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/* Bsdf direct light function */
/* in other word, how materials react to scene lamps */
/* Naming convention
* V View vector (normalized)
* N World Normal (normalized)
* L Outgoing Light Vector (Surface to Light in World Space) (normalized)
* Ldist Distance from surface to the light
* W World Pos
*/
/* ------------ Diffuse ------------- */
float direct_diffuse_point(vec3 N, vec4 l_vector)
{
float dist = l_vector.w;
vec3 L = l_vector.xyz / dist;
float bsdf = max(0.0, dot(N, L));
bsdf /= dist * dist;
return bsdf;
}
/* infinitly far away point source, no decay */
float direct_diffuse_sun(LightData ld, vec3 N)
{
float bsdf = max(0.0, dot(N, -ld.l_forward));
bsdf *= M_1_PI; /* Normalize */
return bsdf;
}
/* From Frostbite PBR Course
* Analytical irradiance from a sphere with correct horizon handling
* http://www.frostbite.com/wp-content/uploads/2014/11/course_notes_moving_frostbite_to_pbr.pdf */
float direct_diffuse_sphere(LightData ld, vec3 N, vec4 l_vector)
{
float dist = l_vector.w;
vec3 L = l_vector.xyz / dist;
float radius = max(ld.l_sizex, 0.0001);
float costheta = clamp(dot(N, L), -0.999, 0.999);
float h = min(ld.l_radius / dist , 0.9999);
float h2 = h*h;
float costheta2 = costheta * costheta;
float bsdf;
if (costheta2 > h2) {
bsdf = M_PI * h2 * clamp(costheta, 0.0, 1.0);
}
else {
float sintheta = sqrt(1.0 - costheta2);
float x = sqrt(1.0 / h2 - 1.0);
float y = -x * (costheta / sintheta);
float sinthetasqrty = sintheta * sqrt(1.0 - y * y);
bsdf = (costheta * acos(y) - x * sinthetasqrty) * h2 + atan(sinthetasqrty / x);
}
bsdf = max(bsdf, 0.0);
bsdf *= M_1_PI2;
return bsdf;
}
#ifdef USE_LTC
float direct_diffuse_rectangle(LightData ld, vec3 N, vec3 V, vec4 l_vector)
{
vec3 corners[4];
corners[0] = l_vector.xyz + ld.l_right * -ld.l_sizex + ld.l_up * ld.l_sizey;
corners[1] = l_vector.xyz + ld.l_right * -ld.l_sizex + ld.l_up * -ld.l_sizey;
corners[2] = l_vector.xyz + ld.l_right * ld.l_sizex + ld.l_up * -ld.l_sizey;
corners[3] = l_vector.xyz + ld.l_right * ld.l_sizex + ld.l_up * ld.l_sizey;
float bsdf = ltc_evaluate(N, V, mat3(1.0), corners);
bsdf *= M_1_2PI;
return bsdf;
}
#endif
#if 0
float direct_diffuse_unit_disc(vec3 N, vec3 L)
{
}
#endif
/* ----------- GGx ------------ */
vec3 direct_ggx_point(vec3 N, vec3 V, vec4 l_vector, float roughness, vec3 f0)
{
roughness = max(1e-3, roughness);
float dist = l_vector.w;
vec3 L = l_vector.xyz / dist;
float bsdf = bsdf_ggx(N, L, V, roughness);
bsdf /= dist * dist;
/* Fresnel */
float VH = max(dot(V, normalize(V + L)), 0.0);
return F_schlick(f0, VH) * bsdf;
}
vec3 direct_ggx_sun(LightData ld, vec3 N, vec3 V, float roughness, vec3 f0)
{
roughness = max(1e-3, roughness);
float bsdf = bsdf_ggx(N, -ld.l_forward, V, roughness);
float VH = dot(V, -ld.l_forward) * 0.5 + 0.5;
return F_schlick(f0, VH) * bsdf;
}
#ifdef USE_LTC
vec3 direct_ggx_sphere(LightData ld, vec3 N, vec3 V, vec4 l_vector, float roughness, vec3 f0)
{
vec3 L = l_vector.xyz / l_vector.w;
vec3 spec_dir = get_specular_reflection_dominant_dir(N, V, roughness);
vec3 P = line_aligned_plane_intersect(vec3(0.0), spec_dir, l_vector.xyz);
vec3 Px = normalize(P - l_vector.xyz) * ld.l_radius;
vec3 Py = cross(Px, L);
vec2 uv = lut_coords(dot(N, V), sqrt(roughness));
vec3 brdf_lut = texture(utilTex, vec3(uv, 1.0)).rgb;
vec4 ltc_lut = texture(utilTex, vec3(uv, 0.0)).rgba;
mat3 ltc_mat = ltc_matrix(ltc_lut);
// #define HIGHEST_QUALITY
#ifdef HIGHEST_QUALITY
vec3 Pxy1 = normalize( Px + Py) * ld.l_radius;
vec3 Pxy2 = normalize(-Px + Py) * ld.l_radius;
/* counter clockwise */
vec3 points[8];
points[0] = l_vector.xyz + Px;
points[1] = l_vector.xyz - Pxy2;
points[2] = l_vector.xyz - Py;
points[3] = l_vector.xyz - Pxy1;
points[4] = l_vector.xyz - Px;
points[5] = l_vector.xyz + Pxy2;
points[6] = l_vector.xyz + Py;
points[7] = l_vector.xyz + Pxy1;
float bsdf = ltc_evaluate_circle(N, V, ltc_mat, points);
#else
vec3 points[4];
points[0] = l_vector.xyz + Px;
points[1] = l_vector.xyz - Py;
points[2] = l_vector.xyz - Px;
points[3] = l_vector.xyz + Py;
float bsdf = ltc_evaluate(N, V, ltc_mat, points);
/* sqrt(pi/2) difference between square and disk area */
bsdf *= 1.25331413731;
#endif
bsdf *= brdf_lut.b; /* Bsdf intensity */
bsdf *= M_1_2PI * M_1_PI;
vec3 spec = F_area(f0, brdf_lut.xy) * bsdf;
return spec;
}
vec3 direct_ggx_rectangle(LightData ld, vec3 N, vec3 V, vec4 l_vector, float roughness, vec3 f0)
{
vec3 corners[4];
corners[0] = l_vector.xyz + ld.l_right * -ld.l_sizex + ld.l_up * ld.l_sizey;
corners[1] = l_vector.xyz + ld.l_right * -ld.l_sizex + ld.l_up * -ld.l_sizey;
corners[2] = l_vector.xyz + ld.l_right * ld.l_sizex + ld.l_up * -ld.l_sizey;
corners[3] = l_vector.xyz + ld.l_right * ld.l_sizex + ld.l_up * ld.l_sizey;
vec2 uv = lut_coords(dot(N, V), sqrt(roughness));
vec3 brdf_lut = texture(utilTex, vec3(uv, 1.0)).rgb;
vec4 ltc_lut = texture(utilTex, vec3(uv, 0.0)).rgba;
mat3 ltc_mat = ltc_matrix(ltc_lut);
float bsdf = ltc_evaluate(N, V, ltc_mat, corners);
bsdf *= brdf_lut.b; /* Bsdf intensity */
bsdf *= M_1_2PI;
vec3 spec = F_area(f0, brdf_lut.xy) * bsdf;
return spec;
}
#endif
#if 0
float direct_ggx_disc(vec3 N, vec3 L)
{
}
#endif
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