BBIM|Ifcslab issue

J by juanf on 27 May 2024, edited 28 May 2024 #

Good evening!. Absolutely new here, sorry if breaking any rules...

I'm starting from scratch a new project using BlenderBIM (4.1.1. and 0.0.20240402 version respectively) and experiencing a weird issue with Ifcslab. It seems a bug, maybe I'm doing something wrong as well.

After saving the ifc file and closing the project, when I open it again and load the project any slab becomes a 11 sqm piece again (it was defined as a 912 sqm slab).

Any idea about what can be going wrong?. Thanks in advance.

Best regards,

juanf

T by theoryshaw on 27 May 2024 # +2 votes

Welcome. Are you using the following to change your slab dimensions? If so, don't. :)

Instead, use the 'tab' key, while the slab is selected, to change the footprint of the slab.

J by juanf on 27 May 2024 #

Yes, I was... Thanks a lot, theoryshaw! (though it would be nice to know why, just to understand...) It seems I'm going to experience a deeper learning curve than I guessed from the beginning... ;)

M by Moult on 28 May 2024 # +4 votes

Blender is a general modeling platform with lots of capabilities specific to Blender and to the CG, VFX, animation, and rendering industry.

In contrast, IFC is the ISO standard of how BIM data digitally describes our built environment.

Blender therefore has a lot of features that IFC doesn't, and vice versa - IFC has a lot of features that Blender doesn't. The BlenderBIM Add-on brings the capabilities of IFC to Blender, but being an add-on, there are still plenty of built-in Blender features that are incompatible with IFC.

One of those features is object-level scaling. In IFC, the rule is that objects should be drawn at 1:1 scale (... weeelllll, technically, but let's not get bogged down with the details now). That dialog you were playing with stretches and scales the slab. IFC disallows it, so it resets the scale.

Where possible, we try to "override" Blender behaviour with IFC compatible behaviour, such as if you hit tab to toggle edit mode, it's a special IFC compatible edit mode (remember, IFC geometry is not mesh!). Unfortunately there are many thing we cannot yet override, but hopefully over time it'll get better and better.

S by steverugi on 28 May 2024, edited 28 May 2024 # +1 votes

hi @juanf

Yes, I was... Thanks a lot, theoryshaw! (though it would be nice to know why, just to understand...) It seems I'm going to experience a deeper learning curve than I guessed from the beginning... ;)

If I may, my very simple understanding of this is that IFC sees a slab mostly as an extruded closed line, the green thing when you tab it to enter into edit mode to reveal its vertices and edges. (Theoryshaw's video)

The same polyline is then stretched out, up along the Z axis, to make it solid (I think it's called swept solid or something), so once the info of the vertices and the thickness are known the solid can be visualized in the 3D view somehow.

To do so (give desired thickness to your slab) you need to

select the slab
go to Geometry and Materials > Materials
edit IfcMaterialLayerSetUsage

and edit again the material set item (look for the pencils)

to set the slab thickness using

do not forget to save it on your way out

If you think this procedure is counter-intuitive your are not alone

All of the above is extremely rough and only covers prismatic (constant thickness) solids but it helped me through the IFC jargon

If you do not edit that green line the way it likes it basically IFC ignores what you are doing with it, because it doesn't see it, sort of.

J by juanf on 28 May 2024 #

Dears @Moult and @steverugi .

Thanks again for your kidness... It's a great pleassure to (try to) keep learning with the community and your special support behind. I'll do my best! I have a lot of questions that I'll try to understand step by step (for instance, why the same issue is different for ifcwalls, etc) In fact, I think I'm going to check the blenderbim for begginers serie from Ifcarchitect (Can't remember his name now, sorry!) and the one from 101 or so...

J by juanf on 28 May 2024 #

*KINDNESS, I'm sorry, LOL!

S by steverugi on 28 May 2024, edited 28 May 2024 # +2 votes

@juanf said:

Dears @Moult and @steverugi .

Thanks again for your kidness... It's a great pleassure to (try to) keep learning with the community and your special support behind. I'll do my best! I have a lot of questions that I'll try to understand step by step (for instance, why the same issue is different for ifcwalls, etc) In fact, I think I'm going to check the blenderbim for begginers serie from Ifcarchitect (Can't remember his name now, sorry!) and the one from 101 or so...

yes, I forgot to mention that setting thickness, for instance, in walls and coverings (and other classes) follows the same principle as slabs

they all work in "layers" so you either have a single one or multiple layers to suit your needs

like a wall may have blocks and plaster, a flooring (IfcCovering) tiles, adhesive.. you got the point I guess

that's why the double editing, the first is the layer set, the second the individual layer

cheers and happy modeling

J by juanf on 28 May 2024 # +1 votes

Hi, @steverugi !

I guess I've got it... The idea is that slabs are more kind of a fat plane than a mesh, if you let me put it that way... (And same for walls and so on). I've checked it again meanwhile, and actually I've realized my mistake... Sometimes I was editing from ITEM or wherever I thought (wrong!) when the idea is that any edition must be done in TOOL, since blender and blenderbim are close but not that much, wright?. Grazie mille! ;)

M by Massimo on 28 May 2024 # +1 votes

@theoryshaw how have you managed to see the length of the edges as showed in your video?

T by theoryshaw on 28 May 2024, edited 28 May 2024 # +4 votes

@Massimo said:

@theoryshaw how have you managed to see the length of the edges as showed in your video?

come questo: