Vertex Colors usage missing in the spec

[migueldgg]

The glTF 2.0 spec used to state the following:

In addition to the material properties, if a primitive specifies a vertex color using the attribute semantic property COLOR_0, then this value acts as an additional linear multiplier to baseColor.

This sentence was removed in commit d6e9c90, making it unclear how vertex colors should be used in the final color computation.

It would be important to get this crucial bit of information back in the specification.

[mlimper]

TBH, it's not perfectly clear to me yet how vertex colors are assumed to be stored / used... both questions are connected.

storage: sRGB vs. linear?
use case: multiply brightness / ao vs. storing actual colors?

If someone has some insight into what was originally intended, that would probably be helpful in order to add more details / explanation to the spec

[lexaknyazev]

It's restored in the new spec draft (#1997).

TL;DR

• Base color is given by a baseColorTexture, that is 8-bit sRGB.
• When the texture slot is empty, the texture is defined as returning (1.0, 1.0, 1.0, 1.0) for all pixels.
• baseColorFactor and COLOR_0 values are linear multipliers.

[lexaknyazev]

The updated spec has been released.