THREE.Color: added sRGB conversion methods

[WestLangley]

I expect these methods will, at some point, replace convertGammaToLinear(), etc.

[donmccurdy]

+1 for the clearer naming of convert* methods.

Just to confirm here, the power of 2.4 is chosen to approximate a gamma factor of 2.2, yes? That assumption might benefit from a comment in the code and/or docs.

It seems a little weird to diverge from our existing renderer.gammaFactor default of 2.0, but I agree this value makes much more sense... probably we should change that default as well.

[WestLangley]

No, you have a misunderstanding. Have a look at the Wikipedia sRGB article, and read about the sRGB transfer function.

gammaInput and gammaOutput (and the gamma nomenclature) will be deprecated. We will instead refer to the sRGB color space.

[donmccurdy]

It's this bit...

It is often casually stated that the decoding gamma for sRGB data is 2.2, yet the above transform shows an exponent of 2.4 ... it goes from gamma = 1 at zero to a gamma of 2.4 at maximum intensity with a median value being close to 2.2. The transformation was designed to approximate a gamma of about 2.2.

...that I find non-obvious. But assuming a change to from gamma nomenclature to renderer.outputColorspace=THREE.sRGBColorSpace would also mean deprecating renderer.gammaFactor, I think this all makes sense.

[06wj]

I think it should be

copySRGBToLinear: function () {

    function SRGBToLinear( c ) {

        return ( c < 0.04045 ) ? c * 0.0773993808 : Math.pow( c * 0.9478672986 + 0.0521327014, 2.4 );

    }

    return function( color ) {
       this.r = SRGBToLinear( color.r );
       this.g = SRGBToLinear( color.g );
       this.b = SRGBToLinear( color.b );

       return this;
   };
}()

so that it will not create function in every call.

[WestLangley]

Oops. Thanks!

[WestLangley]

r95 milestone? How about right now?

[mrdoob]

Okay 😛

[mrdoob]

Thanks!