material-shader-inputs#

Code	VM.BIND.002
Validator
Compatibility
Tags

Summary#

Shader inputs must have correct types matching their shader specification to ensure proper material behavior and prevent runtime errors.

Description#

All shader inputs must conform to their specification-defined types. This requirement validates that:

MDL Shader Inputs: Input types match the MDL module parameter definitions
Built-in Shader Inputs: Input types match the Shader Definition Registry (SDR) specifications
Float Values: No invalid values (NaN or Infinity) are present

Type mismatches can cause:

Rendering failures or incorrect visual output
Runtime errors in simulation environments
Data corruption when materials are processed
Unpredictable shader behavior

The validator checks both MDL-based shaders (using info:mdl:sourceAsset) and built-in shaders (using info:id) against their respective specifications.

Why is it required?#

Prevents runtime errors from type mismatches
Ensures predictable shader behavior
Maintains data integrity throughout the pipeline
Enables reliable material interchange between tools
Catches authoring errors early in the asset creation process
Prevents invalid numerical values that can break rendering

Examples#

# Invalid: Type mismatch in shader input
def Material "InvalidMaterial"
{
    def Shader "Shader"
    {
        uniform token info:implementationSource = "sourceAsset"
        uniform asset info:mdl:sourceAsset = @./SimPBR.mdl@
        uniform token info:mdl:sourceAsset:subIdentifier = "SimPBR"
        
        # Incorrect: diffuse_texture expects asset type, not string
        string inputs:diffuse_texture = "./textures/albedo.png"
        
        # Incorrect: metallic expects float, not int
        int inputs:metallic = 1
    }
}

# Invalid: NaN or Inf values in float inputs
def Material "InvalidFloatMaterial"
{
    def Shader "Shader"
    {
        uniform token info:implementationSource = "sourceAsset"
        uniform asset info:mdl:sourceAsset = @./SimPBR.mdl@
        uniform token info:mdl:sourceAsset:subIdentifier = "SimPBR"
        
        # Incorrect: Invalid float value
        float inputs:roughness = nan
    }
}

# Valid: Correct types matching specification
def Material "ValidMaterial"
{
    def Shader "Shader"
    {
        uniform token info:implementationSource = "sourceAsset"
        uniform asset info:mdl:sourceAsset = @./SimPBR.mdl@
        uniform token info:mdl:sourceAsset:subIdentifier = "SimPBR"
        
        # Correct: asset type for texture
        asset inputs:diffuse_texture = @./textures/albedo.png@
        
        # Correct: float type for metallic
        float inputs:metallic = 1.0
        
        # Correct: float type for roughness with valid value
        float inputs:roughness = 0.5
    }
}

# Valid: Built-in UsdPreviewSurface shader
def Material "PreviewMaterial"
{
    def Shader "Surface"
    {
        uniform token info:id = "UsdPreviewSurface"
        
        # Correct types according to UsdPreviewSurface spec
        color3f inputs:diffuseColor = (0.8, 0.8, 0.8)
        float inputs:metallic = 0.0
        float inputs:roughness = 0.5
    }
}

How to comply#

For MDL Shaders:#

Verify input types against the MDL module specification
Use the correct USD/Sdf type for each parameter (e.g., asset, float, color3f)
Ensure info:mdl:sourceAsset points to a valid MDL file
Include the info:mdl:sourceAsset:subIdentifier attribute