What controls the color of objects in a IFC?

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hanslammerts
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What controls the color of objects in a IFC?

Postby hanslammerts » Sun Sep 02, 2018 8:29 pm

Hi there,

I want to drop this question about the right handling of colors here.

As a last statement of one member here..
"The IFC standard is very ambiguous when it comes to colors. The color of objects can come from many places in the IFC hierarchy."
It sounds like a recipe trouble in BIM.

https://www.linkedin.com/groups/3690870 ... 8039061504
cadgiru
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Re: What controls the color of objects in a IFC?

Postby cadgiru » Mon Sep 03, 2018 5:15 am

hanslammerts wrote:
Sun Sep 02, 2018 8:29 pm
Hi there,

I want to drop this question about the right handling of colors here.

As a last statement of one member here..
"The IFC standard is very ambiguous when it comes to colors. The color of objects can come from many places in the IFC hierarchy."
It sounds like a recipe trouble in BIM.

https://www.linkedin.com/groups/3690870 ... 8039061504
The easy answer for FC, You get the color of the exported object (at least when using ifcOpenShell). For a more elaborate answer, please explain reason for question.

regards
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yorik
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Re: What controls the color of objects in a IFC?

Postby yorik » Mon Sep 03, 2018 2:22 pm

Basically IFC objects get their color from an IfcSurfaceStyle entity that you attach to them. This is independent from material color or anything, and acts as a kind of "override", so you can have a concrete wall that appears yellow in the BIM app. That's the idea behind it I guess...

Indeed in FreeCAD we map the object color (Shape Color property) to an IfcSurfaceStyle when exporting, and map related IfcSurfaceStyle to Shape Color property on import... A further refinement I haven't looked at yet is to support objects that have more than one color (per-face color), and transparency.
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hanslammerts
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Re: What controls the color of objects in a IFC?

Postby hanslammerts » Sat Oct 26, 2019 12:18 pm

It would be great if colors of rebar ifc objects stay rigid for ALL ifc capable software. In fact, it is a must if you want to leave drawings at your desk. How is going to be tackled?
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bernd
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Re: What controls the color of objects in a IFC?

Postby bernd » Sat Oct 26, 2019 2:49 pm

AFAI an object could have two colors, one which is assigned to the shape and the other is assigned to the material which is assigned to the shape. I have seen various ifc of various CAD which have different collors for the shape and the material. Usually the CAD apps uses the shape color.

Furthermore some ifc viewer namely BIMCollab does display under certain circumstances some objects just grey regardless of the color. This quit often happens in BIMCollabZoom with rebars.

Is there a special reason why is the color that important for you? For me it is important because we use different colors for different concrete types.
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bernd
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Re: What controls the color of objects in a IFC?

Postby bernd » Sat Oct 26, 2019 6:55 pm

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hanslammerts
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Re: What controls the color of objects in a IFC?

Postby hanslammerts » Sat Oct 26, 2019 7:51 pm

Yes there are good reason to have rigid colors. Because they can have meaning. Lets say i'm electrician am I'm looking at some model of a installation. Wouldn't it be neccessary to have electrical wires red, brown, blue have fixed states? If we want 3d models to be used in concrete construction it needs fixed and standardized colors for diameters. Otherwise it can't be interpreted by workers on tablets

At the moment there is little to NO control over Colors which in my opinion is bad. I don't think FreeCAD can solve it all but i would like to have more grip and tools to tweak colors.
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bernd
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Re: What controls the color of objects in a IFC?

Postby bernd » Sun Oct 27, 2019 6:07 pm

if debug is on FreeCAD prints a log if material color of a object is different from shapes color of the object. I now of no other CAD or viewer which gives you this information.

I am in contact with nemetschek allplan dev management to convince them to fix different color bug. ATM I know how to get rid of it inside Allplan. This means at least for the models we create the colors are consistent. If I would like to be sure I import the model in FreeCAD and check the logs ...

Have you ever be involved in placing rebars on site without drawings, just with tablet?
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yorik
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Re: What controls the color of objects in a IFC?

Postby yorik » Mon Oct 28, 2019 6:05 pm

On the FreeCAD side itself, we do have good color control. If you give specific colors to a set of bars in FreeCAD, export them to IFC, all will stay consistent (unless I'm deeply mistaken or FreeCAD deeply bugged :D ). Same if you import an IFC file with colored rebars. So strictly inside FreeCAD, you can round-trip your IFC files without problems.

The problem is, as Bernd says, how other BIM apps treat IFC colors. Some, for ex, have no way to give colors to objects without invoking a material. Then, anything can happen...
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Re: What controls the color of objects in a IFC?

Postby bernd » Wed Oct 30, 2019 1:34 pm

@Yorik: +1

In FreeCAD we do know where the color comes from, and which color we are going to write on which position in IFC. But we do not know about other CAD on import or export.