6. Channels¶
Overpaint paints into named PBR channels. Twenty are built in:
| Channel | Default | Principled BSDF input |
|---|---|---|
| Colour | white | Base Color |
| Roughness | 0.5 | Roughness |
| Metalness | 0 | Metallic |
| Normal | flat normal | Normal (Normal Map) |
| Ambient Occlusion | white | — |
| Bump | grey | — |
| Height | grey | — |
| Emission | black | Emission Color |
| Opacity | white (opaque) | Alpha |
| Subsurface | 0 | Subsurface Weight |
| Specular | 0.5 | Specular IOR Level |
| Specular Color | white | Specular Tint |
| Coat | 0 | Coat Weight |
| Coat Roughness | 0.03 | Coat Roughness |
| Coat Color | white | Coat Tint |
| Anisotropy | 0 | Anisotropic |
| Anisotropy Angle | 0 | Anisotropic Rotation |
| Transmission | 0 | Transmission Weight |
| Sheen | 0 | Sheen Weight |
| Sheen Roughness | 0.5 | Sheen Roughness |
Colour, Roughness, Metalness, Normal and Ambient Occlusion are visible by default. OP Settings ▸ Channel visibility & custom channels toggles which channels appear in the panel, in the channel ribbon and on the material set's outputs; the ribbon itself (chapter 3.2) picks which of the visible channels a sublayer targets.
Extra channels. Opacity, Coat, Sheen and the other Principled channels are already built in. Show the ones you need in OP Settings ▸ Channel visibility & custom channels. Their defaults match the shader, so showing one does not change the look by itself.
Opacity controls surface transparency: white is solid, black is a hole, grey is see-through. Paint into the Opacity channel to cut holes or make decals. This is different from a layer's coverage (Erase Alpha reveals the layer below, it does not cut through the model).
Need a channel of your own, like Wear or Decal Mask? See chapter 18 for adding one.
Per-sublayer targeting. Every sublayer declares which channels it touches (top ribbon, that shows each time what selected item currently supports). A Paint sublayer can target only mask on MASK bus; a Colour sublayer can target Colour, Roughness, Metalness and other channels but not Mask; an Image sublayer can feed a different image to each channel. This is how one stroke of the multi-channel brush writes different values into different channels.