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uniform sampler2D irradianceGrid;
#ifdef IRRADIANCE_CUBEMAP
struct IrradianceData {
vec3 color;
};
#elif defined(IRRADIANCE_SH_L2)
struct IrradianceData {
vec3 shcoefs[9];
};
#else /* defined(IRRADIANCE_HL2) */
struct IrradianceData {
vec3 cubesides[3];
};
#endif
IrradianceData load_irradiance_cell(int cell, vec3 N)
{
/* Keep in sync with diffuse_filter_probe() */
#if defined(IRRADIANCE_CUBEMAP)
#define AMBIANT_CUBESIZE 8
ivec2 cell_co = ivec2(AMBIANT_CUBESIZE);
int cell_per_row = textureSize(irradianceGrid, 0).x / cell_co.x;
cell_co.x *= cell % cell_per_row;
cell_co.y *= cell / cell_per_row;
vec2 texelSize = 1.0 / vec2(AMBIANT_CUBESIZE);
vec2 uvs = mapping_octahedron(N, texelSize);
uvs *= vec2(AMBIANT_CUBESIZE) / vec2(textureSize(irradianceGrid, 0));
uvs += vec2(cell_co) / vec2(textureSize(irradianceGrid, 0));
IrradianceData ir;
ir.color = texture(irradianceGrid, uvs).rgb;
#elif defined(IRRADIANCE_SH_L2)
ivec2 cell_co = ivec2(3, 3);
int cell_per_row = textureSize(irradianceGrid, 0).x / cell_co.x;
cell_co.x *= cell % cell_per_row;
cell_co.y *= cell / cell_per_row;
ivec3 ofs = ivec3(0, 1, 2);
IrradianceData ir;
ir.shcoefs[0] = texelFetch(irradianceGrid, cell_co + ofs.xx, 0).rgb;
ir.shcoefs[1] = texelFetch(irradianceGrid, cell_co + ofs.yx, 0).rgb;
ir.shcoefs[2] = texelFetch(irradianceGrid, cell_co + ofs.zx, 0).rgb;
ir.shcoefs[3] = texelFetch(irradianceGrid, cell_co + ofs.xy, 0).rgb;
ir.shcoefs[4] = texelFetch(irradianceGrid, cell_co + ofs.yy, 0).rgb;
ir.shcoefs[5] = texelFetch(irradianceGrid, cell_co + ofs.zy, 0).rgb;
ir.shcoefs[6] = texelFetch(irradianceGrid, cell_co + ofs.xz, 0).rgb;
ir.shcoefs[7] = texelFetch(irradianceGrid, cell_co + ofs.yz, 0).rgb;
ir.shcoefs[8] = texelFetch(irradianceGrid, cell_co + ofs.zz, 0).rgb;
#else /* defined(IRRADIANCE_HL2) */
ivec2 cell_co = ivec2(3, 2);
int cell_per_row = textureSize(irradianceGrid, 0).x / cell_co.x;
cell_co.x *= cell % cell_per_row;
cell_co.y *= cell / cell_per_row;
ivec3 is_negative = ivec3(step(0.0, -N));
IrradianceData ir;
ir.cubesides[0] = texelFetch(irradianceGrid, cell_co + ivec2(0, is_negative.x), 0).rgb;
ir.cubesides[1] = texelFetch(irradianceGrid, cell_co + ivec2(1, is_negative.y), 0).rgb;
ir.cubesides[2] = texelFetch(irradianceGrid, cell_co + ivec2(2, is_negative.z), 0).rgb;
#endif
return ir;
}
/* http://seblagarde.wordpress.com/2012/01/08/pi-or-not-to-pi-in-game-lighting-equation/ */
vec3 spherical_harmonics_L1(vec3 N, vec3 shcoefs[4])
{
vec3 sh = vec3(0.0);
sh += 0.282095 * shcoefs[0];
sh += -0.488603 * N.z * shcoefs[1];
sh += 0.488603 * N.y * shcoefs[2];
sh += -0.488603 * N.x * shcoefs[3];
return sh;
}
vec3 spherical_harmonics_L2(vec3 N, vec3 shcoefs[9])
{
vec3 sh = vec3(0.0);
sh += 0.282095 * shcoefs[0];
sh += -0.488603 * N.z * shcoefs[1];
sh += 0.488603 * N.y * shcoefs[2];
sh += -0.488603 * N.x * shcoefs[3];
sh += 1.092548 * N.x * N.z * shcoefs[4];
sh += -1.092548 * N.z * N.y * shcoefs[5];
sh += 0.315392 * (3.0 * N.y * N.y - 1.0) * shcoefs[6];
sh += -1.092548 * N.x * N.y * shcoefs[7];
sh += 0.546274 * (N.x * N.x - N.z * N.z) * shcoefs[8];
return sh;
}
vec3 hl2_basis(vec3 N, vec3 cubesides[3])
{
vec3 irradiance = vec3(0.0);
vec3 n_squared = N * N;
irradiance += n_squared.x * cubesides[0];
irradiance += n_squared.y * cubesides[1];
irradiance += n_squared.z * cubesides[2];
return irradiance;
}
vec3 compute_irradiance(vec3 N, IrradianceData ird)
{
#if defined(IRRADIANCE_CUBEMAP)
return ird.color;
#elif defined(IRRADIANCE_SH_L2)
return spherical_harmonics_L2(N, ird.shcoefs);
#else /* defined(IRRADIANCE_HL2) */
return hl2_basis(N, ird.cubesides);
#endif
}
vec3 get_cell_color(ivec3 localpos, ivec3 gridres, int offset, vec3 ir_dir)
{
/* Keep in sync with update_irradiance_probe */
int cell = offset + localpos.z + localpos.y * gridres.z + localpos.x * gridres.z * gridres.y;
IrradianceData ir_data = load_irradiance_cell(cell, ir_dir);
return compute_irradiance(ir_dir, ir_data);
}
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