Color math should ideally always be in floats

Version: All, master

Platform(s): All, but mostly affects newer devices

Color math should ideally be done with float to support arbitrary precision. It’s somewhat common to have 10-bpc and 12-bpc displays, and HDR color math often needs 16 bits per channel. float aka Single precision floats have 23 bits of significant binary digits which is plenty for colors.

Floats also avoid the problem of clipping, as colors above 1 still work fine. Even if they clip when displayed, if the brightness is reduced for the whole image, the brightness differences in bright areas is preserved when using floats.

Floats are also more friendly to the user. It’s easier to understand that “0.5” is 50% strength than “127”.

Xenko already has Color3 and Color4 classes which already work with floats. However, there’s not much point to Color3 in my opinion. You can just have constructors and methods that take the alpha value as an optional parameter for use cases that don’t need it.

If it were up to me, I’d do the following:

1. Modify Color4 to make the alpha value optional. Consider deprecating Color3. This isn’t a breaking change.

2. Rename Color to Color8 and consider deprecating it. This is a breaking change.

3. Rename Color4 to Color. This is a breaking change.

These don’t all necessarily have to be done at once. In fact it may be preferable to leave a time gap between 2 and 3 to avoid people using “Color” in their code and having the implementation change without them knowing.

Obviously it’s the Xenko team’s decision of what to do, but I do think that something should be done, since color math being done with bytes is not ideal. Having a “Color” class with nothing after the name implies that it’s the recommended / default choice.

[Kryptos-FR]

I think you did not understand the point of Color3.

[aaronfranke]

@Kryptos-FR No, using optional parameters, it would be done like this:

public Color4(float red, float green, float blue, float alpha = 1.0f)
{
        R = red;
        G = green;
        B = blue;
        A = alpha;
}

Then you can write code in either of these two ways:

new Color4(0.1f, 0.2f, 0.3f); // Alpha is 1.0
new Color4(0.1f, 0.2f, 0.3f, 0.4f); // Alpha is 0.4