COLOR1 is actually smoothed vertex normal data. Its function is to replace the original vertex normals of the model, using the smoothed vertex normals to extend outwards, thereby achieving the stroke effect. The smoothed vertex normals are first compressed using an octahedral compression algorithm, then transformed in tangent space, and finally stored in TEXCOORD.
COLOR1 is actually smoothed vertex normal data. Its function is to replace the original vertex normals of the model, using the smoothed vertex normals to extend outwards, thereby achieving the stroke effect. The smoothed vertex normals are first compressed using an octahedral compression algorithm, then transformed in tangent space, and finally stored in TEXCOORD.