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Q&A: Error message: Material property cannot be applied to thin sheet body

Question
I imported a CAD file. Now I am trying to apply a Material Property to one of the objects, but I get the following error message:

Material property cannot be applied to a thin sheet body!

Why won’t TracePro allow the property to be applied?

Synopsis
Error message: Material property cannot be applied to thin sheet body

Solution
“To accurately perform the ray trace, TracePro needs to make sure that the geometry in a TracePro model “makes sense” for the ray trace. One part of this is to ensure that Material Properties are applied only to “valid solid objects”.

When an object in TracePro is assigned a Material Property, the TracePro ray trace will use the index of refraction from that property to refract the rays that enter and exit the object. If an object in TracePro were, for example, an infinitely thin sheet (a single planar surface), and a Material Property were applied to that surface, should the ray refract? Is the ray entering the object? or exiting? The error message that you are observing is intended to avoid problems like this.

Another instance that may cause this message is after importing geometry from a CAD program. Let’s say that the CAD program imported a 2x2x2 block with a 1x1x1 block stacked on top of it (sharing a coincident surface). If it imports these as 2 separate objects, that is OK as they are each a valid solid object (and may be made of different materials).

If it imports these as a single object, then to be a valid solid, the coincident surface should no longer appear. Some CAD programs leave such “internal” surfaces in the model, but they can potentially confuse the TracePro ray trace. TracePro makes a decision at the point where a ray intersects a surface. If a Material Property has been assigned to an object, then TracePro must decide if it is entering or exit an object to make the correct decision about how the ray refracts. When it encounters an “internal surface”, it will erroneously behave as if it is exiting the object.

I suggest reviewing the model to see if your object meets 1 of the 2 descriptions above. If it is an imported CAD model, you may find that the CAD program includes some export options, and you can try any option that suggests it is saving the file as solids.

If the suggestions above do not seem to fit your case, it is certainly possible that TracePro is in error. Please contact us and we can troubleshoot the problem and hopefully provide you with a workaround.”

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