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layout(std140) uniform shadow_render_block {
mat4 ShadowMatrix[6];
vec4 lampPosition;
int layer;
float exponent;
};
uniform samplerCube shadowCube;
out vec4 FragColor;
vec3 octahedral_to_cubemap_proj(vec2 co)
{
co = co * 2.0 - 1.0;
vec2 abs_co = abs(co);
vec3 v = vec3(co, 1.0 - (abs_co.x + abs_co.y));
if ( abs_co.x + abs_co.y > 1.0 ) {
v.xy = (abs(co.yx) - 1.0) * -sign(co.xy);
}
return v;
}
void make_orthonormal_basis(vec3 N, out vec3 T, out vec3 B)
{
vec3 UpVector = abs(N.z) < 0.99999 ? vec3(0.0,0.0,1.0) : vec3(1.0,0.0,0.0);
T = normalize( cross(UpVector, N) );
B = cross(N, T);
}
#define NUM_SAMPLE 32
vec2 poisson_disc[32] = vec2[32](
vec2( 0.476, 0.854), vec2(-0.659, -0.670),
vec2( 0.905, -0.270), vec2( 0.215, -0.133),
vec2(-0.595, 0.242), vec2(-0.146, 0.519),
vec2( 0.108, -0.930), vec2( 0.807, 0.449),
vec2(-0.476, -0.854), vec2( 0.659, 0.670),
vec2(-0.905, 0.270), vec2(-0.215, 0.133),
vec2( 0.595, -0.242), vec2( 0.146, -0.519),
vec2(-0.108, 0.930), vec2(-0.807, -0.449),
vec2(-0.854, 0.476), vec2( 0.670, -0.659),
vec2( 0.270, 0.905), vec2( 0.133, 0.215),
vec2(-0.242, -0.595), vec2(-0.519, -0.146),
vec2( 0.930, 0.108), vec2(-0.449, 0.807),
vec2( 0.854, -0.476), vec2(-0.670, 0.659),
vec2(-0.270, -0.905), vec2(-0.133, -0.215),
vec2( 0.242, 0.595), vec2( 0.519, 0.146),
vec2(-0.930, -0.108), vec2( 0.449, -0.807)
);
/* Marco Salvi's GDC 2008 presentation about shadow maps pre-filtering techniques slide 24 */
float ln_space_prefilter(float w0, float x, float w1, float y)
{
return x + log(w0 + w1 * exp(y - x));
}
void main() {
const vec2 texelSize = vec2(1.0 / 512.0);
vec2 uvs = gl_FragCoord.xy * texelSize;
/* add a 2 pixel border to ensure filtering is correct */
uvs.xy *= 1.0 + texelSize * 2.0;
uvs.xy -= texelSize;
float pattern = 1.0;
/* edge mirroring : only mirror if directly adjacent
* (not diagonally adjacent) */
vec2 m = abs(uvs - 0.5) + 0.5;
vec2 f = floor(m);
if (f.x - f.y != 0.0) {
uvs.xy = 1.0 - uvs.xy;
}
/* clamp to [0-1] */
uvs.xy = fract(uvs.xy);
/* get cubemap vector */
vec3 cubevec = octahedral_to_cubemap_proj(uvs.xy);
vec3 T, B;
make_orthonormal_basis(cubevec, T, B);
/* get cubemap shadow value */
const float blur_radius = 5.0 / 512.0; /* Totally arbitrary */
const float weight = 1.0 / float(NUM_SAMPLE);
float accum = 0.0;
/* Poisson disc blur in log space. */
vec2 offsetvec = poisson_disc[0].xy * blur_radius;
float depth1 = texture(shadowCube, cubevec + offsetvec.x * T + offsetvec.y * B).r;
offsetvec = poisson_disc[1].xy * blur_radius;
float depth2 = texture(shadowCube, cubevec + offsetvec.x * T + offsetvec.y * B).r;
accum = ln_space_prefilter(weight, depth1, weight, depth2);
for (int i = 2; i < NUM_SAMPLE; ++i) {
vec2 offsetvec = poisson_disc[i].xy * blur_radius;
depth1 = texture(shadowCube, cubevec + offsetvec.x * T + offsetvec.y * B).r;
accum = ln_space_prefilter(1.0, accum, weight, depth1);
}
FragColor = vec4(accum, accum, accum, 1.0);
}
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