Motorola DSP96002 User 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