now the vertex's color is white, it is odd and unlike D3DFVF_DIFFUSE
why vertex's specular color is added to the texture
Moderators - Reputation: 23957
Posted 20 June 2013 - 12:54 AM
According to physics, when light hits a surface, some percentage of it is reflected off the surface, and some percentage is refracted into the surface.
Specular lighting simulates the reflected percentage of the input light. This light skims right off the surface without really touching it, so it's colour is usually unchanged (with the only exception being coloured metals, which behave differently).
Diffuse lighting simulates the refracted percentage of the input light. This light penetrates into the surface and some of it is absorbed (as heat, etc) into the surface. Different surfaces absorb different wavelengths (colours). After bouncing around inside the surface, some of the light is lucky enough to bounce back out of the surface, with it's colour changed.
What you see is the combination of both this reflected light and the refracted light, which is specular + diffuse.