, dimensions, symbols, etc:

Arch tutorial 50.jpg

On the image above, two Shape2D views have been produced for each section, one showing everything, the other showing only the cut lines. This allows us to give it a different line weight, and turn hatching on. Then, dimensions, texts and symbols have been added, and a couple of DXF blocks have been imported to represent the furniture. These views are then easy to export to DXF or DWG, and open in your favorite 2D CAD application, such as LibreCAD or DraftSight, where you can work further on them:

Arch tutorial 51.jpg

Note that some features are still not supported by the DXF/DWG exporter so the result in your 2D application might differ a bit. For example, in the image above, I had to redo the hatching, and correct the position of some dimension texts. If you place your objects in different groups in FreeCAD, these become layers in your 2D CAD application.

Drawing views

The other kind of output that can be produced from section planes is a Drawing view. These are produced by using the Draft Drawing tool with a section plane selected. This method has one big limitation compared to the previous one: you have limited possibilities to edit the results, and at the moment, things like dimensioning or hatching are still not natively supported.

On the other hand, the final output being easier to manipulate, and the graphical possibilities of the SVG format being huge, in the future, undoubtedly this will be the preferred method. At the moment, though, you'll get better results using the previous one.

Arch tutorial 52.jpg

On the image above, the geometry is the direct output of the section plane, but some other Draft objects have been added, such as dimensions and hatched polygons, and another view object with same scale and offset values has been produced from them with the Draft Drawing tool. In the future, such operations will be done directly on the Drawing page, leaving your model totally clean.

Quantities extraction

This is another very important task to be performed on BIM models. In FreeCAD, things look good right from the start, since the OpenCasCade kernel of FreeCAD already takes care of calculating lengths, areas and volumes for all the shapes it produces. Since all Arch objects are solids, you are always guaranteed to be able to obtain a volume from them.

Using spreadsheets

There is a brand-new workbench in FreeCAD, the Spreadsheet Workbench, that is the perfect tool for collecting such information about our model. It can count objects of a certain name or a certain type, or display a specific properties of those objects. The spreadsheet workbench features two objects: The spreadsheet object is a simple spreadsheet container, that you can edit, and place values inside the cells, but has no automation. The cell controller, on the other hand, is an object that you must insert in a spreadsheet, that controls a series of cells of its host spreadsheet, filling them according to what you specify. This, provided that you organized your model well, allows you to easily retrieve individual values:

Arch tutorial 53.jpg

Note that the spreadsheet workbench is still very new, and like everything very new, still contains many bugs and limitations. But for simple summaries like this, it already works well. The resulting spreadsheet can then be exported to a CSV file, which can be imported in any spreadsheet application.

The survey mode

Another way to survey your model and extract values, is to use the Arch Survey mode. In this mode, you can click on points, edges, faces or double-click to select whole objects, and you get altitude, length, area or volume values, shown on the model, printed on the FreeCAD output window, and copied to the clipboard, so you can easily pick and paste values in another opened application

Arch tutorial 54.jpg

Conclusion

I hope this gives you a good overview of the available tools, be sure to refer to the Arch Workbench and Draft Workbench documentation for more (there are more tools that I didn't mention here), and, more generally, to the rest of the FreeCAD documentation. Pay a visit to the forum too, many problems can usually be solved there in no time, and follow my blog for news about he Arch workbench development.

The file created during this tutorial can be found here


in categories  freecad  opensource  permalink:  24   posted on 11.02.2014 19:26
From Yorik

Quantity survey in FreeCAD



Today a friend quantity surveyor gave me this idea, that resulted in this quickly made but, I think, fast and useful tool, now available from the Arch workbench:



The idea is simple: you press the tool, then you pick edges, faces or whole objects (by double-clicking them). Each time, a label is added, a line is printed in the output window, and the numeric value is copied to the clipboard, so you can paste it in a spreadsheet. The quantity registered is a length, an area or a volume, depending on what you selected. The value is rounded according to the Draft dimension precision preference.

To finish, double-click on no object or click the toolbar button again. All the labels are then removed.

This does the job that other tools do (info macros, etc...) but I wanted something really fast and simple and adapted for quantity surveying, so you can easily select graphically the measurements you need, and keep your spreadsheet open and quickly fill the values.

Enjoy!

in categories  freecad  opensource  permalink:  20   posted on 07.02.2014 14:10
From Yorik

IFC browser in FreeCAD





A little addition for FreeCAD, is this IFC browser (Find it under the Arch->Utilities menu). It simply allows you to read the contents of an IFC file in an easier way than a text editor. This is above all useful for testing purposes, when you want to chack if some object was imported or exported correctly...

The code doesn't rely on FreeCAD, so it can easily be turned into an external application.

in categories  freecad  opensource  permalink:  19   posted on 06.02.2014 19:01
From Yorik

FreeCAD Parts library





There is a little side-project to FreeCAD, which aims at collecting reusable objects under a creative commons license, that we are currently hosting at https://github.com/yorikvanhavre/FreeCAD-library . It features a small browser integrated into FreeCAD, but can also be used with other applications, since all objects are also stored as STEP files.

It currently doesn't contain a lot of objects, but it grows slowly. If you wish to contribute with some objects, look at the readme file on the repository above for instructions.

Enjoy!