Shader lambert_steps

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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(&params->diffuse); 
    miInteger steps = *mi_eval_integer(&params->steps); 
    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, 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