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// Functions related to lighting
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-// This returns the G_GGX function divided by 2 cos_theta_m, where in practice cos_theta_m is either N.L or N.V.
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-// We're dividing this factor off because the overall term we'll end up looks like
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-// (see, for example, the first unnumbered equation in B. Burley, "Physically Based Shading at Disney", SIGGRAPH 2012):
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-//
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-// F(L.V) D(N.H) G(N.L) G(N.V) / (4 N.L N.V)
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-//
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-// We're basically regouping this as
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-//
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-// F(L.V) D(N.H) [G(N.L)/(2 N.L)] [G(N.V) / (2 N.V)]
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-//
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-// and thus, this function implements the [G(N.m)/(2 N.m)] part with m = L or V.
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-//
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-// The contents of the D and G (G1) functions (GGX) are taken from
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-// E. Heitz, "Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs", J. Comp. Graph. Tech. 3 (2) (2014).
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-// Eqns 71-72 and 85-86 (see also Eqns 43 and 80).
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-
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-float G_GGX_2cos(float cos_theta_m, float alpha) {
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- // Schlick's approximation
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- // C. Schlick, "An Inexpensive BRDF Model for Physically-based Rendering", Computer Graphics Forum. 13 (3): 233 (1994)
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- // Eq. (19), although see Heitz (2014) the about the problems with his derivation.
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- // It nevertheless approximates GGX well with k = alpha/2.
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- float k = 0.5 * alpha;
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- return 0.5 / (cos_theta_m * (1.0 - k) + k);
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-
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- // float cos2 = cos_theta_m * cos_theta_m;
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- // float sin2 = (1.0 - cos2);
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- // return 1.0 / (cos_theta_m + sqrt(cos2 + alpha * alpha * sin2));
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-}
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-
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float D_GGX(float cos_theta_m, float alpha) {
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float alpha2 = alpha * alpha;
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float d = 1.0 + (alpha2 - 1.0) * cos_theta_m * cos_theta_m;
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return alpha2 / (M_PI * d * d);
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}
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-float G_GGX_anisotropic_2cos(float cos_theta_m, float alpha_x, float alpha_y, float cos_phi, float sin_phi) {
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- float cos2 = cos_theta_m * cos_theta_m;
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- float sin2 = (1.0 - cos2);
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- float s_x = alpha_x * cos_phi;
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- float s_y = alpha_y * sin_phi;
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- return 1.0 / max(cos_theta_m + sqrt(cos2 + (s_x * s_x + s_y * s_y) * sin2), 0.001);
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+// From Earl Hammon, Jr. "PBR Diffuse Lighting for GGX+Smith Microsurfaces" https://www.gdcvault.com/play/1024478/PBR-Diffuse-Lighting-for-GGX
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+float V_GGX(float NdotL, float NdotV, float alpha) {
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+ return 0.5 / mix(2.0 * NdotL * NdotV, NdotL + NdotV, alpha);
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}
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float D_GGX_anisotropic(float cos_theta_m, float alpha_x, float alpha_y, float cos_phi, float sin_phi) {
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- float cos2 = cos_theta_m * cos_theta_m;
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- float sin2 = (1.0 - cos2);
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- float r_x = cos_phi / alpha_x;
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- float r_y = sin_phi / alpha_y;
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- float d = cos2 + sin2 * (r_x * r_x + r_y * r_y);
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- return 1.0 / max(M_PI * alpha_x * alpha_y * d * d, 0.001);
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+ float alpha2 = alpha_x * alpha_y;
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+ highp vec3 v = vec3(alpha_y * cos_phi, alpha_x * sin_phi, alpha2 * cos_theta_m);
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+ highp float v2 = dot(v, v);
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+ float w2 = alpha2 / v2;
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+ float D = alpha2 * w2 * w2 * (1.0 / M_PI);
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+ return D;
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+}
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+
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+float V_GGX_anisotropic(float alpha_x, float alpha_y, float TdotV, float TdotL, float BdotV, float BdotL, float NdotV, float NdotL) {
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+ float Lambda_V = NdotL * length(vec3(alpha_x * TdotV, alpha_y * BdotV, NdotV));
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+ float Lambda_L = NdotV * length(vec3(alpha_x * TdotL, alpha_y * BdotL, NdotL));
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+ return 0.5 / (Lambda_V + Lambda_L);
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}
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float SchlickFresnel(float u) {
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@@ -58,14 +32,6 @@ float SchlickFresnel(float u) {
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return m2 * m2 * m; // pow(m,5)
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}
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-float GTR1(float NdotH, float a) {
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- if (a >= 1.0)
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- return 1.0 / M_PI;
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- float a2 = a * a;
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- float t = 1.0 + (a2 - 1.0) * NdotH * NdotH;
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- return (a2 - 1.0) / (M_PI * log(a2) * t);
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-}
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-
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vec3 F0(float metallic, float specular, vec3 albedo) {
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float dielectric = 0.16 * specular * specular;
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// use albedo * metallic as colored specular reflectance at 0 angle for metallic materials;
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@@ -87,7 +53,7 @@ void light_compute(vec3 N, vec3 L, vec3 V, float A, vec3 light_color, float atte
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float rim, float rim_tint,
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#endif
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#ifdef LIGHT_CLEARCOAT_USED
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- float clearcoat, float clearcoat_gloss,
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+ float clearcoat, float clearcoat_roughness, vec3 vertex_normal,
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#endif
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#ifdef LIGHT_ANISOTROPY_USED
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vec3 B, vec3 T, float anisotropy,
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@@ -115,11 +81,11 @@ void light_compute(vec3 N, vec3 L, vec3 V, float A, vec3 light_color, float atte
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float NdotV = dot(N, V);
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float cNdotV = max(NdotV, 0.0);
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-#if defined(DIFFUSE_BURLEY) || defined(SPECULAR_BLINN) || defined(SPECULAR_SCHLICK_GGX) || defined(LIGHT_CLEARCOAT_USED)
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+#if defined(DIFFUSE_BURLEY) || defined(SPECULAR_SCHLICK_GGX) || defined(LIGHT_CLEARCOAT_USED)
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vec3 H = normalize(V + L);
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#endif
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-#if defined(SPECULAR_BLINN) || defined(SPECULAR_SCHLICK_GGX) || defined(LIGHT_CLEARCOAT_USED)
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+#if defined(SPECULAR_SCHLICK_GGX)
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float cNdotH = clamp(A + dot(N, H), 0.0, 1.0);
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#endif
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@@ -203,26 +169,7 @@ void light_compute(vec3 N, vec3 L, vec3 V, float A, vec3 light_color, float atte
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// D
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-#if defined(SPECULAR_BLINN)
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-
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- //normalized blinn
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- float shininess = exp2(15.0 * (1.0 - roughness) + 1.0) * 0.25;
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- float blinn = pow(cNdotH, shininess);
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- blinn *= (shininess + 2.0) * (1.0 / (8.0 * M_PI));
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-
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- specular_light += light_color * attenuation * specular_amount * blinn * f0 * orms_unpacked.w;
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-
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-#elif defined(SPECULAR_PHONG)
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-
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- vec3 R = normalize(-reflect(L, N));
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- float cRdotV = clamp(A + dot(R, V), 0.0, 1.0);
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- float shininess = exp2(15.0 * (1.0 - roughness) + 1.0) * 0.25;
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- float phong = pow(cRdotV, shininess);
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- phong *= (shininess + 1.0) * (1.0 / (8.0 * M_PI));
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-
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- specular_light += light_color * attenuation * specular_amount * phong * f0 * orms_unpacked.w;
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-
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-#elif defined(SPECULAR_TOON)
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+#if defined(SPECULAR_TOON)
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vec3 R = normalize(-reflect(L, N));
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float RdotV = dot(R, V);
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@@ -236,24 +183,21 @@ void light_compute(vec3 N, vec3 L, vec3 V, float A, vec3 light_color, float atte
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#elif defined(SPECULAR_SCHLICK_GGX)
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// shlick+ggx as default
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-
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+ float alpha_ggx = roughness * roughness;
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#if defined(LIGHT_ANISOTROPY_USED)
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- float alpha_ggx = roughness * roughness;
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float aspect = sqrt(1.0 - anisotropy * 0.9);
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float ax = alpha_ggx / aspect;
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float ay = alpha_ggx * aspect;
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float XdotH = dot(T, H);
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float YdotH = dot(B, H);
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float D = D_GGX_anisotropic(cNdotH, ax, ay, XdotH, YdotH);
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- float G = G_GGX_anisotropic_2cos(cNdotL, ax, ay, XdotH, YdotH) * G_GGX_anisotropic_2cos(cNdotV, ax, ay, XdotH, YdotH);
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-
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-#else
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- float alpha_ggx = roughness * roughness;
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+ float G = V_GGX_anisotropic(ax, ay, dot(T, V), dot(T, L), dot(B, V), dot(B, L), cNdotV, cNdotL);
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+#else // LIGHT_ANISOTROPY_USED
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float D = D_GGX(cNdotH, alpha_ggx);
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- float G = G_GGX_2cos(cNdotL, alpha_ggx) * G_GGX_2cos(cNdotV, alpha_ggx);
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-#endif
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- // F
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+ float G = V_GGX(cNdotL, cNdotV, alpha_ggx);
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+#endif // LIGHT_ANISOTROPY_USED
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+ // F
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float cLdotH5 = SchlickFresnel(cLdotH);
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vec3 F = mix(vec3(cLdotH5), vec3(1.0), f0);
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@@ -263,18 +207,23 @@ void light_compute(vec3 N, vec3 L, vec3 V, float A, vec3 light_color, float atte
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#endif
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#if defined(LIGHT_CLEARCOAT_USED)
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+ // Clearcoat ignores normal_map, use vertex normal instead
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+ float ccNdotL = max(min(A + dot(vertex_normal, L), 1.0), 0.0);
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+ float ccNdotH = clamp(A + dot(vertex_normal, H), 0.0, 1.0);
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+ float ccNdotV = max(dot(vertex_normal, V), 0.0);
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#if !defined(SPECULAR_SCHLICK_GGX)
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float cLdotH5 = SchlickFresnel(cLdotH);
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#endif
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- float Dr = GTR1(cNdotH, mix(.1, .001, clearcoat_gloss));
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+ float Dr = D_GGX(ccNdotH, mix(0.001, 0.1, clearcoat_roughness));
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+ float Gr = 0.25 / (cLdotH * cLdotH);
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float Fr = mix(.04, 1.0, cLdotH5);
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- float Gr = G_GGX_2cos(cNdotL, .25) * G_GGX_2cos(cNdotV, .25);
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-
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- float clearcoat_specular_brdf_NL = 0.25 * clearcoat * Gr * Fr * Dr * cNdotL;
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+ float clearcoat_specular_brdf_NL = clearcoat * Gr * Fr * Dr * cNdotL;
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specular_light += clearcoat_specular_brdf_NL * light_color * attenuation * specular_amount;
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-#endif
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+ // TODO: Clearcoat adds light to the scene right now (it is non-energy conserving), both diffuse and specular need to be scaled by (1.0 - FR)
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+ // but to do so we need to rearrange this entire function
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+#endif // LIGHT_CLEARCOAT_USED
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}
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#ifdef USE_SHADOW_TO_OPACITY
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@@ -587,7 +536,7 @@ void light_process_omni(uint idx, vec3 vertex, vec3 eye_vec, vec3 normal, vec3 v
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float rim, float rim_tint,
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#endif
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#ifdef LIGHT_CLEARCOAT_USED
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- float clearcoat, float clearcoat_gloss,
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+ float clearcoat, float clearcoat_roughness, vec3 vertex_normal,
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#endif
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#ifdef LIGHT_ANISOTROPY_USED
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vec3 binormal, vec3 tangent, float anisotropy,
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@@ -711,7 +660,7 @@ void light_process_omni(uint idx, vec3 vertex, vec3 eye_vec, vec3 normal, vec3 v
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rim * omni_attenuation, rim_tint,
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#endif
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#ifdef LIGHT_CLEARCOAT_USED
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- clearcoat, clearcoat_gloss,
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+ clearcoat, clearcoat_roughness, vertex_normal,
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#endif
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#ifdef LIGHT_ANISOTROPY_USED
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binormal, tangent, anisotropy,
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@@ -827,7 +776,7 @@ void light_process_spot(uint idx, vec3 vertex, vec3 eye_vec, vec3 normal, vec3 v
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float rim, float rim_tint,
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#endif
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#ifdef LIGHT_CLEARCOAT_USED
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- float clearcoat, float clearcoat_gloss,
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+ float clearcoat, float clearcoat_roughness, vec3 vertex_normal,
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#endif
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#ifdef LIGHT_ANISOTROPY_USED
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vec3 binormal, vec3 tangent, float anisotropy,
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@@ -912,7 +861,7 @@ void light_process_spot(uint idx, vec3 vertex, vec3 eye_vec, vec3 normal, vec3 v
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rim * spot_attenuation, rim_tint,
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#endif
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#ifdef LIGHT_CLEARCOAT_USED
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- clearcoat, clearcoat_gloss,
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+ clearcoat, clearcoat_roughness, vertex_normal,
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#endif
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#ifdef LIGHT_ANISOTROPY_USED
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binormal, tangent, anisotropy,
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clayjohn