| OCR Text |
Show 2 If there is no normal map reference, the calculated surface normal is pia d into the ray intersection record. If there is a normal map reference, the int rse tion coordinate is transformed into a map coordinate which is used to retrieve th perturbation from the normal map. Before the perturbation can be applied to the surface normal, the two tangent vectors, pu and pv, must be calculated. These two vectors and the surface normal are mutually orthogonal. The surface normal can now be perturbed fu units in the direction of pu, and fv units in the direction of pv. A diagram of this calculation is shown in Figure 13. Figure 14 shows several nortnal peturbation texture maps. Figure 15 shows the same texture maps applied to smooth shaded quadric objects. IF ( object.surface.normaltexture THEN ray.internorm := normal ELSE ray.internorm := NIL) normal + (fu * pu) - (fv * pv); Figure 13: Implementation of Normal Texture Mapping |
