Motorola DSP96002 - Manual (Page 586)

MOTOROLA DSP96002 USER’S MANUAL B-67
R Direction vector of reflection of the point source from the
object R={Rx,Ry,Rz}
V Direction vector from the object to the viewpoint
Ks Specular reflection constant 0<= Ks <= 1.0
It should be noted that all vectors are normalized to unit magnitude.
The illumination can be described several ways depending on the complexity of the object and light source:
I=Ip Kd L*N Diffuse reflection
I=Ia Ka + Ip Kd L*N Ambient lighting and diffuse reflection
I=Ia Ka + Ip(Kd L*N + Ks(R*V)**n)
Ambient lighting, diffuse reflection and
specular reflection (Phong model)
In the above equations, * represents a vector dot product such as L*N = LxNx+LyNy+LzNz and ** repre-
sents exponentiation.
Since the dot product of two normalized vectors is less than or equal to one, the term Ks(R*V)**n is less
than one. The value of this term is found by using a 256 element lookup table with 256.0(R*V) as an index.
The value of n is an arbitrary term that is fixed for the algorithm and depends on empirical conditions.
X memory Y memory
vec R0
→
Rx Vx
Ry Vy
Rz Vz
Lx Nx
Ly Ny
Lz Nz
ktbl R4
→
256.0
address of spctbl
Kd
Ip
Ia
Ka