tjh@bu-cs.BU.EDU (Foxbat) (04/21/89)
Is there a mode to tell the geometry engine to do diffusely (and specular) shade a polygon even though its normal vector is pointing away from the light source. (Thus only getting ambient shading) Thanx... Tim tjh@bu-pub.bu.edu
thant@horus.SGI.COM (Thant Tessman) (04/21/89)
In article <29925@bu-cs.BU.EDU>, tjh@bu-cs.BU.EDU (Foxbat) writes: > Is there a mode to tell the geometry engine to do diffusely (and specular) > shade a polygon even though its normal vector is pointing away from the > light source. (Thus only getting ambient shading) > > Thanx... > Tim > tjh@bu-pub.bu.edu What you can do is create two versions of the object you want to draw. One with normals one way and the other with normals the other way. Define the polygons of each object so the vertices of each polygon are in counter-clockwise order when the normal is pointing at you (right-hand rule). That means that one object's vertices will be in opposite order of the other. Do backface(TRUE) and draw both objects. thant@sgi.com