Material colors from IfcMaterialDefinitionRepresentation not resolved in geometry color output

[andreabanci87]

Description

When loading IFC files that define material colors through IfcMaterialDefinitionRepresentation
(e.g., via IfcRelAssociatesMaterial → IfcMaterialLayerSetUsage → IfcMaterial → IfcMaterialDefinitionRepresentation → IfcStyledRepresentation → IfcSurfaceStyle → IfcColourRgb),
the PlacedGeometry.color returned by web-ifc uses only the direct geometry-level IfcStyledItem
color, ignoring the material definition chain.

This causes elements like walls to appear gray/white instead of their intended material color.

Reproduction

IFC file: Duplex_A_20110907.ifc
(also known as Ifc2x3_Duplex_Architecture.ifc)

Affected elements: IfcWallStandardCase (e.g., #3797)

Material chain:

• Wall #3797 → IfcRelAssociatesMaterial → IfcMaterialLayerSetUsage #3983
• Layer set #3982 → IfcMaterialLayer → IfcMaterial "Masonry - Brick" #3876
• IfcMaterialDefinitionRepresentation #3891 → IfcStyledRepresentation
• IfcSurfaceStyle "Masonry - Brick" → IfcColourRgb (0.667, 0.392, 0.412) = pink/brick

Direct geometry style:

• Wall shape representation → IfcStyledItem #3794 → IfcSurfaceStyle "Default Wall"
• IfcColourRgb (0.502, 0.502, 0.502) = gray

Expected behavior: Material definition color (pink brick) should take priority or be
merged with the geometry-level style.

Actual behavior: Only the geometry-level "Default Wall" gray color is returned in
PlacedGeometry.color.

Environment

• web-ifc: 0.0.75
• @thatopen/components: 3.3.1
• @thatopen/fragments: 3.3.3

Notes

This appears to be a regression from web-ifc ~0.0.71 where the material definition
representation colors were correctly resolved. Elements with colors defined directly on
geometry representations (e.g., doors, windows) render correctly in both versions.

[beachtom]

So this is tricky one. There is a colour defined on the material ( the reddish colour) and one defined on the wall itself (grey). The IFC standard seems to imply that those defined on the element itself is what should be done - and we changed to adopt that because we had models where that was desired. It seems other viewers adopt the material colour as a priority . The wall does actually define the grey colour (with a specular modify that we don't support yet) as the colour of the wall.

Do you have any suggestions for a good approach here. The IFC spec that I read seems to suggest that what we are doing is correct.

[TrabacchinLuigi]

i think this should be hierarchical material overridden by instance color