Color Modulation
Color modulation is the process in which a texture is modified to add color. There are various strategies used by face libraries. In general, textures are split into color channels, and each channel is filled with a respective color.
Modes
There are 6 modes used in FFL.[1]
Constant
For textures where only one color replacement is needed. The red channel is colorized.
Used by: Beard (shape), Nose, Forehead, Hair, Fill
rgb = ColorR
a = 1.0
Texture Direct
For textures where no color modulation is required. The texture is “passed through” the shader with no modifications.
Used by: Makeup, Faceline, Mask
rgb = TextureRGB
a = TextureA
Rgb Layered
For textures where up to three colors need to be filled.
rgb = ColorR * TextureR + ColorG * TextureG + ColorB * TextureB
a = TextureA
Alpha
For textures where there is a single color that needs to be filled, and an alpha channel.
Used by: Mustache, Eyebrow, Mole, FaceLine (Wrinkle??), FaceBeard, Noseline
rgb = ColorR * TextureR
a = TextureR
Luminance Alpha
For textures that need to fill two colours, and alpha
Used by: Glass
r = ColorR * TextureG
a = TextureR
Alpha Opaque
Single-channel modulation with an opaque background.
Used by: Cap
rgb = ColorR * TextureR
a = 1.0