Shared header file for stochastic reflections

WickedEngine/stochasticSSRHF.hlsli

@@ -0,0 +1,116 @@
+
+#ifndef WI_STOCHASTICSSR_HF
+#define WI_STOCHASTICSSR_HF
+
+// Shared SSR settings:
+static const float SSRMaxRoughness = 1.0f; // Specify max roughness, this can improve performance in complex scenes.
+static const float BRDFBias = 0.7f; 
+
+float ComputeRoughnessMaskScale(in float maxRoughness)
+{
+    float MaxRoughness = clamp(maxRoughness, 0.01f, 1.0f);
+    
+    float roughnessMaskScale = -2.0f / MaxRoughness;
+    return roughnessMaskScale * 1.0f; // 2.0f & 1.0f
+}
+
+float GetRoughnessFade(in float roughness, in float maxRoughness)
+{
+    float roughnessMaskScale = ComputeRoughnessMaskScale(maxRoughness);
+    return min(roughness * roughnessMaskScale + 2, 1.0f);
+}
+
+float GetRoughness(float roughness)
+{
+    return max(roughness, 0.02f);
+}
+
+float Luminance(float3 color)
+{
+    return dot(color, float3(0.2126, 0.7152, 0.0722));
+}
+
+static const float2 offset[9] =
+{
+    float2(-2.0, -2.0),
+    float2(0.0, -2.0),
+    float2(2.0, -2.0),
+    float2(-2.0, 0.0),
+    float2(0.0, 0.0),
+    float2(2.0, 0.0),
+    float2(-2.0, 2.0),
+    float2(0.0, 2.0),
+    float2(2.0, 2.0)
+};
+
+
+uint3 Rand3DPCG16(int3 p)
+{
+    uint3 v = uint3(p);
+
+    v = v * 1664525u + 1013904223u;
+
+    v.x += v.y * v.z;
+    v.y += v.z * v.x;
+    v.z += v.x * v.y;
+    v.x += v.y * v.z;
+    v.y += v.z * v.x;
+    v.z += v.x * v.y;
+
+	// only top 16 bits are well shuffled
+    return v >> 16u;
+}
+
+// Brian Karis, Epic Games "Real Shading in Unreal Engine 4"
+float4 ImportanceSampleGGX(float2 Xi, float Roughness)
+{
+    float m = Roughness * Roughness;
+    float m2 = m * m;
+		
+    float Phi = 2 * PI * Xi.x;
+				 
+    float CosTheta = sqrt((1.0 - Xi.y) / (1.0 + (m2 - 1.0) * Xi.y));
+    float SinTheta = sqrt(max(1e-5, 1.0 - CosTheta * CosTheta));
+				 
+    float3 H;
+    H.x = SinTheta * cos(Phi);
+    H.y = SinTheta * sin(Phi);
+    H.z = CosTheta;
+		
+    float d = (CosTheta * m2 - CosTheta) * CosTheta + 1;
+    float D = m2 / (PI * d * d);
+    float pdf = D * CosTheta;
+
+    return float4(H, pdf);
+}
+
+// [ Duff et al. 2017, "Building an Orthonormal Basis, Revisited" ]
+// http://jcgt.org/published/0006/01/01/
+float3x3 GetTangentBasis(float3 TangentZ)
+{
+    const float Sign = TangentZ.z >= 0 ? 1 : -1;
+    const float a = -rcp(Sign + TangentZ.z);
+    const float b = TangentZ.x * TangentZ.y * a;
+	
+    float3 TangentX = { 1 + Sign * a * pow(TangentZ.x, 2), Sign * b, -Sign * TangentZ.x };
+    float3 TangentY = { b, Sign + a * pow(TangentZ.y, 2), -TangentZ.y };
+
+    return float3x3(TangentX, TangentY, TangentZ);
+}
+
+float3 TangentToWorld(float3 vec, float3 tangentZ)
+{
+    return mul(vec, GetTangentBasis(tangentZ));
+}
+
+float4 TangentToWorld(float4 H, float3 tangentZ)
+{
+    return float4(mul(H.xyz, GetTangentBasis(tangentZ)), H.w);
+}
+
+float3 WorldToTangent(float3 vec, float3 tangentZ)
+{
+    return mul(GetTangentBasis(tangentZ), vec);
+}
+
+#endif // WI_STOCHASTICSSR_HF