Practical Algorithms for 3D Computer Graphics, 2nd Edition

468 11. Algorithms for procedural textures

Normals Normals Depressions

Raised bumps

Figure 11.10: Regular bumps and depressions formed by modula tin g the surface normal

of a solid object. The amplitude and direction of the modulation at a point p is

determined by its dista n c e from a sphere placed at the center of a texture cell. The

figure illustrates h ow the surface normal behaves in a cross-section through one of the

bumps. Bumps are shown on the left and depressions on the right.

to the texture cell axes, is given by:

∆n

′

=

p

′

− p

′

c

|p

′

− p

′

c

|

If |C − p

′

| < r then the point of interest lies inside the sph er e and the

normal will be pushed in the direction ...