The Composite Texture feature provides the ability to combine one Texture with the content of another.
This is currently used to adjust the roughness of one Texture with the normal map details of another. This is useful for fighting a common artifact in real-time 3d rendering: Aliasing or shimmering of normal maps in the distance. It also maintains the specular size for a Material whose normal map is detailed when near to the camera, but uses the mip maps of the normalmap that might appear flat when farther away.
Setting up the Composite Texture to Modify the Roughness Depending on Normalmap Details
To configure a Texture to use the Composite Texture, assign the normal map (same size or higher res) to the Composite Texture property in your diffuse Texture. We often store the roughness in the diffuse alpha channel, but you can adjust any channel by changing the default settings.
The process assumes the Texture already contained a roughness value and adjusts the channel depending on the variation in the normal map to a rougher value (brighter).
If the Texture does not already contain info in the alpha channel, the process of modifying that particular channel will not work as no alpha channel means white. Instead, you must first adjust the Max Alpha property to set the source alpha to a constant value. If you directly hook up the alpha channel of the texture to the material roughness and your alpha channel was white (1, which is the default), then you can directly specify the roughness value as Max Alpha. The adjustment will be done to the texture content. The roughness adjustment will be done on top of that.
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| Normal Map | Composited Roughness Map |
You can set the Texture Editor to only show the alpha channel to verify your adjustments.
Compositing Properties
There are some additional properties that affect how the Composite Texture modifies the Texture's channel.
| Property | Description |
|---|---|
| Composite Texture Mode | Specifies which channel of the Texture (R, G, B, or A) the Composite Texture is used to modify. |
| Composite Power | Determines how much influence the Composite Texture has on the target channel. [1:default, <1 less influence, >1 more influence] |
Using the Composited Roughness Map
The Material makes use of the roughness map by sampling the alpha channel of the Texture.
You can combine multiple roughness in the shader by adding them and they should combine naturally.
Results
Issues
This feature only works if the UV layout of your normal map and the roughness map is the same. Note that this approximates the correct result. The result is isotropic, meaning any directionality of the normal map is not taken into account. Make sure you have large enough UV borders otherwise wrong content might creep in.