Often you'll want to change a texture's brightness or contrast in the rendered image, without having to modify the texture map itself.

During rendering, Indigo modifies the source texture data according to a quadratic formula with 3 parameters, A, B and C:

y = ax² + bx + c

x is the input value from the texture map, and y is the output value.

As a quick example for how this equation works: If we use A = 0, B = 1, C = 0 then the value is completely unchanged; this is therefore also the default.

A value – Quadratic

The A value scales the contribution of the quadratic (x²) term. This is typically not used, however it can be useful to adjust the contrast of a texture, with a value greater than 0, and/or a negative C value.

B value - Scale/Multiplier

Texture Scale (B value) of 2.

The B value scales the contribution of the linear (x) term. This is typically used to adjust the overall brightness (for example to reduce the maximum albedo of a texture, using a value of 0.8 or so), and can also be useful to adjust the contrast of a texture, with a value greater than 1, and/or a negative C value.

C value – Base/Constant

Texture constant (C value) of 0.2.

The C value is always added, regardless of the input texture amount; it therefore acts as a base or "floor" value. So for example if you have a completely black texture, and a C value of 0.5, it would appear as 50% grey.