Diffuse Transmission

glTF extension: KHR_materials_diffuse_transmission
glTF properties: diffuseTransmissionFactor · diffuseTransmissionTexture · diffuseTransmissionColorFactor · diffuseTransmissionColorTexture

Diffuse transmission models scattered light passing through a surface (e.g. wax, skin, frosted glass), distinct from the specular/refractive transmission in KHR_materials_transmission. Requires KHR_materials_diffuse_transmission to be enabled in the export options.

Shader	Weight attribute	Color attribute	Notes
standardSurface, aiStandardSurface	transmission	transmissionColor
openPBRSurface	transmissionWeight	transmissionColor	Different weight attribute name
StingrayPBS	not supported	not supported	-

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Transmission weight

Factor only

Set the weight attribute directly on the shader.

• standardSurface, aiStandardSurface: set transmission.
• openPBRSurface: set transmissionWeight.

Exports as diffuseTransmissionFactor.

standardSurfaceaiStandardSurfaceopenPBRSurface

standardSurface factor-only diffuse transmission setup.

aiStandardSurface factor-only diffuse transmission setup.

openPBRSurface factor-only diffuse transmission setup.

Note

A plain scalar on transmission or transmissionWeight is also used by classic transmission. To get a diffuse transmission result from a factor-only setup, pair it with a transmissionColor on the same shader.

Texture only

Color space: Raw

standardSurface · aiStandardSurface:
  packed RGBA case:
    aiImage.outAlpha  →  shader.transmission
    file.outAlpha     →  shader.transmission

  standalone grayscale case:
    aiImage.outColor / outColorR / outColorG / outColorB  →  shader.transmission
    file.outColor / outColorR / outColorG / outColorB     →  shader.transmission

openPBRSurface:
  packed RGBA case:
    aiImage.outAlpha  →  shader.transmissionWeight
    file.outAlpha     →  shader.transmissionWeight

  standalone grayscale case:
    aiImage.outColor / outColorR / outColorG / outColorB  →  shader.transmissionWeight
    file.outColor / outColorR / outColorG / outColorB     →  shader.transmissionWeight

Exports as diffuseTransmissionTexture. glTF reads diffuse transmission weight from the alpha channel, so standalone grayscale RGB sources are repacked to alpha during export.

When transmissionColor is textured too, the exporter supports both of these authoring patterns:

• Shared RGBA map: one texture node drives transmissionColor from outColor and drives transmission weight from outAlpha. The exporter keeps it as one packed glTF texture.
• Separate maps: one texture drives transmissionColor, and a separate grayscale or alpha map drives transmission weight. The exporter packs them into one glTF-compliant RGBA texture at export time.

standardSurfaceaiStandardSurfaceopenPBRSurface

standardSurface texture-only diffuse transmission setup with file and place2dTexture.

aiStandardSurface texture-only diffuse transmission setup with file and place2dTexture.

openPBRSurface texture-only diffuse transmission setup with file and place2dTexture.

Note

Use outAlpha when the same texture also carries diffuse transmission color in RGB. For a standalone grayscale weight map, outColor, outColorR, outColorG, and outColorB are all accepted.

Factor + texture

glTF computes: diffuseTransmissionFactor × diffuseTransmissionTexture

1. Connect the texture outAlpha → multiplyDivide.input1X.
2. Set the multiplier in multiplyDivide.input2X.
3. Connect multiplyDivide.outputX → shader.transmission (or transmissionWeight).

standardSurface · aiStandardSurface:
  packed RGBA case:
    texture.outAlpha  →  multiplyDivide.inputX/Y/Z  →  shader.transmission

  standalone grayscale case:
    texture.outColor / outColorR / outColorG / outColorB  →  multiplyDivide.inputX/Y/Z  →  shader.transmission

openPBRSurface:
  packed RGBA case:
    texture.outAlpha  →  multiplyDivide.inputX/Y/Z  →  shader.transmissionWeight

  standalone grayscale case:
    texture.outColor / outColorR / outColorG / outColorB  →  multiplyDivide.inputX/Y/Z  →  shader.transmissionWeight

The multiplier exports as diffuseTransmissionFactor.

Note

The exporter follows the actual upstream source plug and multiplyDivide lane. For standalone grayscale weight maps, it does not require any specific X/Y/Z lane as long as the connected channel carries the grayscale signal.

standardSurfaceaiStandardSurfaceopenPBRSurface

standardSurface factor-plus-texture diffuse transmission setup with file and place2dTexture.

aiStandardSurface factor-plus-texture diffuse transmission setup with file and place2dTexture.

openPBRSurface factor-plus-texture diffuse transmission setup with file and place2dTexture.

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Transmission color

Color factor only

Set transmissionColor directly on the shader.

Exports as diffuseTransmissionColorFactor.

Note

This color only participates in the diffuse transmission workflow when paired with a diffuse transmission weight setup.

Texture only

Color space: sRGB

standardSurface · aiStandardSurface · openPBRSurface:
  aiImage.outColor  →  shader.transmissionColor
  file.outColor     →  shader.transmissionColor

Exports as diffuseTransmissionColorTexture.

If the same texture also drives diffuse transmission weight through outAlpha, the exporter treats it as the packed RGBA case above instead of exporting two unrelated textures.

Color factor + texture (tint)

glTF computes: diffuseTransmissionColorFactor × diffuseTransmissionColorTexture

1. Connect texture.outColor → colorComposite.colorA.
2. Set the tint on colorComposite.colorB.
3. Set colorComposite to multiply mode.
4. Connect colorComposite.outColor → shader.transmissionColor.

standardSurface · aiStandardSurface · openPBRSurface:
  texture.outColor  →  colorComposite.colorA  →  shader.transmissionColor

The tint exports as diffuseTransmissionColorFactor.

Note

Changing the shader swatch while a texture is connected does not create a separate exported tint. Use the colorComposite setup above.

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UV transform

file nodes: set repeat, wrap, mirror, offset, and rotation on the connected place2dTexture.
aiImage nodes: wrap, scale, and offset export natively; rotation requires a place2dTexture.

UV set: assign via Maya's UV Set Editor or UV Linking - see UV Set Selection for node-type differences.

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Notes

• Diffuse transmission weight is a non-color workflow - use Raw color space.
• Diffuse transmission color is a color workflow - use sRGB.
• Packed RGBA diffuse transmission uses the texture alpha channel (outAlpha) for weight; standalone grayscale weight maps may use outColor, outColorR, outColorG, or outColorB because they carry the same value.
• Shared RGBA graphs and separate color-plus-weight graphs are both supported. Separate inputs are packed to one RGBA texture for glTF export when both diffuse transmission slots are textured.
• Standalone grayscale weight maps can pass through any multiplyDivide output lane; the exporter follows the real upstream plug instead of requiring a fixed X/Y/Z lane.
• standardSurface / aiStandardSurface use transmission for weight; openPBRSurface uses transmissionWeight.
• StingrayPBS does not export KHR_materials_diffuse_transmission.