The layer_RGBA shader can be used to linearly layer up to eight shaders together, enabling you to create complex shading effects. Layers are applied in order (bottom to top) according to a blending mode specified in the operation. The layer alpha can optionally be a separate input. A use for this shader could include adding text to an image for example.
Enable (1-8)
Enable/disable the layer entirely.
Swap Inputs (1-8)
Swaps the input of the current and the selected layers.
Move (1-8)
Moves the current layer in place of the selected layer, pushing the other layers up or down, changing the order of the layers. For instance if layer 2 is moved in place of layer 5, the new order is (bottom to top): layer 1, layer 3, layer 4, layer 5, layer 2, layer 6, layer 7, layer 8.
Name (1-8)
Layer name.
Input (1-8)
Input value for Layer.
Mix (1-8)
Controls the amount of blending between shaders.
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0
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0.5
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1 (default)
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You may need to insert a range shader when connecting a bitmap to mix.
Operation (1-8)
The blending mode for the current layer. They emulate all of Nuke and Photoshop's modes. In the formulas, A (layer_1) is the upstream intermediate result, and B (layer_2) is the current layer.
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Atop: A * B.a + B * (1 - A.a)
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Average: (A + B) / 2
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Cojoint Over: A if A.a > B.a else A + B * (1 - A.a) /B.a
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Color Burn: 1 - (1 - A) / B
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Color Dodge: A/ (1 - B)
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Difference: abs(A - B)
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Disjoint Over: A + B * (1 - A.a) / B.a, A + B if A.a + B.a < 1
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Divide: A / B, 0 if A and B < 0, else A if B < epsilon
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Exclusion: A + B - 2 * A * B
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From: B - A
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Geometric: 2 * A * B / (A + B)
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Glow: B2 / (1 - A)
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Hard Light: 1 - 2 * (1 - A) * (1 - B), 2 * A * B if A < 0.5
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Hard Light: 1 - 2 * (1 - A) * (1 - B), 2 * A * B if A < 0.5
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Hypot Diagonal: hypot_diagonal: √(A2 + B2)
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In: in: A * B.a
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Linear Light: (B< 0.5) ? A + 2* B- 1: A + 2 * (B - 0.5)
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Mask: B * A.a
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Matte: A * A.a + B * (1 - A.a)
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Max: max(A, B)
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Min: min(A, B)
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Minus: A - B
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Multiply: A * B, A if A and B < 0
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Negation: 1 - abs(1 - A - B)
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Out: A * (1 - B.a)
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Over: A + B * (1 - A.a)
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Overlay: hardlight(B, A)
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Overwrite: B
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Phoenix: min(A, B) - max(A, B) +1
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Pin Light: B < 0.5 ? min(A, 2 * B) : max(A, 2 * (B - 0.5)
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Plus: A + B
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Reflect: A2 / (1 - B)
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Screen: A + B - A * B if A and B in 0..1, else max(A, B)
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Soft Light: Softer version of hard_light
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Stencil: B * (1 - A.a)
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Subtract: A + B - 1
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Under: A * (1 - B.a) + B
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Vivid Light: B < 0.5 ? color_burn(A, 2 * B) : color_dodge(A, 2* (B - 0.5)
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XOR: A * (1 - B.a) + B * (1 - A.a)
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Normal Map
It is possible to blend multiple normal maps using the normal map blending operation.
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Normal map->Layer 1 Input
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Normal map->Layer 2 Input
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Normal map 1 & 2 combined
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Rendered result
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Alpha Operation (1-8)
Optional alpha value for Layer.
Result: The alpha is computed in the same way as the other color channels (follows the "operation" for the RGB channel).
Preserve: Keeps the old alpha value ( A.a ).
Overwrite: The alpha channel is overwritten by the alpha of the current layer ( B.a ).
Mask: Calculated as: A.a + B.a - A.a * B.a.
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Atop
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Average
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Cojoint Over
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Color Burn
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Color Dodge
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Difference
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Disjoint Over
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Divide
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Exclusion
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From
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Geometric
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Glow
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Hard Light
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Hard Mix
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Hypot Diagonal
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In
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Linear Light
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Mask
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Matte
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Max
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Min
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Minus
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Multiply
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Negation
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Out
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Over
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Overlay
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Overwrite
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Phoenix
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Pin Light
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Plus
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Reflect
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Screen
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Soft Light
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Stencil
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Subtract
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Under
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Vivid Light
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XOR
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Clamp
Clamp all intermediate results to [0,1].
Example of layer_RGBA shader used to layer Arnold graffiti texture onto brick texture