Shader phong

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phong.mi
declare shader 
    color "phong" ( 
        color "ambient"   default 0 0 0, 
        color "diffuse"   default 1 1 1, 
	color "specular"  default 0 0 0, 
	scalar "exponent" default 30, 
        array light "lights" ) 
    version 1 
    apply material 
end declare 

phong.c
#include "shader.h" 
#include "miaux.h" 
 
struct phong { 
    miColor  ambient;   
    miColor  diffuse;   
    miColor  specular;  
    miScalar exponent; 
    int      i_light;   
    int      n_light;   
    miTag    light[1];  
}; 
 
DLLEXPORT 
int phong_version(void) { return 1; } 
 
DLLEXPORT 
miBoolean phong ( 
    miColor *result, miState *state, struct phong *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 exponent = *mi_eval_scalar(&params->exponent); 
    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_phong_specular_component(&sum, state, exponent, 
                                               &direction_toward_light, 
                                               specular, &light_color); 
        } 
        if (light_sample_count) 
            miaux_add_scaled_color(result, &sum, 1.0/light_sample_count); 
    }         
    return miTRUE; 
} 

phong_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_phong_specular_component( 
    miColor *result, miState *state, miScalar exponent, 
    miVector *direction_toward_light,  
    miColor *specular, miColor *light_color) 
{ 
    miScalar specular_amount = 
	mi_phong_specular(exponent, state, direction_toward_light); 
    if (specular_amount > 0.0) { 
	result->r += specular_amount * specular->r * light_color->r; 
	result->g += specular_amount * specular->g * light_color->g; 
	result->b += specular_amount * 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 23:40:08