no-nested-materials

Code	RM.001
Validator
Compatibility
Tags

Summary

Materials must not contain nested materials to avoid unexpected rendering behavior.

Description

This requirement validates that UsdShade.Material prims don’t have child prims that are also materials. Nested materials can cause unexpected rendering behavior and are not supported in many USD-based renderers and simulation environments.

Materials should be organized as direct children of the Looks scope, without any hierarchical nesting of material prims within other material prims.

Why is it required?

• Prevents unexpected rendering behavior when materials contain nested materials

• Ensures compatibility with USD-based renderers and simulation environments

• Follows USD best practices for material organization

• Avoids ambiguity in material binding resolution

Examples

# Invalid: Material with nested material
def Scope "Looks"
{
    def Material "ParentMaterial"
    {
        # Material shaders and properties...
        
        def Material "NestedMaterial"  # Invalid: Nested material
        {
            # This nested material causes issues
        }
    }
}

# Valid: Materials as direct children of Looks
def Scope "Looks"
{
    def Material "Material_01"
    {
        # Material shaders and properties...
    }
    
    def Material "Material_02"
    {
        # Material shaders and properties...
    }
}

How to comply

• Ensure all Material prims are direct children of the Looks scope

• Do not nest Material prims inside other Material prims

• Organize materials in a flat hierarchy under the Looks scope

• Use proper material binding to reference materials from geometry