Arch tutorial/de

Einleitung
Dieses Tutorial zeigt Ihnen die Grundlagen für das Arbeiten mit dem Arbeitsbereich Arch. Ich werde versuchen alles so einfach zu beschreiben, sodass keine Vorkenntnisse in FreeCAD notwendig sind. Vorliegende Erfahrungen mit 3D oder Gebäudedatenmodellierung sind jedoch von Vorteil. Unabhängig davon sollten Sie bei Bedarf weitere Informationen über FreeCAD im dazugehörigen Wiki nachschlagen. Besonders wichtig ist die Seite Erste Schritte, die sich FreeCAD-Anfänger unbedingt durchlesen sollten. Weiterhin empfehlenswert sind die Tutorials und die dazu passenden Videos auf Youtube.

Der Zweck des Arbeitsbereichs Arch ist es, alle notwendigen Arbeitsschritte für die Gebäudedatenmodellierung in FreeCAD zusammenzufassen. Da die Software momentan noch in der Entwicklungsphase ist, ist das Angebot an Werkzeugen im Vergleich zu kommerziellen Alternativen wie Revit oder ArchiCAD kleiner. Andererseits ist FreeCAD für einen größeren Aufgabenbereich als diese Programme nutzbar, was beim Arbeiten mit dem Arbeitsbereich Arch einige nützliche Möglichkeiten mit sich bringt, die klassische BIM-Programme nur selten bieten können.

Im Folgenden sind einige Merkmale des Arbeitsbereichs Arch gelistet, die nur selten in anderen BIM-Programmen zu finden sind:


 * Architekturobjekte sind stets Festkörper. Dies ist in Hinsicht des streng technischen Hintergrundes von FreeCAD sehr wichtig. Bool'sche Operationen werden wesentlich fehlerfreier ausgeführt. Dies ist auch in Bezug auf Schnitterstellung ein wichtiger Punkt, da 3D-Objekte durch 2D-Flächen geschnitten werden.


 * Architektonische Objekte können grundsätzlich jede beliebige Form haben. Wände müssen nicht vertikal sein und Decken müssen nicht wie welche aussehen. Jeder beliebige Volumenkörper kann ein architektonisches Objekt sein. Sehr komplexe Dinge, die in anderen BIM Programmen normalerweise nur schwer zu beschreiben sind, z.B. eine Bodenplatte, die sich nach oben krümmt und in die Wand übergeht, stellen in FreeCAD kein besonderes Problem dar.


 * Ihnen stehen die gesamten Möglichkeiten von FreeCAD zur Verfügung. Sie können ihre Objekte in jedem Arbeitsbereich von FreeCAD erstellen (z.B. PartDesign) und hinterher in Architekturobjekte konvertieren. Das Objekt behält dabei seine Modellierungsgeschichte und seine Eigenschaften können nach wie vor geändert werden. Der Arbeitsbereich Arch erbt zudem viele Funktionalitäten des Arbeitsbereichs Draft, wie z.B. Draft Snap oder Ebene markieren.


 * Der Arbeitsbereich Arch unterstützt auch Modelle aus Polygonnetzen. Sie können das gewünschte Modell in einer 3D-Grafiksoftware, die mit Polygonnetzen arbeitet (z.B. Blender oder SketchUp), erstellen und hinterher in FreeCAD importieren. Wenn das Modell sorgfältig erstellt wurde und keine Überschneidungen von 3D-Körpern aufweist, dann ist nur ein Klick notwendig, um daraus ein Architekturobjekt zu erzeugen.

Zum momentanen Zeitpunkt, zu dem ich das Tutorial schreibe, besitzen FreeCAD und auch der Bereich Arch einige Einschränkungen. An den meisten davon wird gearbeitet und sie werden wohl in der Zukunft verschwinden.


 * FreeCAD ist keine 2D-Anwendung, sondern wurde für 3D gemacht. Es gibt zwar in den Arbeitsbereichen Draft und Sketcher eine vernünftige Menge an Werkzeugen für das Zeichnen und Bearbeiten von zweidimensionalen Objekten, doch das Programm wurde nicht für die Verarbeitung von sehr großen (und manchmal schlecht gezeichneten) zweidimensionalen CAD-Dateien ausgelegt. Im Normalfall können solche Dateien zwar mit FreeCAD geöffnet werden, aber man sollte dabei besser keine hohe Leistungsfähigkeit des Programms erwarten. Sie wurden gewarnt.


 * Momentan keine Unterstützung von Materialien. FreeCAD wird irgendwann ein vollständiges System von Materialien bekommen, das die Definition von komplexen Materialien mit all ihren Eigenschaften erlaubt. Der Arbeitsbereich Arch wird diese natürlich auch verwenden können, wenn es soweit ist.


 * Nur eingeschränkte Unterstützung des offenen Standards IFC. Die dazugehörigen IFC-Dateien lassen sich zwar schon importieren, wenn IfcOpenShell auf dem PC installiert ist, aber das Exportieren wird momentan offiziell noch nicht unterstützt. Die Entwickler von FreeCAD und IfcOpenShell arbeiten gemeinsam daran, sodass eine vollständige Unterstützung in der Zukunft zu erwarten ist.


 * Die meisten Werkzeuge im Arbeitsbereich Arch sind noch in Entwicklung. Deshalb können viele der Werkzeuge zum automatischen Generieren von komplexen Strukturen, wie z.B. Arch Roof oder Arch Stairs, bislang nur bestimmte Objekte erzeugen. Andere Werkzeuge mit Voreinstellungen, z.B. Arch Structure oder Arch Window, bieten bisher nur wenige Voreinstellungen zur Auswahl. Der Umfang dieser Werkzeuge wird mit der Zeit sicherlich noch wachsen.


 * Verknüpfungen zwischen Objekten in FreeCAD sind immer noch nicht offiziell verfügbar. Ein Beispiel dafür ist die Verknüpfung zwischen einem Fenster und der dazugehörigen Wand. Diese Verknüpfungen sind momentan nur mir temporären (und somit eingeschränkten) Methoden in FreeCAD implementiert. Es werden sich viele neue Möglichkeiten ergeben, wenn dieses Programmmerkmal irgendwann vollständig verfügbar ist.


 * Einheiten werden noch in FreeCAD implementiert, was die Arbeit mit jeder beliebigen Einheit ermöglichen wird. Momentan ist die Implementierung jedoch noch nicht abgeschlossen und der Arbeitsbereich Arch unterstützt sie noch nicht. Die Arbeits geschieht also einheitenlos.

Typische Vorgehensweise
Die Arch Workbench ist hauptsächlich für zwei Vorgehensweisen ausgelegt:


 * Erstellen Sie das Modell mit einem schnelleren, auf Polygonnetzen basierendem Programm (z.B. Blender oder SketchUp) und importieren Sie das Modell anschließend in FreeCAD, um Pläne zu extrahieren und Schnittansichten zu erstellen. FreeCAD wurde für eine hochpräzise Modellierung ausgelegt, wie sie im Architekturbereich nur selten notwendig ist, sodass die Modellierung von Architekturobjekten unter Umständen langsam und schwerlich verläuft. Aus diesem Grund hat eine Vormodellierung mit 3D-Grafiksoftware mitunter große Vorteile. Ich habe dies in diesem Artikel in meinem Blog beschrieben. Wenn Sie wirklich präzise modellieren wollen (sauber, Volumenkörper, ohne Überschneidungen der Polygonnetze), dann wird Ihnen diese Vorgehensweise dieselbe Präzision und Geschwindigkeit bringen wie die andere.


 * Erstellen des Modells direkt in FreeCAD. Diese Vorgehensweise wird in diesem Tutorial vorgestellt. Dabei benutzen wir hauptsächlich die drei Arbeitsbereiche Arch, Sketcher und Draft. Die Werkzeuge von Draft sind bereits in Arch integriert, sodass kein Wechsel des Arbeitsbereichs notwendig ist. Es ist in diesem Fall zweckdienlich, eine eigene Werkzeugleiste im Arbeitsbereich Arch zu erstellen (Menü: Werkzeuge → Benutzdefiniert) und die häufiger verwendeten Werkzeuge des Arbeitsbereichs Sketcher hinzuzufügen. Meine benutzerdefinierte Werkzeugleiste sieht wie folgt aus:



In diesem Tutorial werden wir ein Haus dreidimensional modellieren, basierend auf zweidimensionalen Zeichnungen, die wir aus dem Internet herunterladen.

Vorbereitung
Um Zeit zu sparen, werden wir das Projekt nicht von Grund auf neu erstellen, sondern ein bereits existierendes Beispielprojekt verwenden. Ich habe dafür das wundervolle Haus des berühmten Architekten Vilanova Artigas ausgewählt, weil ich in der Nähe davon lebe und weil es ein wunderbares Beispiel für die erstaunliche modernistische Architektur Sãu Paolos ist. Die dazugehörigen .dwg-Dateien sind in gepackter Form frei verfügbar (erfordert kostenlose Registrierung). Alternativ kann eine dxf-Version davon hier heruntergeladen werden.

Wir werden die 2D-Zeichnungen in der oben verlinkten dwg-Datei als Basis für unser Modell nutzen. Nach dem Entpacken der Datei sollte die resultierende dwg-Datei mit einer passenden Software wie z.B. DraftSight geöffnet werden. Alternativ kann die Datei auch mit der Software Teigha File Converter in eine dxf-Datei umgewandelt werden. Wenn der Converter installiert ist und sein Pfad in den Einstellungen von Arch richtig konfiguriert ist, dann lassen sich mit FreeCAD dwg-Dateien auch direkt importieren. In der Regel ist es jedoch besser, die Dateien zuerst mit einer 2D-CAD-Software zu öffnen und von unnötigen Details zu bereinigen.

Hier habe ich alle Detailzeichnungen, Überschriften und Seitenlayouts entfernt, habe ungenutzte Instanzen beseitigt, die Abschnitte passend zur realen Lage neu angeordnet und alles zum Nullpunkt (0,0) verschoben. Danach kann die Datei ziemlich schnell von FreeCAD geöffnet werden. Prüfen Sie die verschiedenen Optionen in Bearbeiten → Einstellungen → Import/Export → DXF/DWG, denn diese beeinflussen wie und wie schnell FreeCAD solche Dateien importiert.

So sah die Datei nach dem anschließenden Öffnen in FreeCAD aus. Ich habe zudem die Dicke der Wände der Gruppe "muros" geändert und einige der Türen mit dem Werkzeug Scale umgedreht, weil diese mit der falschen X-Skalierung importiert wurden.



Die Importfunktion für dxf-Dateien, die auch beim Importieren von dwg-Dateien zur Anwendung kommt, gruppiert die importierten Objekte nach Ebenen. Es gibt zwar keine Ebenen in FreeCAD, aber es gibt Gruppen. Gruppen bieten eine ähnliche Form der Organisation von Objekten, haben jedoch keine spezifischen Eigenschaften, die auf alle enthaltenen Objekte angewandt werden (wie bei Ebenen in AutoCAD). Gruppen lassen sich jedoch innerhalb anderer Gruppen platzieren, was sehr hilfreich sein kann. Was wir nun als Erstes tun möchten, ist das Erstellen einer neuen Gruppe im Modellbaum, indem wir per Rechtsklick das Dokument "artigas" anklicken und dann auf Gruppe erstellen klicken. Die neue Gruppe sollte in "base 2D plans" umbenannt werden und alle anderen Gruppen im Modellbaum sollte in diese Gruppe hinein verschoben werden.

Einfügen der Wände
Ebenso wie die meisten anderen Objekte in Arch, können auch Wände mit Hilfe vieler anderer Objekte erstellt werden: Linien, Polylinien, Skizzen, Oberflächen oder Volumenkörper (oder auch von Grund auf, d.h. durch Angabe von Höhe, Breite und Länge). Die resultierende Geometrie der Wand hängt von der Geometrie der eben genannten Hilfsobjekte und ihren Attributen (z.B. der Breite) ab. Wie Sie sich wohl denken können, wird eine Wand, die auf einer Linie basiert, diese Linie für die Ausrichtung nutzen, während eine Wand, die auf einer Oberfläche basiert, diese Oberfläche als Grundfläche verwendet. Bei Volumenkörpern als Hilfsmittel nimmt die Wand die Gestalt des Volumenkörpers an. Folglich können Wände jede beliebige Form annehmen.

Es gibt in FreeCAD mehrere mögliche Strategien zum Konstruieren von Wänden. Eine davon ist es, alle vorgesehenen Wände zunächst mit dem Werkzeug Sketcher zu zeichnen und dann ein einzelnes, großes Wandobjekt daraus zu erstellen. Dies funktioniert zwar, hat aber den Nachteil, dass alle Wände dieselbe Wandstärke (Dicke) haben werden. Alternativ kann jede Wand einzeln skizziert und umgewandelt werden. Am besten ist jedoch ein Mittelweg: Für jede Art von Wand eine Polylinie zeichnen und in ein Wandobjekt umwandeln. Diesen Weg werden wir im Folgenden nehmen.



Wie Sie in der Abbildung sehen können, habe ich Betonwände rot (Vergleichsbilder), die äußeren Ziegelwände grün und die Innenwände blau gezeichnet. Die Wände schneiden dabei die Türen, weil diese erst im Nachhinein eingefügt werden. Wände können außerdem auch links- oder rechtsbündig oder mittig auf ihrer Basislinie platziert werden, sodass es nicht wichtig ist, auf welcher Seite man die Basislinie zeichnet. Ich habe mich außerdem bemüht, Überschneidungen der Linien bestmöglich zu vermeiden, weil unser Modell damit sauberer werden wird. Wir werden uns später nochmal mit Überschneidungen beschäftigen.

Wenn dies erledigt ist, sollten alle erstellten Linien in einer Gruppe abgelegt werden. Anschließend sollten alle Linien gleichen Typs bei gedrückter Strg-Taste ausgewählt werden und das Werkzeug Wand verwendet werden. Hinterher müssen noch die Wandstärken korrigiert werden (Außenwände: 25 cm, Innenwände: 15 cm) und einige Ausrichtungen korrigiert werden. Das Ergebnis sollte wie folgt aussehen:



Wir hätten unsere Wände auch von Grund auf erstellen können. Wenn Sie den Wand-Button ohne gewähltes Objekt drücken, können Sie auf dem Bildschirm zwei Punkte anklicken, um eine Wand zu zeichnen. Unter der Haube allerdings wird das Wand-Werkzeug eine Linie zeichnen und eine Wand darauf bauen. In diesem Fall fand ich es didaktischer, Ihnen zu zeigen, wie die Dinge arbeiten.

Haben Sie bemerkt, dass ich großen Wert darauf gelegt habe, dass sich die Wände nicht kreuzen? Dies wird uns später einige Kopfschmerzen ersparen, wenn wir zum Beispiel unsere Arbeit an andere Anwendungen exportieren, die so etwas nicht mögen. Ich habe nur einen Schnittpunkt, wo ich zu faul war, zwei kleine Liniensegmente zu zeichnen und stattdessen eine große Polygonzugkreuzung gezeichnet habe. Das muss korrigiert werden. Glücklicherweise haben alle Arch-Objekte eine großartige Eigenschaft: Sie können eins mit einem anderen verbinden. Dabei werden ihre Geometrien miteinander vereint, sie sind aber immer noch unabhängig voneinander änderbar. Um eine der kreuzenden Wände mit der anderen zu verbinden, wählen Sie einfach eine, dann die andere bei gedrückter -Taste und wählen das Komponente hinzufügen-Werkzeug:



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

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.

Beim Blick auf unsere 2D-Zeichnungen sehen wir, dass der höchste Punkt des Daches 5,60 m über dem Boden ist. Deshalb werden wir unseren Wänden eine Höhe von 6 m geben, um sicherzustellen, dass sie von unserem Dummy-Dach-Objekt abgeschnitten werden. "Warum 6 m und nicht 5,60 m?" werden Sie vielleicht fragen. Wenn Sie bereits mit Boole'schen Operationen (Vereinigung, Differenz, Schnittmenge) gearbeitet haben, dann wissen Sie, dass diese Operationen "Face-to-Face"-Situationen nicht besonders mögen. Sie ziehen klar und eindeutig kreuzende Objekte vor. Mit dem Längenüberschuss erreichen wir das.

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:



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:



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):



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.



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:



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:



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:



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"

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:



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.



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.



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:



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.



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:



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



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:



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



Then move everything into place:



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:



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


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:



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:



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:



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:



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:



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



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:



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:



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:



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:



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:



After the necessary rotations, everything clicks perfectly into place:



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:



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:



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:



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:



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:



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.



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:



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.

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:



Exporting to IFC and other applications


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:



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.



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.



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:



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:



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.



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:



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



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