3D concept sketching with greasepencil and IFC

edited July 30 in General

I like to sketch. I never learned 3D sketching myself, but I did a lot of 2D sketching when I worked in an architecture firm. One issue I've always noticed is how BIM programs are generally not friendly to the early concept / design phase when it comes to artistic experimentation. We tended to use a lot of other 3D programs for concepts, and 2D sketching, and would later have to re-model in BIM programs.

Wouldn't it be nice, if, say, we could sketch in 3D and use it in BIM software, and even assign them semantic metadata, so that from early concept to late stage - the BIM components are seamless? But more importantly, the design intent has less potential to be lost as the design changes hands from the designers to the drafters in larger firms?

Say, for example, this little piece of fusion urban design:

... another shot ...

Original license:


Animated grease pencil demo file.
Blender 2.82 Splash Screen 

Credits: Andry Rasoahaingo - License CC-BY-SA 3.0

So, greasepencil + IFC? Let's do it! And, let's take the IFC and bring it into Revit (I have selected an IfcStair as an example)!

... another angle, with more prominent greasepencil ...

Let's take it a step further and start cutting sections and annotating:

... and one more section for kicks:

The greasepencil to IFC conversion still has some quirks, and Im sure I've broken a lot of geometrical topological rules in the process, but as you can see some of it certainly comes through nicely. A starting point, I guess.

See for yourself - the attached grease1.ifc is only 7.1mb :)



  • Oh Boy! @Moult you're moving so fast! ;o)

  • ah, you turned the sketch lines into circular rebar ;)

  • edited July 30

    I've wondered about Grease Pencil as well, but more from the perspective of design documentation. The fact that GP already has different line styles and layers built in means you can set line weights, layers and other such details needed for annotation. Also with the new possibility in Blender 2.9 of converting 3d objects to Grease Pencil objects, that seems to suggest a pathway for extracting line drawing elevations from Blender models. I don't know if an SVG export of the Grease Pencil objects would give worthwhile results, but this is probably worth experimenting on.

    Apart from freehand sketching in 3d like you've expressed, if @stephen_l 's CAD transform tools and the Construction Line tools in Blender can work very well with Grease Pencil objects, (good enough that Grease Pencil already allows you to constrain your line to an axis so you can draw straight lines) it means you can actually work back and forth between 3d and 2d sketches and then either trace over those sketches with Archipack or convert 3d elements from the sketches into Archipack objects to take advantage of Archipack's parametric features where needed.

    One more advantage Grease Pencil brings is that for presentation drawings, you can go to town creating stylized environments (and annotations) for your 3d models with all sorts of possibilities. Clearly beyond software development, there is a need to see more experimentation with architectural workflows using Blender and tutorial videos such as @dimitar's out there.

    One more thing I'm thinking about which is not necessarily related to IFC (or maybe it is) is design coordination right inside Blender. There is a multi-user add-on for Blender (Repo here: https://gitlab.com/slumber/multi-user) which already takes care of the asynchronous link between remote Blender instances. It would be interesting stress testing this with copious use of the annotate tool for design coordination, maybe on the open design project and seeing how fast design coordination at early stage of design / concept development can happen using grease pencil and other tools, and how effective that process can be (or not!).

  • edited July 31

    @brunopostle it is worthwhile mentioning that IFC does support 3D polylines... but a lot of BIM software will not properly import it. Therefore I had to resort to converting greasepencil strokes into IfcSweptDiskSolid, which so happens to be also what is commonly used for rebar :)

    @DADA_universe greasepencil definitely needs to be explored further. Also, thanks for the link about the multi-user add-on, I didn't realise that was possible! I must find some buddies to test it out with! And perhaps add to the wiki directory?

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