Singularity/Library/PackageCache/com.unity.render-pipelines..../ShaderLibrary/CommonLighting.hlsl
2024-05-06 11:45:45 -07:00

501 lines
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HLSL

#ifndef UNITY_COMMON_LIGHTING_INCLUDED
#define UNITY_COMMON_LIGHTING_INCLUDED
#if SHADER_API_MOBILE || SHADER_API_GLES || SHADER_API_GLES3
#pragma warning (disable : 3205) // conversion of larger type to smaller
#endif
// Ligthing convention
// Light direction is oriented backward (-Z). i.e in shader code, light direction is -lightData.forward
//-----------------------------------------------------------------------------
// Helper functions
//-----------------------------------------------------------------------------
// Performs the mapping of the vector 'v' centered within the axis-aligned cube
// of dimensions [-1, 1]^3 to a vector centered within the unit sphere.
// The function expects 'v' to be within the cube (possibly unexpected results otherwise).
// Ref: http://mathproofs.blogspot.com/2005/07/mapping-cube-to-sphere.html
real3 MapCubeToSphere(real3 v)
{
real3 v2 = v * v;
real2 vr3 = v2.xy * rcp(3.0);
return v * sqrt((real3)1.0 - 0.5 * v2.yzx - 0.5 * v2.zxy + vr3.yxx * v2.zzy);
}
// Computes the squared magnitude of the vector computed by MapCubeToSphere().
real ComputeCubeToSphereMapSqMagnitude(real3 v)
{
real3 v2 = v * v;
// Note: dot(v, v) is often computed before this function is called,
// so the compiler should optimize and use the precomputed result here.
return dot(v, v) - v2.x * v2.y - v2.y * v2.z - v2.z * v2.x + v2.x * v2.y * v2.z;
}
// texelArea = 4.0 / (resolution * resolution).
// Ref: http://bpeers.com/blog/?itemid=1017
// This version is less accurate, but much faster than this one:
// http://www.rorydriscoll.com/2012/01/15/cubemap-texel-solid-angle/
real ComputeCubemapTexelSolidAngle(real3 L, real texelArea)
{
// Stretch 'L' by (1/d) so that it points at a side of a [-1, 1]^2 cube.
real d = Max3(abs(L.x), abs(L.y), abs(L.z));
// Since 'L' is a unit vector, we can directly compute its
// new (inverse) length without dividing 'L' by 'd' first.
real invDist = d;
// dw = dA * cosTheta / (dist * dist), cosTheta = 1.0 / dist,
// where 'dA' is the area of the cube map texel.
return texelArea * invDist * invDist * invDist;
}
// Only makes sense for Monte-Carlo integration.
// Normalize by dividing by the total weight (or the number of samples) in the end.
// Integrate[6*(u^2+v^2+1)^(-3/2), {u,-1,1},{v,-1,1}] = 4 * Pi
// Ref: "Stupid Spherical Harmonics Tricks", p. 9.
real ComputeCubemapTexelSolidAngle(real2 uv)
{
real u = uv.x, v = uv.y;
return pow(1 + u * u + v * v, -1.5);
}
real ConvertEvToLuminance(real ev)
{
return exp2(ev - 3.0);
}
real ConvertLuminanceToEv(real luminance)
{
real k = 12.5f;
return log2((luminance * 100.0) / k);
}
//-----------------------------------------------------------------------------
// Attenuation functions
//-----------------------------------------------------------------------------
// Ref: Moving Frostbite to PBR.
// Non physically based hack to limit light influence to attenuationRadius.
// Square the result to smoothen the function.
real DistanceWindowing(real distSquare, real rangeAttenuationScale, real rangeAttenuationBias)
{
// If (range attenuation is enabled)
// rangeAttenuationScale = 1 / r^2
// rangeAttenuationBias = 1
// Else
// rangeAttenuationScale = 2^12 / r^2
// rangeAttenuationBias = 2^24
return saturate(rangeAttenuationBias - Sq(distSquare * rangeAttenuationScale));
}
real SmoothDistanceWindowing(real distSquare, real rangeAttenuationScale, real rangeAttenuationBias)
{
real factor = DistanceWindowing(distSquare, rangeAttenuationScale, rangeAttenuationBias);
return Sq(factor);
}
#define PUNCTUAL_LIGHT_THRESHOLD 0.01 // 1cm (in Unity 1 is 1m)
// Return physically based quadratic attenuation + influence limit to reach 0 at attenuationRadius
real SmoothWindowedDistanceAttenuation(real distSquare, real distRcp, real rangeAttenuationScale, real rangeAttenuationBias)
{
real attenuation = min(distRcp, 1.0 / PUNCTUAL_LIGHT_THRESHOLD);
attenuation *= DistanceWindowing(distSquare, rangeAttenuationScale, rangeAttenuationBias);
// Effectively results in (distRcp)^2 * SmoothDistanceWindowing(...).
return Sq(attenuation);
}
// Square the result to smoothen the function.
real AngleAttenuation(real cosFwd, real lightAngleScale, real lightAngleOffset)
{
return saturate(cosFwd * lightAngleScale + lightAngleOffset);
}
real SmoothAngleAttenuation(real cosFwd, real lightAngleScale, real lightAngleOffset)
{
real attenuation = AngleAttenuation(cosFwd, lightAngleScale, lightAngleOffset);
return Sq(attenuation);
}
// Combines SmoothWindowedDistanceAttenuation() and SmoothAngleAttenuation() in an efficient manner.
// distances = {d, d^2, 1/d, d_proj}, where d_proj = dot(lightToSample, lightData.forward).
real PunctualLightAttenuation(real4 distances, real rangeAttenuationScale, real rangeAttenuationBias,
real lightAngleScale, real lightAngleOffset)
{
real distSq = distances.y;
real distRcp = distances.z;
real distProj = distances.w;
real cosFwd = distProj * distRcp;
real attenuation = min(distRcp, 1.0 / PUNCTUAL_LIGHT_THRESHOLD);
attenuation *= DistanceWindowing(distSq, rangeAttenuationScale, rangeAttenuationBias);
attenuation *= AngleAttenuation(cosFwd, lightAngleScale, lightAngleOffset);
// Effectively results in SmoothWindowedDistanceAttenuation(...) * SmoothAngleAttenuation(...).
return Sq(attenuation);
}
// Applies SmoothDistanceWindowing() after transforming the attenuation ellipsoid into a sphere.
// If r = rsqrt(invSqRadius), then the ellipsoid is defined s.t. r1 = r / invAspectRatio, r2 = r3 = r.
// The transformation is performed along the major axis of the ellipsoid (corresponding to 'r1').
// Both the ellipsoid (e.i. 'axis') and 'unL' should be in the same coordinate system.
// 'unL' should be computed from the center of the ellipsoid.
real EllipsoidalDistanceAttenuation(real3 unL, real3 axis, real invAspectRatio,
real rangeAttenuationScale, real rangeAttenuationBias)
{
// Project the unnormalized light vector onto the axis.
real projL = dot(unL, axis);
// Transform the light vector so that we can work with
// with the ellipsoid as if it was a sphere with the radius of light's range.
real diff = projL - projL * invAspectRatio;
unL -= diff * axis;
real sqDist = dot(unL, unL);
return SmoothDistanceWindowing(sqDist, rangeAttenuationScale, rangeAttenuationBias);
}
// Applies SmoothDistanceWindowing() using the axis-aligned ellipsoid of the given dimensions.
// Both the ellipsoid and 'unL' should be in the same coordinate system.
// 'unL' should be computed from the center of the ellipsoid.
real EllipsoidalDistanceAttenuation(real3 unL, real3 invHalfDim,
real rangeAttenuationScale, real rangeAttenuationBias)
{
// Transform the light vector so that we can work with
// with the ellipsoid as if it was a unit sphere.
unL *= invHalfDim;
real sqDist = dot(unL, unL);
return SmoothDistanceWindowing(sqDist, rangeAttenuationScale, rangeAttenuationBias);
}
// Applies SmoothDistanceWindowing() after mapping the axis-aligned box to a sphere.
// If the diagonal of the box is 'd', invHalfDim = rcp(0.5 * d).
// Both the box and 'unL' should be in the same coordinate system.
// 'unL' should be computed from the center of the box.
real BoxDistanceAttenuation(real3 unL, real3 invHalfDim,
real rangeAttenuationScale, real rangeAttenuationBias)
{
real attenuation = 0.0;
// Transform the light vector so that we can work with
// with the box as if it was a [-1, 1]^2 cube.
unL *= invHalfDim;
// Our algorithm expects the input vector to be within the cube.
if (!(Max3(abs(unL.x), abs(unL.y), abs(unL.z)) > 1.0))
{
real sqDist = ComputeCubeToSphereMapSqMagnitude(unL);
attenuation = SmoothDistanceWindowing(sqDist, rangeAttenuationScale, rangeAttenuationBias);
}
return attenuation;
}
//-----------------------------------------------------------------------------
// IES Helper
//-----------------------------------------------------------------------------
real2 GetIESTextureCoordinate(real3x3 lightToWord, real3 L)
{
// IES need to be sample in light space
real3 dir = mul(lightToWord, -L); // Using matrix on left side do a transpose
// convert to spherical coordinate
real2 sphericalCoord; // .x is theta, .y is phi
// Texture is encoded with cos(phi), scale from -1..1 to 0..1
sphericalCoord.y = (dir.z * 0.5) + 0.5;
real theta = atan2(dir.y, dir.x);
sphericalCoord.x = theta * INV_TWO_PI;
return sphericalCoord;
}
//-----------------------------------------------------------------------------
// Lighting functions
//-----------------------------------------------------------------------------
// Ref: Horizon Occlusion for Normal Mapped Reflections: http://marmosetco.tumblr.com/post/81245981087
real GetHorizonOcclusion(real3 V, real3 normalWS, real3 vertexNormal, real horizonFade)
{
real3 R = reflect(-V, normalWS);
real specularOcclusion = saturate(1.0 + horizonFade * dot(R, vertexNormal));
// smooth it
return specularOcclusion * specularOcclusion;
}
// Ref: Moving Frostbite to PBR - Gotanda siggraph 2011
// Return specular occlusion based on ambient occlusion (usually get from SSAO) and view/roughness info
real GetSpecularOcclusionFromAmbientOcclusion(real NdotV, real ambientOcclusion, real roughness)
{
return saturate(PositivePow(NdotV + ambientOcclusion, exp2(-16.0 * roughness - 1.0)) - 1.0 + ambientOcclusion);
}
// ref: Practical Realtime Strategies for Accurate Indirect Occlusion
// Update ambient occlusion to colored ambient occlusion based on statitics of how light is bouncing in an object and with the albedo of the object
real3 GTAOMultiBounce(real visibility, real3 albedo)
{
real3 a = 2.0404 * albedo - 0.3324;
real3 b = -4.7951 * albedo + 0.6417;
real3 c = 2.7552 * albedo + 0.6903;
real x = visibility;
return max(x, ((x * a + b) * x + c) * x);
}
// Based on Oat and Sander's 2007 technique
// Area/solidAngle of intersection of two cone
real SphericalCapIntersectionSolidArea(real cosC1, real cosC2, real cosB)
{
real r1 = FastACos(cosC1);
real r2 = FastACos(cosC2);
real rd = FastACos(cosB);
real area = 0.0;
if (rd <= max(r1, r2) - min(r1, r2))
{
// One cap is completely inside the other
area = TWO_PI - TWO_PI * max(cosC1, cosC2);
}
else if (rd >= r1 + r2)
{
// No intersection exists
area = 0.0;
}
else
{
real diff = abs(r1 - r2);
real den = r1 + r2 - diff;
real x = 1.0 - saturate((rd - diff) / max(den, 0.0001));
area = smoothstep(0.0, 1.0, x);
area *= TWO_PI - TWO_PI * max(cosC1, cosC2);
}
return area;
}
// ref: Practical Realtime Strategies for Accurate Indirect Occlusion
// http://blog.selfshadow.com/publications/s2016-shading-course/#course_content
// Original Cone-Cone method with cosine weighted assumption (p129 s2016_pbs_activision_occlusion)
real GetSpecularOcclusionFromBentAO_ConeCone(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
{
// Retrieve cone angle
// Ambient occlusion is cosine weighted, thus use following equation. See slide 129
real cosAv = sqrt(1.0 - ambientOcclusion);
roughness = max(roughness, 0.01); // Clamp to 0.01 to avoid edge cases
real cosAs = exp2((-log(10.0) / log(2.0)) * Sq(roughness));
real cosB = dot(bentNormalWS, reflect(-V, normalWS));
return SphericalCapIntersectionSolidArea(cosAv, cosAs, cosB) / (TWO_PI * (1.0 - cosAs));
}
real GetSpecularOcclusionFromBentAO(real3 V, real3 bentNormalWS, real3 normalWS, real ambientOcclusion, real roughness)
{
// Pseudo code:
//SphericalGaussian NDF = WarpedGGXDistribution(normalWS, roughness, V);
//SphericalGaussian Visibility = VisibilityConeSG(bentNormalWS, ambientOcclusion);
//SphericalGaussian UpperHemisphere = UpperHemisphereSG(normalWS);
//return saturate( InnerProduct(NDF, Visibility) / InnerProduct(NDF, UpperHemisphere) );
// 1. Approximate visibility cone with a spherical gaussian of amplitude A=1
// For a cone angle X, we can determine sharpness so that all point inside the cone have a value > Y
// sharpness = (log(Y) - log(A)) / (cos(X) - 1)
// For AO cone, cos(X) = sqrt(1 - ambientOcclusion)
// -> for Y = 0.1, sharpness = -1.0 / (sqrt(1-ao) - 1)
float vs = -1.0f / min(sqrt(1.0f - ambientOcclusion) - 1.0f, -0.001f);
// 2. Approximate upper hemisphere with sharpness = 0.8 and amplitude = 1
float us = 0.8f;
// 3. Compute warped SG Axis of GGX distribution
// Ref: All-Frequency Rendering of Dynamic, Spatially-Varying Reflectance
// https://www.microsoft.com/en-us/research/wp-content/uploads/2009/12/sg.pdf
float NoV = dot(V, normalWS);
float3 NDFAxis = (2 * NoV * normalWS - V) * (0.5f / max(roughness * roughness * NoV, 0.001f));
float umLength1 = length(NDFAxis + vs * bentNormalWS);
float umLength2 = length(NDFAxis + us * normalWS);
float d1 = 1 - exp(-2 * umLength1);
float d2 = 1 - exp(-2 * umLength2);
float expFactor1 = exp(umLength1 - umLength2 + us - vs);
return saturate(expFactor1 * (d1 * umLength2) / (d2 * umLength1));
}
// Ref: Steve McAuley - Energy-Conserving Wrapped Diffuse
real ComputeWrappedDiffuseLighting(real NdotL, real w)
{
return saturate((NdotL + w) / ((1.0 + w) * (1.0 + w)));
}
// Jimenez variant for eye
real ComputeWrappedPowerDiffuseLighting(real NdotL, real w, real p)
{
return pow(saturate((NdotL + w) / (1.0 + w)), p) * (p + 1) / (w * 2.0 + 2.0);
}
// Ref: The Technical Art of Uncharted 4 - Brinck and Maximov 2016
real ComputeMicroShadowing(real AO, real NdotL, real opacity)
{
real aperture = 2.0 * AO * AO;
real microshadow = saturate(NdotL + aperture - 1.0);
return lerp(1.0, microshadow, opacity);
}
real3 ComputeShadowColor(real shadow, real3 shadowTint, real penumbraFlag)
{
// The origin expression is
// lerp(real3(1.0, 1.0, 1.0) - ((1.0 - shadow) * (real3(1.0, 1.0, 1.0) - shadowTint))
// , shadow * lerp(shadowTint, lerp(shadowTint, real3(1.0, 1.0, 1.0), shadow), shadow)
// , penumbraFlag);
// it has been simplified to this
real3 invTint = real3(1.0, 1.0, 1.0) - shadowTint;
real shadow3 = shadow * shadow * shadow;
return lerp(real3(1.0, 1.0, 1.0) - ((1.0 - shadow) * invTint)
, shadow3 * invTint + shadow * shadowTint,
penumbraFlag);
}
// This is the same method as the one above. Simply the shadow is a real3 to support colored shadows.
real3 ComputeShadowColor(real3 shadow, real3 shadowTint, real penumbraFlag)
{
// The origin expression is
// lerp(real3(1.0, 1.0, 1.0) - ((1.0 - shadow) * (real3(1.0, 1.0, 1.0) - shadowTint))
// , shadow * lerp(shadowTint, lerp(shadowTint, real3(1.0, 1.0, 1.0), shadow), shadow)
// , penumbraFlag);
// it has been simplified to this
real3 invTint = real3(1.0, 1.0, 1.0) - shadowTint;
real3 shadow3 = shadow * shadow * shadow;
return lerp(real3(1.0, 1.0, 1.0) - ((1.0 - shadow) * invTint)
, shadow3 * invTint + shadow * shadowTint,
penumbraFlag);
}
//-----------------------------------------------------------------------------
// Helper functions
//--------------------------------------------------------------------------- --
// Ref: "Crafting a Next-Gen Material Pipeline for The Order: 1886".
real ClampNdotV(real NdotV)
{
return max(NdotV, 0.0001); // Approximately 0.0057 degree bias
}
// Helper function to return a set of common angle used when evaluating BSDF
// NdotL and NdotV are unclamped
void GetBSDFAngle(real3 V, real3 L, real NdotL, real NdotV,
out real LdotV, out real NdotH, out real LdotH, out real invLenLV)
{
// Optimized math. Ref: PBR Diffuse Lighting for GGX + Smith Microsurfaces (slide 114), assuming |L|=1 and |V|=1
LdotV = dot(L, V);
invLenLV = rsqrt(max(2.0 * LdotV + 2.0, FLT_EPS)); // invLenLV = rcp(length(L + V)), clamp to avoid rsqrt(0) = inf, inf * 0 = NaN
NdotH = saturate((NdotL + NdotV) * invLenLV);
LdotH = saturate(invLenLV * LdotV + invLenLV);
}
// Inputs: normalized normal and view vectors.
// Outputs: front-facing normal, and the new non-negative value of the cosine of the view angle.
// Important: call Orthonormalize() on the tangent and recompute the bitangent afterwards.
real3 GetViewReflectedNormal(real3 N, real3 V, out real NdotV)
{
// Fragments of front-facing geometry can have back-facing normals due to interpolation,
// normal mapping and decals. This can cause visible artifacts from both direct (negative or
// extremely high values) and indirect (incorrect lookup direction) lighting.
// There are several ways to avoid this problem. To list a few:
//
// 1. Setting { NdotV = max(<N,V>, SMALL_VALUE) }. This effectively removes normal mapping
// from the affected fragments, making the surface appear flat.
//
// 2. Setting { NdotV = abs(<N,V>) }. This effectively reverses the convexity of the surface.
// It also reduces light leaking from non-shadow-casting lights. Note that 'NdotV' can still
// be 0 in this case.
//
// It's important to understand that simply changing the value of the cosine is insufficient.
// For one, it does not solve the incorrect lookup direction problem, since the normal itself
// is not modified. There is a more insidious issue, however. 'NdotV' is a constituent element
// of the mathematical system describing the relationships between different vectors - and
// not just normal and view vectors, but also light vectors, half vectors, tangent vectors, etc.
// Changing only one angle (or its cosine) leaves the system in an inconsistent state, where
// certain relationships can take on different values depending on whether 'NdotV' is used
// in the calculation or not. Therefore, it is important to change the normal (or another
// vector) in order to leave the system in a consistent state.
//
// We choose to follow the conceptual approach (2) by reflecting the normal around the
// (<N,V> = 0) boundary if necessary, as it allows us to preserve some normal mapping details.
NdotV = dot(N, V);
// N = (NdotV >= 0.0) ? N : (N - 2.0 * NdotV * V);
N += (2.0 * saturate(-NdotV)) * V;
NdotV = abs(NdotV);
return N;
}
// Generates an orthonormal (row-major) basis from a unit vector. TODO: make it column-major.
// The resulting rotation matrix has the determinant of +1.
// Ref: 'ortho_basis_pixar_r2' from http://marc-b-reynolds.github.io/quaternions/2016/07/06/Orthonormal.html
real3x3 GetLocalFrame(real3 localZ)
{
real x = localZ.x;
real y = localZ.y;
real z = localZ.z;
real sz = FastSign(z);
real a = 1 / (sz + z);
real ya = y * a;
real b = x * ya;
real c = x * sz;
real3 localX = real3(c * x * a - 1, sz * b, c);
real3 localY = real3(b, y * ya - sz, y);
// Note: due to the quaternion formulation, the generated frame is rotated by 180 degrees,
// s.t. if localZ = {0, 0, 1}, then localX = {-1, 0, 0} and localY = {0, -1, 0}.
return real3x3(localX, localY, localZ);
}
// Generates an orthonormal (row-major) basis from a unit vector. TODO: make it column-major.
// The resulting rotation matrix has the determinant of +1.
real3x3 GetLocalFrame(real3 localZ, real3 localX)
{
real3 localY = cross(localZ, localX);
return real3x3(localX, localY, localZ);
}
// Construct a right-handed view-dependent orthogonal basis around the normal:
// b0-b2 is the view-normal aka reflection plane.
real3x3 GetOrthoBasisViewNormal(real3 V, real3 N, real unclampedNdotV, bool testSingularity = false)
{
real3x3 orthoBasisViewNormal;
if (testSingularity && (abs(1.0 - unclampedNdotV) <= FLT_EPS))
{
// In this case N == V, and azimuth orientation around N shouldn't matter for the caller,
// we can use any quaternion-based method, like Frisvad or Reynold's (Pixar):
orthoBasisViewNormal = GetLocalFrame(N);
}
else
{
orthoBasisViewNormal[0] = normalize(V - N * unclampedNdotV);
orthoBasisViewNormal[2] = N;
orthoBasisViewNormal[1] = cross(orthoBasisViewNormal[2], orthoBasisViewNormal[0]);
}
return orthoBasisViewNormal;
}
// Move this here since it's used by both LightLoop.hlsl and RaytracingLightLoop.hlsl
bool IsMatchingLightLayer(uint lightLayers, uint renderingLayers)
{
return (lightLayers & renderingLayers) != 0;
}
#if SHADER_API_MOBILE || SHADER_API_GLES || SHADER_API_GLES3
#pragma warning (enable : 3205) // conversion of larger type to smaller
#endif
#endif // UNITY_COMMON_LIGHTING_INCLUDED