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varying vec3 coords;
uniform vec3 active_color;
uniform float step_size;
uniform float density_scale;
uniform sampler3D soot_texture;
uniform sampler3D shadow_texture;
#ifdef USE_COBA
uniform sampler1D transfer_texture;
uniform sampler3D color_band_texture;
#endif
void main()
{
/* compute color and density from volume texture */
vec4 soot = texture3D(soot_texture, coords);
#ifndef USE_COBA
vec3 soot_color;
if (soot.a != 0) {
soot_color = active_color * soot.rgb / soot.a;
}
else {
soot_color = vec3(0, 0, 0);
}
float soot_density = density_scale * soot.a;
/* compute transmittance and alpha */
float soot_transmittance = pow(2.71828182846, -soot_density * step_size);
float soot_alpha = 1.0 - soot_transmittance;
/* shade */
float shadow = texture3D(shadow_texture, coords).r;
soot_color *= soot_transmittance * shadow;
/* premultiply alpha */
vec4 color = vec4(soot_alpha * soot_color, soot_alpha);
#else
float color_band = texture3D(color_band_texture, coords).r;
vec4 transfer_function = texture1D(transfer_texture, color_band);
vec4 color = transfer_function * density_scale;
#endif
gl_FragColor = color;
}
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