code: func Frustum(left float64, right float64, bottom float64, top float64, zNear float64, zFar float64) {
  	C.glowFrustum(gpFrustum, (C.GLdouble)(left), (C.GLdouble)(right), (C.GLdouble)(bottom), (C.GLdouble)(top), (C.GLdouble)(zNear), (C.GLdouble)(zFar))
  }
docs: // multiply the current matrix by a perspective matrix