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#ifndef SPRITE_SPECULAR_INCLUDED
#define SPRITE_SPECULAR_INCLUDED
#include "ShaderMaths.cginc"
////////////////////////////////////////
// Specular functions
//
#if defined(_SPECULAR) || defined(_SPECULAR_GLOSSMAP)
#define SPECULAR
//ALL THESE FUNCTIONS ARE TAKEN AND ADAPTED FROM UNITY'S OWN PHYSICS BASED STANDARD SHADER
uniform float _Metallic;
uniform float _Glossiness;
uniform float _GlossMapScale;
uniform sampler2D _MetallicGlossMap;
struct SpecularLightData
{
half3 lighting;
half3 specular;
};
struct SpecularCommonData
{
half3 diffColor, specColor;
// Note: smoothness & oneMinusReflectivity for optimization purposes, mostly for DX9 SM2.0 level.
// Most of the math is being done on these (1-x) values, and that saves a few precious ALU slots.
half oneMinusReflectivity, smoothness;
half alpha;
};
inline half2 getMetallicGloss(float2 uv)
{
half2 mg;
#ifdef _SPECULAR_GLOSSMAP
mg = tex2D(_MetallicGlossMap, uv).ra;
mg.g *= _GlossMapScale;
#else
mg.r = _Metallic;
mg.g = _Glossiness;
#endif
return mg;
}
inline half getOneMinusReflectivityFromMetallic(half metallic)
{
// We'll need oneMinusReflectivity, so
// 1-reflectivity = 1-lerp(dielectricSpec, 1, metallic) = lerp(1-dielectricSpec, 0, metallic)
// store (1-dielectricSpec) in unity_ColorSpaceDielectricSpec.a, then
// 1-reflectivity = lerp(alpha, 0, metallic) = alpha + metallic*(0 - alpha) =
// = alpha - metallic * alpha
half oneMinusDielectricSpec = unity_ColorSpaceDielectricSpec.a;
return oneMinusDielectricSpec - metallic * oneMinusDielectricSpec;
}
inline SpecularCommonData getSpecularData(float2 uv, half4 texureColor, fixed4 color)
{
half2 metallicGloss = getMetallicGloss(uv);
half metallic = metallicGloss.x;
half smoothness = metallicGloss.y; // this is 1 minus the square root of real roughness m.
fixed4 albedo = calculatePixel(texureColor, color);
half3 specColor = lerp (unity_ColorSpaceDielectricSpec.rgb, albedo, metallic);
half oneMinusReflectivity = getOneMinusReflectivityFromMetallic(metallic);
half3 diffColor = albedo * oneMinusReflectivity;
SpecularCommonData o = (SpecularCommonData)0;
o.diffColor = diffColor;
o.specColor = specColor;
o.oneMinusReflectivity = oneMinusReflectivity;
o.smoothness = smoothness;
#if defined(_ALPHAPREMULTIPLY_ON) && (SHADER_TARGET >= 30)
// Reflectivity 'removes' from the rest of components, including Transparency
// outAlpha = 1-(1-alpha)*(1-reflectivity) = 1-(oneMinusReflectivity - alpha*oneMinusReflectivity) =
// = 1-oneMinusReflectivity + alpha*oneMinusReflectivity
//o.alpha = 1-oneMinusReflectivity + albedo.a*oneMinusReflectivity;
o.alpha = albedo.a;
#else
o.alpha = albedo.a;
#endif
return o;
}
inline half SmoothnessToPerceptualRoughness(half smoothness)
{
return (1 - smoothness);
}
inline half PerceptualRoughnessToRoughness(half perceptualRoughness)
{
return perceptualRoughness * perceptualRoughness;
}
// Ref: http://jcgt.org/published/0003/02/03/paper.pdf
inline half SmithJointGGXVisibilityTerm (half NdotL, half NdotV, half roughness)
{
#if 0
// Original formulation:
// lambda_v = (-1 + sqrt(a2 * (1 - NdotL2) / NdotL2 + 1)) * 0.5f;
// lambda_l = (-1 + sqrt(a2 * (1 - NdotV2) / NdotV2 + 1)) * 0.5f;
// G = 1 / (1 + lambda_v + lambda_l);
// Reorder code to be more optimal
half a = roughness;
half a2 = a * a;
half lambdaV = NdotL * sqrt((-NdotV * a2 + NdotV) * NdotV + a2);
half lambdaL = NdotV * sqrt((-NdotL * a2 + NdotL) * NdotL + a2);
// Simplify visibility term: (2.0f * NdotL * NdotV) / ((4.0f * NdotL * NdotV) * (lambda_v + lambda_l + 1e-5f));
return 0.5f / (lambdaV + lambdaL + 1e-5f); // This function is not intended to be running on Mobile,
// therefore epsilon is smaller than can be represented by half
#else
// Approximation of the above formulation (simplify the sqrt, not mathematically correct but close enough)
half a = roughness;
half lambdaV = NdotL * (NdotV * (1 - a) + a);
half lambdaL = NdotV * (NdotL * (1 - a) + a);
return 0.5f / (lambdaV + lambdaL + 1e-5f);
#endif
}
inline half GGXTerm (half NdotH, half roughness)
{
half a2 = roughness * roughness;
half d = (NdotH * a2 - NdotH) * NdotH + 1.0f; // 2 mad
return UNITY_INV_PI * a2 / (d * d + 1e-7f); // This function is not intended to be running on Mobile,
// therefore epsilon is smaller than what can be represented by half
}
inline half3 FresnelTerm (half3 F0, half cosA)
{
half t = pow5 (1 - cosA); // ala Schlick interpoliation
return F0 + (1-F0) * t;
}
inline half3 FresnelLerp (half3 F0, half F90, half cosA)
{
half t = pow5 (1 - cosA); // ala Schlick interpoliation
return lerp (F0, F90, t);
}
// Note: Disney diffuse must be multiply by diffuseAlbedo / PI. This is done outside of this function.
inline half DisneyDiffuse(half NdotV, half NdotL, half LdotH, half perceptualRoughness)
{
half fd90 = 0.5 + 2 * LdotH * LdotH * perceptualRoughness;
// Two schlick fresnel term
half lightScatter = (1 + (fd90 - 1) * pow5(1 - NdotL));
half viewScatter = (1 + (fd90 - 1) * pow5(1 - NdotV));
return lightScatter * viewScatter;
}
// Main Physically Based BRDF
// Derived from Disney work and based on Torrance-Sparrow micro-facet model
//
// BRDF = kD / pi + kS * (D * V * F) / 4
// I = BRDF * NdotL
//
// * NDF (depending on UNITY_BRDF_GGX):
// a) Normalized BlinnPhong
// b) GGX
// * Smith for Visiblity term
// * Schlick approximation for Fresnel
SpecularLightData calculatePhysicsBasedSpecularLight(half3 specColor, half oneMinusReflectivity, half smoothness, half3 normal, half3 viewDir, half3 lightdir, half3 lightColor, half3 indirectDiffuse, half3 indirectSpecular)
{
half perceptualRoughness = SmoothnessToPerceptualRoughness (smoothness);
half3 halfDir = safeNormalize (lightdir + viewDir);
// NdotV should not be negative for visible pixels, but it can happen due to perspective projection and normal mapping
// In this case normal should be modified to become valid (i.e facing camera) and not cause weird artifacts.
// but this operation adds few ALU and users may not want it. Alternative is to simply take the abs of NdotV (less correct but works too).
// Following define allow to control this. Set it to 0 if ALU is critical on your platform.
// This correction is interesting for GGX with SmithJoint visibility function because artifacts are more visible in this case due to highlight edge of rough surface
// Edit: Disable this code by default for now as it is not compatible with two sided lighting used in SpeedTree.
#define UNITY_HANDLE_CORRECTLY_NEGATIVE_NDOTV 0
#if UNITY_HANDLE_CORRECTLY_NEGATIVE_NDOTV
// The amount we shift the normal toward the view vector is defined by the dot product.
half shiftAmount = dot(normal, viewDir);
normal = shiftAmount < 0.0f ? normal + viewDir * (-shiftAmount + 1e-5f) : normal;
// A re-normalization should be applied here but as the shift is small we don't do it to save ALU.
//normal = normalize(normal);
half nv = saturate(dot(normal, viewDir)); // TODO: this saturate should no be necessary here
#else
half nv = abs(dot(normal, viewDir)); // This abs allow to limit artifact
#endif
half nl = saturate(dot(normal, lightdir));
half nh = saturate(dot(normal, halfDir));
half lv = saturate(dot(lightdir, viewDir));
half lh = saturate(dot(lightdir, halfDir));
// Diffuse term
half diffuseTerm = DisneyDiffuse(nv, nl, lh, perceptualRoughness) * nl;
// Specular term
// HACK: theoretically we should divide diffuseTerm by Pi and not multiply specularTerm!
// BUT 1) that will make shader look significantly darker than Legacy ones
// and 2) on engine side "Non-important" lights have to be divided by Pi too in cases when they are injected into ambient SH
half roughness = PerceptualRoughnessToRoughness(perceptualRoughness);
half V = SmithJointGGXVisibilityTerm (nl, nv, roughness);
half D = GGXTerm (nh, roughness);
half specularTerm = V*D * UNITY_PI; // Torrance-Sparrow model, Fresnel is applied later
# ifdef UNITY_COLORSPACE_GAMMA
specularTerm = sqrt(max(1e-4h, specularTerm));
# endif
// specularTerm * nl can be NaN on Metal in some cases, use max() to make sure it's a sane value
specularTerm = max(0, specularTerm * nl);
// surfaceReduction = Int D(NdotH) * NdotH * Id(NdotL>0) dH = 1/(roughness^2+1)
half surfaceReduction;
# ifdef UNITY_COLORSPACE_GAMMA
surfaceReduction = 1.0 - 0.28f * roughness * perceptualRoughness; // 1-0.28*x^3 as approximation for (1/(x^4+1))^(1/2.2) on the domain [0;1]
# else
surfaceReduction = 1.0 / (roughness*roughness + 1.0); // fade \in [0.5;1]
# endif
// To provide true Lambert lighting, we need to be able to kill specular completely.
specularTerm *= any(specColor) ? 1.0 : 0.0;
half grazingTerm = saturate(smoothness + (1-oneMinusReflectivity));
SpecularLightData outData = (SpecularLightData)0;
outData.lighting = indirectDiffuse + lightColor * diffuseTerm;
outData.specular = (specularTerm * lightColor * FresnelTerm (specColor, lh)) + (surfaceReduction * indirectSpecular * FresnelLerp (specColor, grazingTerm, nv));
return outData;
}
#endif // _SPECULAR && _SPECULAR_GLOSSMAP
#endif // SPRITE_SPECULAR_INCLUDED