DirectX SDK

CONST_D3DSHADEMODE

The CONST_D3DSHADEMODE enumeration describes the supported shade mode for the D3DRENDERSTATE_SHADEMODE render state in the CONST_D3DRENDERSTATETYPE enumeration.

Enum CONST_D3DSHADEMODE
    D3DSHADE_FLAT         = 1
    D3DSHADE_GOURAUD      = 2
    D3DSHADE_PHONG        = 3
End Enum

D3DSHADE_FLAT: Flat shade mode. The color and specular component of the first vertex in the triangle are used to determine the color and specular component of the face. These colors remain constant across the triangle; that is, they aren't interpolated.
D3DSHADE_GOURAUD: Gouraud shade mode. The color and specular components of the face are determined by a linear interpolation between all three of the triangle's vertices.
D3DSHADE_PHONG: Phong shade mode is not currently supported.