Add code

Implement basic diffuse and specular BRDF based heavily on silent's
filamented shader.

1 files changed, 393 insertions, 0 deletions

diff --git a/filamented.cginc b/filamented.cginc
new file mode 100644
index 0000000..2b1e876
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+++ b/filamented.cginc
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+#ifndef __FILAMENTED_INC
+#define __FILAMENTED_INC
+
+#include "UnityImageBasedLighting.cginc"
+#include "UnityStandardUtils.cginc"
+
+#include "math.cginc"
+
+// I made changes to this code.
+
+/*
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+Unity Built-in Shaders   
+
+Copyright (c) 2016 Unity Technologies
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
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+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
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+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+#define MIN_PERCEPTUAL_ROUGHNESS 0.045
+
+UNITY_DECLARE_TEX2D_FLOAT(_DFG);
+
+float3 PrefilteredDFG_LUT(float lod, float NoV) {
+	return UNITY_SAMPLE_TEX2D(_DFG, float2(NoV, lod));
+}
+
+float3 specularDFG(const float3 dfg, const float f0) {
+	return lerp(dfg.xxx, dfg.yyy, f0);
+}
+
+float D_GGX(float roughness, float NoH, const float3 h) {
+	// Walter et al. 2007, "Microfacet Models for Refraction through Rough Surfaces"
+
+	// In mediump, there are two problems computing 1.0 - NoH^2
+	// 1) 1.0 - NoH^2 suffers floating point cancellation when NoH^2 is close to 1 (highlights)
+	// 2) NoH doesn't have enough precision around 1.0
+	// Both problem can be fixed by computing 1-NoH^2 in highp and providing NoH in highp as well
+
+	// However, we can do better using Lagrange's identity:
+	//      ||a x b||^2 = ||a||^2 ||b||^2 - (a . b)^2
+	// since N and H are unit vectors: ||N x H||^2 = 1.0 - NoH^2
+	// This computes 1.0 - NoH^2 directly (which is close to zero in the highlights and has
+	// enough precision).
+	// Overall this yields better performance, keeping all computations in mediump
+	// Not available without reworking to pass NxH to the function
+	float oneMinusNoHSquared = 1.0 - NoH * NoH;
+	float a = NoH * roughness;
+	float k = roughness / (oneMinusNoHSquared + a * a);
+	float d = k * k * (1.0 / PI);
+	return d;
+}
+
+float F_Schlick(float f0, float VoH) {
+	return f0 + (1.0 - f0) * pow5(1.0 - VoH);
+}
+
+float V_SmithGGXCorrelated(float roughness, float NoV, float NoL) {
+	// Heitz 2014, "Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs"
+	float a2 = roughness * roughness;
+	float lambdaV = NoL * sqrt((NoV - a2 * NoV) * NoV + a2);
+	float lambdaL = NoV * sqrt((NoL - a2 * NoL) * NoL + a2);
+	float v = 0.5 / (lambdaV + lambdaL);
+	return v;
+}
+
+float V_SmithGGXCorrelated_Fast(float roughness, float NoV, float NoL) {
+    // Hammon 2017, "PBR Diffuse Lighting for GGX+Smith Microsurfaces"
+    float v = 0.5 / lerp(2.0 * NoL * NoV, NoL + NoV, roughness);
+    return v;
+}
+
+float perceptualRoughnessToRoughness(float perceptualRoughness) {
+    return perceptualRoughness * perceptualRoughness;
+}
+
+float roughnessToPerceptualRoughness(float roughness) {
+    return sqrt(roughness);
+}
+
+float normalFiltering(float perceptualRoughness, const float3 worldNormal) {
+    // Kaplanyan 2016, "Stable specular highlights"
+    // Tokuyoshi 2017, "Error Reduction and Simplification for Shading Anti-Aliasing"
+    // Tokuyoshi and Kaplanyan 2019, "Improved Geometric Specular Antialiasing"
+
+    // This implementation is meant for deferred rendering in the original paper but
+    // we use it in forward rendering as well (as discussed in Tokuyoshi and Kaplanyan
+    // 2019). The main reason is that the forward version requires an expensive transform
+    // of the half vector by the tangent frame for every light. This is therefore an
+    // approximation but it works well enough for our needs and provides an improvement
+    // over our original implementation based on Vlachos 2015, "Advanced VR Rendering".
+
+    float3 du = ddx(worldNormal);
+    float3 dv = ddy(worldNormal);
+
+    float variance = _specularAntiAliasingVariance * (dot(du, du) + dot(dv, dv));
+
+    float roughness = perceptualRoughnessToRoughness(perceptualRoughness);
+    float kernelRoughness = min(2.0 * variance, _specularAntiAliasingThreshold);
+    float squareRoughness = saturate(roughness * roughness + kernelRoughness);
+
+    return roughnessToPerceptualRoughness(sqrt(squareRoughness));
+}
+
+float3 energyCompensation(float3 dfg, float3 f0)
+{
+  // Energy compensation for multiple scattering in a microfacet model
+  // See "Multiple-Scattering Microfacet BSDFs with the Smith Model"
+  return 1.0 + f0 * (1.0 / dfg.yyy - 1.0);
+}
+
+half3 Unity_GlossyEnvironment_local (UNITY_ARGS_TEXCUBE(tex), half4 hdr, Unity_GlossyEnvironmentData glossIn)
+{
+	half perceptualRoughness = glossIn.roughness /* perceptualRoughness */ ;
+
+	// Workaround for issue where objects are blurrier than they should be
+	// due to specular AA.
+	float roughnessAdjustment = 1-perceptualRoughness;
+	roughnessAdjustment = MIN_PERCEPTUAL_ROUGHNESS * roughnessAdjustment * roughnessAdjustment;
+	perceptualRoughness = perceptualRoughness - roughnessAdjustment;
+
+	// Unity derivation
+	perceptualRoughness = perceptualRoughness*(1.7 - 0.7 * perceptualRoughness);
+	// Filament derivation
+	// perceptualRoughness = perceptualRoughness * (2.0 - perceptualRoughness);
+	half mip = perceptualRoughnessToMipmapLevel(perceptualRoughness);
+	half3 R = glossIn.reflUVW;
+	half4 rgbm = UNITY_SAMPLE_TEXCUBE_LOD(tex, R, mip);
+
+	return DecodeHDR(rgbm, hdr);
+}
+
+inline half3 UnityGI_prefilteredRadiance(const UnityGIInput data,
+    const float perceptualRoughness, const float3 r) {
+  half3 specular;
+
+  Unity_GlossyEnvironmentData glossIn = (Unity_GlossyEnvironmentData)0;
+  glossIn.roughness = perceptualRoughness;
+  glossIn.reflUVW = r;
+
+#ifdef UNITY_SPECCUBE_BOX_PROJECTION
+  // we will tweak reflUVW in glossIn directly (as we pass it to Unity_GlossyEnvironment twice for probe0 and pr            obe1), so keep original to pass into BoxProjectedCubemapDirection
+	half3 originalReflUVW = glossIn.reflUVW;
+	glossIn.reflUVW = BoxProjectedCubemapDirection(originalReflUVW,
+			data.worldPos, data.probePosition[0], data.boxMin[0], data.boxMax[0]);
+#endif
+
+#ifdef _GLOSSYREFLECTIONS_OFF
+    specular = unity_IndirectSpecColor.rgb;
+#else
+  half3 env0 = Unity_GlossyEnvironment_local (UNITY_PASS_TEXCUBE(unity_SpecCube0), data.probeHDR[0], glossIn);
+#ifdef UNITY_SPECCUBE_BLENDING
+  const float kBlendFactor = 0.99999;
+  float blendLerp = data.boxMin[0].w;
+  UNITY_BRANCH
+    if (blendLerp < kBlendFactor)
+    {
+#ifdef UNITY_SPECCUBE_BOX_PROJECTION
+      glossIn.reflUVW = BoxProjectedCubemapDirection (originalReflUVW, data.worldPos, data.probePosition                        [1], data.boxMin[1], data.boxMax[1]);
+#endif  // UNITY_SPECCUBE_BOX_PROJECTION
+
+      half3 env1 = Unity_GlossyEnvironment_local (UNITY_PASS_TEXCUBE_SAMPLER(unity_SpecCube1,unity_SpecCube0                    ), data.probeHDR[1], glossIn);
+      specular = lerp(env1, env0, blendLerp);                                                                           }
+    else
+    {
+      specular = env0;
+    }
+#else
+  specular = env0;
+#endif  // UNITY_SPECCUBE_BLENDING
+#endif  // _GLOSSYREFLECTIONS_OFF
+
+  return specular;
+}
+
+#endif
+