Why is the first solid from GeometryInstance.GetInstanceGeometry() null or has zero volume/surface area?

[gopinadh7XTGG]

When calling GetInstanceGeometry() on a GeometryInstance, the first retrieved Solid always has a volume or surface area of 0. Does anyone know why this happens?

Revit Version: 22.0.2.392

[jeremy_tammik · Accepted solution]

I do not know why this happens. I assume there is a reason. I do not really care what the reason is. I suggest that you prepare your code to be able to handle that situation, and not to rely on it remaining that way. It may depend on the geometry instance interaction with various constraints in the BIM or with other BIM elements. Ours is not to wonder why...

[gopinadh7XTGG]

I understand your point. Instead of relying on this behavior staying the same, I'll make sure the code is robust enough to handle that situation properly. Thanks for the suggestion.