Graphics Reference
In-Depth Information
Example 8-9
OpenGL ES 1.1 Fixed-Function Vertex Pipeline
(continued)
vec4 lighting_equation ( int i )
{
vec4 computed_color = vec4( c_zero, c_zero, c_zero,
c_zero );
vec3 h_vec;
float ndotl, ndoth;
float att_factor;
vec3 VPpli;
att_factor = c_one;
if ( light_state[i].position.w != c_zero )
{
float spot_factor;
vec3 att_dist;
// this is a point or spotlight
// we assume "w" values for PPli and V are the same
VPpli = light_state[i].position.xyz - p_eye.xyz;
if ( light_state[i].compute_distance_attenuation )
{
// compute distance attenuation
att_dist.x = c_one;
att_dist.z = dot ( VPpli, VPpli );
att_dist.y = sqrt ( att_dist.z ) ;
att_factor = c_one / dot ( att_dist,
light_state[i] .attenuation_factors );
}
VPpli = normalize ( VPpli );
if ( light_state[i].spot_cutoff_angle < 180.0 )
{
// compute spot factor
spot_factor = dot ( -VPpli,
light_state[i].spot_direction );
if( spot_factor >= cos ( radians (
light_state[i].spot_cutoff_angle ) ) )
spot_factor = pow ( spot_factor,
light_state[i].spot_exponent );
else
spot_factor = c_zero;
att_factor *= spot_factor;
}
}
(continues)
