最多支持到gl3,gl4以后无此函数。启用那一个需要使用glClientActiveTexture,glClientActiveTexture的序号值对应gl_MultiTexCoord后面的数字。
glClientActiveTexture selects the vertex array client state parameters to be modified by glTexCoordPointer, and enabled or disabled with glEnableClientState or glDisableClientState, respectively, when called with a parameter of GL_TEXTURE_COORD_ARRAY.
void glClientActiveTexture(GLenum texture)
texture
Specifies which texture unit to make active. The number of texture units is implementation dependent, but must be at least two. texture must be one of GL_TEXTUREi, where i ranges from 0 to the value of GL_MAX_TEXTURE_COORDS - 1, which is an implementation-dependent value. The initial value is GL_TEXTURE0.