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@@ -150,10 +150,10 @@ ANKI_RP Vec3 specularIsotropicLobe(GbufferInfo gbuffer, Vec3 viewDir, Vec3 frag2
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return F * (V * D);
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}
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-Vec3 envBRDF(Vec3 specular, F32 roughness, texture2D integrationLut, sampler integrationLutSampler, F32 NoV)
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+Vec3 specularDFG(Vec3 F0, F32 roughness, texture2D integrationLut, sampler integrationLutSampler, F32 NoV)
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{
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const Vec2 envBRDF = textureLod(integrationLut, integrationLutSampler, Vec2(roughness, NoV), 0.0).xy;
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- return specular * envBRDF.x + min(1.0, 50.0 * specular.g) * envBRDF.y;
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+ return mix(envBRDF.xxx, envBRDF.yyy, F0);
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}
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ANKI_RP F32 computeSpotFactor(ANKI_RP Vec3 l, ANKI_RP F32 outerCos, ANKI_RP F32 innerCos, ANKI_RP Vec3 spotDir)
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@@ -399,3 +399,56 @@ U32 computeShadowCascadeIndex(F32 distance, F32 p, F32 effectiveShadowDistance,
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idx = min(idx, shadowCascadeCountf - 1.0f);
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return U32(idx);
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}
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+
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+/// To play with it use https://www.shadertoy.com/view/sttSDf
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+/// http://jcgt.org/published/0007/04/01/paper.pdf by Eric Heitz
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+/// Input v: view direction
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+/// Input alphaX, alphaY: roughness parameters
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+/// Input u1, u2: uniform random numbers
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+/// Output: normal sampled with PDF D_Ve(nE) = G1(v) * max(0, dot(v, nE)) * D(nE) / v.z
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+Vec3 sampleGgxVndf(Vec3 v, F32 alphaX, F32 alphaY, F32 u1, F32 u2)
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+{
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+ // Section 3.2: transforming the view direction to the hemisphere configuration
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+ const Vec3 vH = normalize(Vec3(alphaX * v.x, alphaY * v.y, v.z));
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+
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+ // Section 4.1: orthonormal basis (with special case if cross product is zero)
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+ const F32 lensq = vH.x * vH.x + vH.y * vH.y;
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+ const Vec3 tangent1 = (lensq > 0.0) ? Vec3(-vH.y, vH.x, 0) * inversesqrt(lensq) : Vec3(1.0, 0.0, 0.0);
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+ const Vec3 tangent2 = cross(vH, tangent1);
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+
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+ // Section 4.2: parameterization of the projected area
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+ const F32 r = sqrt(u1);
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+ const F32 phi = 2.0 * PI * u2;
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+ const F32 t1 = r * cos(phi);
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+ F32 t2 = r * sin(phi);
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+ const F32 s = 0.5 * (1.0 + vH.z);
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+ t2 = (1.0 - s) * sqrt(1.0 - t1 * t1) + s * t2;
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+
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+ // Section 4.3: reprojection onto hemisphere
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+ const Vec3 nH = t1 * tangent1 + t2 * tangent2 + sqrt(max(0.0, 1.0 - t1 * t1 - t2 * t2)) * vH;
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+
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+ // Section 3.4: transforming the normal back to the ellipsoid configuration
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+ const Vec3 nE = normalize(Vec3(alphaX * nH.x, alphaY * nH.y, max(0.0, nH.z)));
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+
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+ return nE;
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+}
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+
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+/// Calculate the reflection vector based on roughness.
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+Vec3 sampleReflectionVector(Vec3 viewDir, Vec3 normal, F32 roughness, Vec2 uniformRandom)
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+{
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+ const Mat3 tbn = rotationFromDirection(normal);
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+ const Mat3 tbnT = transpose(tbn);
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+ const Vec3 viewDirTbn = tbnT * (-viewDir);
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+
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+ Vec3 sampledNormalTbn = sampleGgxVndf(viewDirTbn, roughness, roughness, uniformRandom.x, uniformRandom.y);
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+ const Bool perfectReflection = false; // For debugging
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+ if(perfectReflection)
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+ {
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+ sampledNormalTbn = Vec3(0.0, 0.0, 1.0);
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+ }
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+
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+ const Vec3 reflectedDirTbn = reflect(-viewDirTbn, sampledNormalTbn);
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+
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+ // Transform reflected_direction back to the initial space.
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+ return tbn * reflectedDirTbn;
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+}
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Panagiotis Christopoulos Charitos
