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lambert_steps.mi
declare shader
color "lambert_steps" (
color "ambient" default 0 0 0,
color "diffuse" default 1 1 1,
integer "steps" default 3,
array light "lights" )
version 1
apply material
end declare
lambert_steps.c
#include "shader.h"
#include "miaux.h"
struct lambert_steps {
miColor ambient;
miColor diffuse;
miInteger steps;
int i_light;
int n_light;
miTag light[1];
};
DLLEXPORT
int lambert_steps_version(void) { return 1; }
DLLEXPORT
miBoolean lambert_steps (
miColor *result, miState *state, struct lambert_steps *params )
{
int i, light_count, light_sample_count;
miColor sum, light_color;
miScalar dot_nl;
miTag *light;
miColor *diffuse = mi_eval_color(¶ms->diffuse);
miInteger steps = *mi_eval_integer(¶ms->steps);
miaux_light_array(&light, &light_count, state,
¶ms->i_light, ¶ms->n_light, params->light);
*result = *mi_eval_color(¶ms->ambient);
for (i = 0; i < light_count; i++, light++) {
miaux_set_channels(&sum, 0);
light_sample_count = 0;
while (mi_sample_light(&light_color, NULL, &dot_nl,
state, *light, &light_sample_count)) {
dot_nl = miaux_quantize(dot_nl, steps);
miaux_add_diffuse_component(&sum, dot_nl, diffuse, &light_color);
}
if (light_sample_count)
miaux_add_scaled_color(result, &sum, 1.0/light_sample_count);
}
return miTRUE;
}
lambert_steps_util.c
void miaux_light_array(miTag **lights, int *light_count, miState *state,
int *offset_param, int *count_param, miTag *lights_param)
{
int array_offset = *mi_eval_integer(offset_param);
*light_count = *mi_eval_integer(count_param);
*lights = mi_eval_tag(lights_param) + array_offset;
}
void miaux_set_channels(miColor *c, miScalar new_value)
{
c->r = c->g = c->b = c->a = new_value;
}
miScalar miaux_quantize(miScalar value, miInteger count)
{
miScalar q = (miScalar)count;
if (count < 2)
return q;
else
return (miScalar)((int)(value * q) / (q - 1));
}
void miaux_add_diffuse_component(
miColor *result,
miScalar light_and_surface_cosine,
miColor *diffuse, miColor *light_color)
{
result->r += light_and_surface_cosine * diffuse->r * light_color->r;
result->g += light_and_surface_cosine * diffuse->g * light_color->g;
result->b += light_and_surface_cosine * diffuse->b * light_color->b;
}
void miaux_add_scaled_color(miColor *result, miColor *color, miScalar scale)
{
result->r += color->r * scale;
result->g += color->g * scale;
result->b += color->b * scale;
}
22 April 2008 23:40:02