Graphics Reference
In-Depth Information
Example 8-3
Spotlight
(continued)
if ( spot_factor >= cos ( radians (
light.spot_cutoff_angle ) ) )
spot_factor = pow ( spot_factor, light.spot_exponent );
else
spot_factor = c_zero;
// compute combined distance and spot attenuation factor
att_factor *= spot_factor;
}
if ( att_factor > c_zero )
{
// process lighting equation --> compute the light color
computed_color += ( light.ambient_color *
material.ambient_color );
ndotl = max ( c_zero, dot(normal, lightdir ) );
computed_color += ( ndotl * light.diffuse_color *
material.diffuse_color );
halfplane = normalize ( lightdir + vec3 ( c_zero, c_zero,
c_one ) );
ndoth = dot ( normal, halfplane );
if ( ndoth > c_zero )
{
computed_color += ( pow ( ndoth,
material.specular_exponent )*
material.specular_color *
light.specular_color );
}
// multiply color with computed attenuation
computed_color *= att_factor;
}
return computed_color;
}
// add a main function to make this into a valid vertex shader
We look at two examples that generate texture coordinates in a vertex
shader. The two examples are used when rendering shiny (i.e., reflective)
objects in a scene by generating a reflection vector and then using this
vector to compute a texture coordinate that indexes into a latitude-
longitude map (also called a sphere map) or a cubemap (represents six
