Shader cook_torrance

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cook_torrance.mi
declare shader 
    color "cook_torrance" ( 
        color  "ambient"                  default 0 0 0, 
        color  "diffuse"                  default 1 1 1, 
	color  "specular"                 default 0 0 0, 
	scalar "average_microfacet_slope" default .2, 
	color  "index_of_refraction"      default 1 1 1, 
        array light "lights" ) 
    version 1 
    apply material 
end declare 

cook_torrance.c
#include "shader.h" 
#include "miaux.h" 
 
struct cook_torrance { 
    miColor  ambient;   
    miColor  diffuse;   
    miColor  specular;  
    miScalar avg_microfacet_slope; 
    miColor  index_of_refraction;      
    int      i_light;  
    int      n_light;  
    miTag    light[1]; 
}; 
 
DLLEXPORT 
int cook_torrance_version(void) { return 1; } 
 
DLLEXPORT 
miBoolean cook_torrance (  
    miColor *result, miState *state, struct cook_torrance *params  ) 
{ 
    int i, light_count, light_sample_count; 
    miColor sum, light_color; 
    miVector direction_toward_light; 
    miScalar dot_nl; 
    miTag *light; 
 
    miColor *diffuse              = mi_eval_color(&params->diffuse); 
    miColor *specular             = mi_eval_color(&params->specular); 
    miScalar avg_microfacet_slope = *mi_eval_scalar(&params->avg_microfacet_slope); 
    miColor *index_of_refraction  = mi_eval_color(&params->index_of_refraction); 
    miaux_light_array(&light, &light_count, state, 
                      &params->i_light, &params->n_light, params->light); 
    *result = *mi_eval_color(&params->ambient); 
 
    for (i = 0; i < light_count; i++, light++) { 
        miaux_set_channels(&sum, 0); 
        light_sample_count = 0; 
        while (mi_sample_light(&light_color, &direction_toward_light, &dot_nl,  
                               state, *light, &light_sample_count)) { 
            miaux_add_diffuse_component(&sum, dot_nl, diffuse, &light_color); 
            miaux_add_cook_torrance_specular_component( 
                &sum, state, avg_microfacet_slope, index_of_refraction,  
                direction_toward_light, specular, &light_color); 
        } 
        if (light_sample_count) 
            miaux_add_scaled_color(result, &sum, 1.0/light_sample_count); 
    } 
    return miTRUE; 
} 

cook_torrance_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; 
} 
 
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_cook_torrance_specular_component( 
    miColor *result, miState *state, 
    miScalar roughness, miColor *ior, 
    miVector direction_toward_light, 
    miColor *specular, miColor *light_color) 
{ 
    miColor specular_reflection_color; 
    if (mi_cooktorr_specular(&specular_reflection_color, &state->dir,  
			     &direction_toward_light, 
			     &state->normal, roughness, ior)) { 
	result->r += specular_reflection_color.r * specular->r * light_color->r; 
	result->g += specular_reflection_color.g * specular->g * light_color->g; 
	result->b += specular_reflection_color.b * specular->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 23:40:10