100 lines
4.0 KiB
HLSL
100 lines
4.0 KiB
HLSL
#ifndef PHYSICALLY_BASED_SKY_RENDERING_HLSL
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#define PHYSICALLY_BASED_SKY_RENDERING_HLSL
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#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
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#include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
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#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Lighting/LightDefinition.cs.hlsl"
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#include "Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl"
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#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Sky/PhysicallyBasedSky/PhysicallyBasedSkyCommon.hlsl"
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#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Sky/SkyUtils.hlsl"
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#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Lighting/AtmosphericScattering/AtmosphericScattering.hlsl"
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#include "Packages/com.unity.render-pipelines.high-definition/Runtime/Lighting/LightLoop/CookieSampling.hlsl"
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float3 _PBRSkyCameraPosPS;
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int _RenderSunDisk;
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float ComputeMoonPhase(CelestialBodyData moon, float3 V)
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{
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float3 M = moon.forward.xyz * moon.distanceFromCamera;
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float radialDistance = moon.distanceFromCamera, rcpRadialDistance = rcp(radialDistance);
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float2 t = IntersectSphere(moon.radius, dot(moon.forward.xyz, -V), radialDistance, rcpRadialDistance);
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float3 N = normalize(M - t.x * V);
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return saturate(-dot(N, moon.sunDirection));
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}
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float ComputeEarthshine(CelestialBodyData moon)
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{
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// Approximate earthshine: sun light reflected from earth
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// cf. A Physically-Based Night Sky Model
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// Compute the percentage of earth surface that is illuminated by the sun as seen from the moon
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//float earthPhase = PI - acos(dot(sun.forward.xyz, -light.forward.xyz));
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//float earthshine = 1.0f - sin(0.5f * earthPhase) * tan(0.5f * earthPhase) * log(rcp(tan(0.25f * earthPhase)));
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// Cheaper approximation of the above (https://www.desmos.com/calculator/11ny6d5j1b)
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float sinPhase = sqrt(max(1 - dot(moon.sunDirection, moon.forward), 0.0f)) * INV_SQRT2;
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float earthshine = 1.0f - sinPhase * sqrt(sinPhase);
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return earthshine * moon.earthshine;
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}
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float3 RenderSunDisk(inout float tFrag, float tExit, float3 V)
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{
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float3 radiance = 0;
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// Intersect and shade emissive celestial bodies.
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// Unfortunately, they don't write depth.
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for (uint i = 0; i < _CelestialBodyCount; i++)
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{
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CelestialBodyData light = _CelestialBodyDatas[i];
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// Celestial body must be outside the atmosphere (request from Pierre D).
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float lightDist = max(light.distanceFromCamera, tExit);
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if (asint(light.angularRadius) != 0 && lightDist < tFrag)
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{
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// We may be able to see the celestial body.
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float3 L = -light.forward.xyz;
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float LdotV = -dot(L, V);
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float radInner = light.angularRadius;
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if (LdotV >= light.flareCosInner) // Sun disk.
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{
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tFrag = lightDist;
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float3 color = light.surfaceColor;
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if (light.type != 0)
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color *= ComputeMoonPhase(light, V) * INV_PI + ComputeEarthshine(light); // Lambertian BRDF
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if (light.surfaceTextureScaleOffset.x > 0)
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{
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float2 proj = float2(dot(V, light.right), dot(V, light.up));
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float2 angles = float2(FastASin(proj.x), FastASin(-proj.y));
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float2 uv = angles * rcp(radInner) * 0.5 + 0.5;
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color *= SampleCookie2D(uv, light.surfaceTextureScaleOffset);
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}
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radiance = color;
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}
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else if (LdotV >= light.flareCosOuter) // Flare region.
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{
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float rad = acos(LdotV);
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float r = max(0, rad - radInner);
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float w = saturate(1 - r * rcp(light.flareSize));
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float3 color = light.flareColor;
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color *= SafePositivePow(w, light.flareFalloff);
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radiance += color;
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}
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}
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}
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return radiance;
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}
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#endif // PHYSICALLY_BASED_SKY_RENDERING_HLSL
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