| OCR Text |
Show 43 between the two vertices PO and PI is computed followed: as Nt=hNl +(1-t)*NO (4.4) where t=O at NO and t=l at Nl. . For t = 1/4, Nl/4 = O/4)*Nl (3/4)*NO. + The determination of the normal at is achieved in the the Gouraud between of same visible edges is the linear interpolation of these. two with edges consideration. Note a plane scan that the on the surface of of the computation The normal to the technique. two the as way point a polygon a shading at that point with surface at point a located the normals at the intersections passing through general. surface normal is normal point, the point quadratically under related to the vertex normal. From the determine the IV. 3 shading value at that at a function shading a will point. Shading function model. In yields approximated the computer graphics value intensity a shading function each of point on is defined the as body of function a an which object from the characteristics of the light source, the object, and the postion of the observer. By applying the point P (see Figure 4.5) equation (3.9) on an Sp=Cps] cos(i) object + d ] can + of the be previous chapter, computed W(i)*[ cos(s) ]in as: (4.5) the shading at a |
