AlphaBlendSortTest.usda

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Alpha Blend Sort Test

Description

Opacity in UsdPreviewSurface has a number of pitfalls (schema versioning, application of light even when fully transparent, opacityThreshold, etc.).

This asset tests for and showcases some of the various issues that can happen with that. It may not be possible to render this asset as intended with UsdPreviewSurface (clarification needed) since that always applies lighting even to fully transparent parts of surfaces (e.g. light response on fully transparent glass).

Problem: Visible boundaries

Problem: Incorrectly interpreted as masked instead of blended

The model is translucent (opacity is set but not opacityThreshold), yet some apps interpret it as cutoff material.

Problem: Incorrect blending of transparent surfaces

The coplanar shadow planes should not write to depth since they are transparent, and should darken each other.

Problem: ?

Not sure what’s going on here, looks like all surfaces are interpreted as opaque yet rendered partially transparent.

License Information

To the extent possible under law, Felix Herbst / prefrontal cortex has waived all copyright and related or neighboring rights to this asset.

AlphaBlendSortTest.usda

#usda 1.0
(
    customLayerData = {
        string creator = "Three.js USDZExporter"
    }
    defaultPrim = "StageRoot"
    endTimeCode = 100
    framesPerSecond = 60
    metersPerUnit = 1
    startTimeCode = 0
    timeCodesPerSecond = 60
    upAxis = "Y"
)

def Xform "StageRoot"
{
    def Xform "GameObject_19"
    {
        matrix4d xformOp:transform = ( (1, 0, 0, 0), (0, 1, 0, 0), (0, 0, 1, 0), (0, 0, 0, 1) )
        uniform token[] xformOpOrder = ["xformOp:transform"]

        def Xform "Shadows_20"
        {
            matrix4d xformOp:transform = ( (1, 0, 0, 0), (0, 1, 0, 0), (0, 0, 1, 0), (0, 0, 0, 1) )
            uniform token[] xformOpOrder = ["xformOp:transform"]

            def Xform "Shadow1_23" (
                prepend apiSchemas = ["MaterialBindingAPI"]
                prepend references = @./geometries/Geometry_7.usd@</Geometry>
            )
            {
                rel material:binding = </Materials/Material_5>
                matrix4d xformOp:transform = ( (0.7227923689262957, -6.524213866211724e-7, -0.5760579247048901, 0), (0.2046202329458557, 0.000001901808820767934, 0.2567414611888293, 0), (0.000003151849124212561, -1.0191191961221802, 0.000005052769658335941, 0), (-0.595999956, 0, -0.0440000035, 1) )
                uniform token[] xformOpOrder = ["xformOp:transform"]
            }

            def Xform "Shadow2_24" (
                prepend apiSchemas = ["MaterialBindingAPI"]
                prepend references = @./geometries/Geometry_7.usd@</Geometry>
            )
            {
                rel material:binding = </Materials/Material_5>
                matrix4d xformOp:transform = ( (0.9162692, 0, 0, 0), (0, -1.5225203843506833e-8, 0.2861209362252038, 0), (0, -1.0102997337605517, -5.376055171802598e-8, 0), (0.618000031, 0, -0.00100000016, 1) )
                uniform token[] xformOpOrder = ["xformOp:transform"]
            }

            def Xform "Shadow3_22" (
                prepend apiSchemas = ["MaterialBindingAPI"]
                prepend references = @./geometries/Geometry_8.usd@</Geometry>
            )
            {
                rel material:binding = </Materials/Material_6>
                matrix4d xformOp:transform = ( (1.86491, 0, 0, 0), (0, -4.863094950971973e-8, 0.9139012486309495, 0), (0, -1.0103000537605686, -5.3760568746019645e-8, 0), (-0.023999989, -0.00505150063, -0.0009999997, 1) )
                uniform token[] xformOpOrder = ["xformOp:transform"]
            }
        }
    }
}

def "Materials"
{
    def Material "Material_5"
    {
        token inputs:frame:stPrimvarName = "st"
        token outputs:surface.connect = </Materials/Material_5/PreviewSurface.outputs:surface>

        def Shader "PreviewSurface"
        {
            uniform token info:id = "UsdPreviewSurface"
            color3f inputs:diffuseColor.connect = </Materials/Material_5/Texture_6_diffuse.outputs:rgb>
            float inputs:metallic = 0
            float inputs:opacity = 0.50980395
            float inputs:opacity.connect = </Materials/Material_5/Texture_6_diffuse.outputs:a>
            float inputs:roughness = 1
            int inputs:useSpecularWorkflow = 0
            token outputs:surface
        }

        def Shader "uvReader_st"
        {
            uniform token info:id = "UsdPrimvarReader_float2"
            float2 inputs:fallback = (0, 0)
            token inputs:varname.connect = </Materials/Material_5.inputs:frame:stPrimvarName>
            float2 outputs:result
        }

        def Shader "Transform2d_diffuse" (
            sdrMetadata = {
                string role = "math"
            }
        )
        {
            uniform token info:id = "UsdTransform2d"
            float2 inputs:in.connect = </Materials/Material_5/uvReader_st.outputs:result>
            float2 inputs:scale = (1, 1)
            float2 inputs:translation = (0, 0)
            float2 outputs:result
        }

        def Shader "Texture_6_diffuse"
        {
            uniform token info:id = "UsdUVTexture"
            asset inputs:file = @textures/Texture_6_000000_0.509803951.png@
            float4 inputs:scale = (0, 0, 0, 0.50980395)
            float2 inputs:st.connect = </Materials/Material_5/Transform2d_diffuse.outputs:result>
            token inputs:wrapS = "repeat"
            token inputs:wrapT = "repeat"
            float outputs:a
            float outputs:b
            float outputs:g
            float outputs:r
            float3 outputs:rgb
        }
    }

    def Material "Material_6"
    {
        token inputs:frame:stPrimvarName = "st"
        token outputs:surface.connect = </Materials/Material_6/PreviewSurface.outputs:surface>

        def Shader "PreviewSurface"
        {
            uniform token info:id = "UsdPreviewSurface"
            color3f inputs:diffuseColor.connect = </Materials/Material_6/Texture_6_diffuse.outputs:rgb>
            float inputs:metallic = 0
            float inputs:opacity = 0.29803923
            float inputs:opacity.connect = </Materials/Material_6/Texture_6_diffuse.outputs:a>
            float inputs:roughness = 1
            int inputs:useSpecularWorkflow = 0
            token outputs:surface
        }

        def Shader "uvReader_st"
        {
            uniform token info:id = "UsdPrimvarReader_float2"
            float2 inputs:fallback = (0, 0)
            token inputs:varname.connect = </Materials/Material_6.inputs:frame:stPrimvarName>
            float2 outputs:result
        }

        def Shader "Transform2d_diffuse" (
            sdrMetadata = {
                string role = "math"
            }
        )
        {
            uniform token info:id = "UsdTransform2d"
            float2 inputs:in.connect = </Materials/Material_6/uvReader_st.outputs:result>
            float2 inputs:scale = (1, 1)
            float2 inputs:translation = (0, 0)
            float2 outputs:result
        }

        def Shader "Texture_6_diffuse"
        {
            uniform token info:id = "UsdUVTexture"
            asset inputs:file = @textures/Texture_6_000000_0.298039228.png@
            float4 inputs:scale = (0, 0, 0, 0.29803923)
            float2 inputs:st.connect = </Materials/Material_6/Transform2d_diffuse.outputs:result>
            token inputs:wrapS = "repeat"
            token inputs:wrapT = "repeat"
            float outputs:a
            float outputs:b
            float outputs:g
            float outputs:r
            float3 outputs:rgb
        }
    }
}