no MaterialElementId

[skabart1993]

Hi everyone,

I retrieve the MaterialElementId for every face of the element's solid, but I notice that some faces do not have a MaterialElementId assigned. In the attached pictures, you can see RevitLookup for an architectural column. There are faces with and without a MaterialElementId; however, in Revit, all faces appear to be assigned with one material. I would appreciate it if somebody could explain this.

[jeremy_tammik]

Pure conjecture, just for fun:

• Only visible surfaces are assigned a material id, because it makes no sense for invisible surfaces
• Some surfaces are caused by intersections or joins with other elements and are therefore hidden, not visible, covered

[skabart1993]

Thank you for quick reply,

As seen in the picture, there are six faces of the column, all of which are visible and not hidden.

[jeremy_tammik]

Aha. Does the column display as expected? Are all six faces represented correctly? What material do they display? Maybe some of them have a default material assigned by category or some other overriding property, whereas others have a specific material assigned?

[ricaun]

I guess that's how Revit works.

If you create a family with geometry and do not assign any material, ElementId.InvalidElementId or -1 is assigned in the geometry.

And I am pretty sure Revit uses the Material in the Category in the document as a default Material to display to the user.

[nice3point]

This material is contained in a private property that is not officially available, you can see this if you enable Non-public in RevitLookup. Try to check the property value in Solid or other geometric objects as well