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Example files demonstrating wavelength-dependent material and light properties: - spectral-material.usda: Materials with wavelength:reflectance and wavelength:ior (red, glass, fused silica with Sellmeier, foliage, gold) - spectral-light.usda: Light sources with wavelength:emission (D65, D50, A, F2 illuminant presets, custom LED, sodium lamp) - spectral-scene.usda: Complete scene with diamond dispersion, water, copper under D65/D50 lighting 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
232 lines
8.1 KiB
Plaintext
232 lines
8.1 KiB
Plaintext
#usda 1.0
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(
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doc = """LTE SpectralAPI Material Examples
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Demonstrates wavelength-dependent material properties using the wavelength: namespace.
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See doc/lte_spectral_api.md for specification.
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Examples include:
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- Spectral reflectance (wavelength:reflectance)
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- Spectral IOR with various interpolation methods
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- Sellmeier coefficients for glass dispersion
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"""
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metersPerUnit = 1
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upAxis = "Y"
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customLayerData = {
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string unitForWavelength = "nanometers"
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}
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)
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def Scope "Materials"
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{
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# Basic spectral material with reflectance data
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def Material "SpectralRedMaterial"
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{
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token outputs:surface.connect = </Materials/SpectralRedMaterial/PBRShader.outputs:surface>
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def Shader "PBRShader"
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{
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uniform token info:id = "UsdPreviewSurface"
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color3f inputs:diffuseColor = (0.8, 0.1, 0.1)
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float inputs:roughness = 0.4
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float inputs:metallic = 0.0
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float inputs:ior = 1.5
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token outputs:surface
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# LTE SpectralAPI: Spectral reflectance
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# Red-shifted reflectance curve
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float2[] wavelength:reflectance = [
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(380, 0.05), (400, 0.05), (420, 0.05), (440, 0.05),
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(460, 0.06), (480, 0.07), (500, 0.08), (520, 0.10),
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(540, 0.15), (560, 0.25), (580, 0.45), (600, 0.65),
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(620, 0.78), (640, 0.85), (660, 0.88), (680, 0.90),
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(700, 0.91), (720, 0.92), (740, 0.92), (760, 0.93), (780, 0.93)
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] (
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customData = {
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string interpolation = "linear"
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}
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)
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}
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}
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# Spectral material with IOR dispersion (crown glass)
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def Material "SpectralGlassMaterial"
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{
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token outputs:surface.connect = </Materials/SpectralGlassMaterial/PBRShader.outputs:surface>
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def Shader "PBRShader"
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{
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uniform token info:id = "UsdPreviewSurface"
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color3f inputs:diffuseColor = (1.0, 1.0, 1.0)
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float inputs:roughness = 0.0
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float inputs:metallic = 0.0
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float inputs:opacity = 0.1
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float inputs:ior = 1.52
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token outputs:surface
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# LTE SpectralAPI: Spectral IOR (BK7 Crown Glass)
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# IOR varies with wavelength (dispersion)
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float2[] wavelength:ior = [
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(380, 1.5308), (400, 1.5253), (420, 1.5214),
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(440, 1.5183), (460, 1.5158), (480, 1.5137),
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(500, 1.5120), (520, 1.5105), (540, 1.5092),
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(560, 1.5080), (580, 1.5070), (600, 1.5061),
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(620, 1.5053), (640, 1.5046), (660, 1.5039),
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(680, 1.5033), (700, 1.5028), (720, 1.5023),
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(740, 1.5018), (760, 1.5014), (780, 1.5010)
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] (
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customData = {
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string interpolation = "linear"
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}
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)
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}
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}
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# Spectral material with Sellmeier IOR (fused silica)
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def Material "SpectralFusedSilicaMaterial"
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{
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token outputs:surface.connect = </Materials/SpectralFusedSilicaMaterial/PBRShader.outputs:surface>
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def Shader "PBRShader"
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{
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uniform token info:id = "UsdPreviewSurface"
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color3f inputs:diffuseColor = (1.0, 1.0, 1.0)
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float inputs:roughness = 0.0
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float inputs:metallic = 0.0
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float inputs:opacity = 0.05
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float inputs:ior = 1.458
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token outputs:surface
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# LTE SpectralAPI: Sellmeier coefficients for fused silica
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# n^2 = 1 + B1*l^2/(l^2-C1) + B2*l^2/(l^2-C2) + B3*l^2/(l^2-C3)
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# where l is wavelength in micrometers
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float2[] wavelength:ior = [
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(0.6961663, 0.0684043), # (B1, C1) - C1 in um^2
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(0.4079426, 0.1162414), # (B2, C2)
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(0.8974794, 9.896161) # (B3, C3)
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] (
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customData = {
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string interpolation = "sellmeier"
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string unitForWavelength = "micrometers"
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}
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)
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}
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}
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# Spectral material with green foliage reflectance
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def Material "SpectralFoliageMaterial"
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{
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token outputs:surface.connect = </Materials/SpectralFoliageMaterial/PBRShader.outputs:surface>
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def Shader "PBRShader"
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{
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uniform token info:id = "UsdPreviewSurface"
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color3f inputs:diffuseColor = (0.2, 0.5, 0.15)
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float inputs:roughness = 0.6
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float inputs:metallic = 0.0
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token outputs:surface
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# LTE SpectralAPI: Typical green foliage reflectance
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# Shows chlorophyll absorption (low blue/red, high green/NIR)
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float2[] wavelength:reflectance = [
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(380, 0.03), (400, 0.04), (420, 0.04), (440, 0.05),
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(460, 0.05), (480, 0.06), (500, 0.08), (520, 0.12),
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(540, 0.18), (560, 0.20), (580, 0.15), (600, 0.10),
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(620, 0.08), (640, 0.07), (660, 0.06), (680, 0.08),
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(700, 0.35), (720, 0.45), (740, 0.48), (760, 0.50), (780, 0.52)
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] (
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customData = {
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string interpolation = "linear"
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}
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)
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}
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}
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# Gold metal with spectral reflectance
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def Material "SpectralGoldMaterial"
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{
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token outputs:surface.connect = </Materials/SpectralGoldMaterial/PBRShader.outputs:surface>
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def Shader "PBRShader"
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{
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uniform token info:id = "UsdPreviewSurface"
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color3f inputs:diffuseColor = (1.0, 0.84, 0.0)
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float inputs:roughness = 0.2
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float inputs:metallic = 1.0
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token outputs:surface
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# LTE SpectralAPI: Gold reflectance spectrum
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# High reflectance in red/IR, absorption in blue/green
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float2[] wavelength:reflectance = [
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(380, 0.35), (400, 0.38), (420, 0.38), (440, 0.37),
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(460, 0.36), (480, 0.36), (500, 0.42), (520, 0.62),
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(540, 0.82), (560, 0.90), (580, 0.93), (600, 0.95),
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(620, 0.96), (640, 0.97), (660, 0.97), (680, 0.98),
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(700, 0.98), (720, 0.98), (740, 0.99), (760, 0.99), (780, 0.99)
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] (
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customData = {
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string interpolation = "linear"
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}
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)
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}
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}
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}
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def Xform "Geometry"
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{
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# Sphere with red spectral material
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def Sphere "RedSphere"
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{
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double radius = 0.5
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double3 xformOp:translate = (-2, 0.5, 0)
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uniform token[] xformOpOrder = ["xformOp:translate"]
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rel material:binding = </Materials/SpectralRedMaterial>
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}
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# Sphere with glass material (IOR dispersion)
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def Sphere "GlassSphere"
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{
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double radius = 0.5
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double3 xformOp:translate = (-1, 0.5, 0)
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uniform token[] xformOpOrder = ["xformOp:translate"]
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rel material:binding = </Materials/SpectralGlassMaterial>
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}
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# Sphere with fused silica (Sellmeier)
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def Sphere "SilicaSphere"
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{
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double radius = 0.5
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double3 xformOp:translate = (0, 0.5, 0)
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uniform token[] xformOpOrder = ["xformOp:translate"]
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rel material:binding = </Materials/SpectralFusedSilicaMaterial>
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}
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# Sphere with foliage material
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def Sphere "FoliageSphere"
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{
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double radius = 0.5
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double3 xformOp:translate = (1, 0.5, 0)
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uniform token[] xformOpOrder = ["xformOp:translate"]
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rel material:binding = </Materials/SpectralFoliageMaterial>
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}
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# Sphere with gold material
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def Sphere "GoldSphere"
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{
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double radius = 0.5
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double3 xformOp:translate = (2, 0.5, 0)
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uniform token[] xformOpOrder = ["xformOp:translate"]
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rel material:binding = </Materials/SpectralGoldMaterial>
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}
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# Ground plane
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def Mesh "Ground"
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{
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int[] faceVertexCounts = [4]
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int[] faceVertexIndices = [0, 1, 2, 3]
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point3f[] points = [(-5, 0, -5), (5, 0, -5), (5, 0, 5), (-5, 0, 5)]
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normal3f[] primvars:normals = [(0, 1, 0), (0, 1, 0), (0, 1, 0), (0, 1, 0)] (
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interpolation = "vertex"
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)
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}
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}
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