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76 行
2.8 KiB
76 行
2.8 KiB
#ifndef LIGHTWEIGHT_BRDF_INCLUDED
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#define LIGHTWEIGHT_BRDF_INCLUDED
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#define PI 3.14159265359f
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half MetallicSetup_Reflectivity()
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{
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return 1.0h - OneMinusReflectivityFromMetallic(_Metallic);
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}
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half3 LightweightBRDFDirect(half3 diffColor, half3 specColor, half smoothness, half RdotL)
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{
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#ifndef _SPECULARHIGHLIGHTS_OFF
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half RdotLPow4 = Pow4(RdotL);
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half LUT_RANGE = 16.0; // must match range in NHxRoughness() function in GeneratedTextures.cpp
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// Lookup texture to save instructions
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half perceptualRoughness = 1.0 - smoothness;
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half specular = tex2D(unity_NHxRoughness, half2(RdotLPow4, perceptualRoughness)).UNITY_ATTEN_CHANNEL * LUT_RANGE;
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return diffColor + specular * specColor;
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#else
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return diffColor;
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#endif
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}
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// Based on Minimalist CookTorrance BRDF
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// Implementation is slightly different from original derivation: http://www.thetenthplanet.de/archives/255
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//
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// * NDF [Modified] GGX
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// * Modified Kelemen and Szirmay-Kalos for Visibility term
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// * Fresnel approximated with 1/LdotH
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half3 LightweightBDRF(half3 diffColor, half3 specColor, half oneMinusReflectivity, half perceptualRoughness, half3 normal, half3 lightDirection, half3 viewDir)
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{
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#ifndef _SPECULARHIGHLIGHTS_OFF
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half3 halfDir = Unity_SafeNormalize(lightDirection + viewDir);
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half NoH = saturate(dot(normal, halfDir));
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half LoH = saturate(dot(lightDirection, halfDir));
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// Specular term
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half roughness = perceptualRoughness * perceptualRoughness;
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// GGX Distribution multiplied by combined approximation of Visibility and Fresnel
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// See "Optimizing PBR for Mobile" from Siggraph 2015 moving mobile graphics course
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// https://community.arm.com/events/1155
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half a2 = roughness * roughness;
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half d = NoH * NoH * (a2 - 1.h) + 1.00001h;
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half LoH2 = LoH * LoH;
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half specularTerm = a2 / ((d * d) * max(0.1h, LoH2) * (roughness + 0.5h) * 4);
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// on mobiles (where half actually means something) denominator have risk of overflow
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// clamp below was added specifically to "fix" that, but dx compiler (we convert bytecode to metal/gles)
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// sees that specularTerm have only non-negative terms, so it skips max(0,..) in clamp (leaving only min(100,...))
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#if defined (SHADER_API_MOBILE)
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specularTerm = specularTerm - 1e-4h;
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#endif
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#if defined (SHADER_API_MOBILE)
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specularTerm = clamp(specularTerm, 0.0, 100.0); // Prevent FP16 overflow on mobiles
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#endif
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return diffColor + specularTerm * specColor;
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#else
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return diffColor;
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#endif
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}
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half3 LightweightBRDFIndirect(half3 diffColor, half3 specColor, UnityIndirect indirect, float roughness, half grazingTerm, half fresnelTerm)
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{
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half3 c = indirect.diffuse * diffColor;
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float surfaceReduction = 1.0 / (roughness * roughness + 1.0);
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c += surfaceReduction * indirect.specular * lerp(specColor, grazingTerm, fresnelTerm);
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return c;
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}
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#endif
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