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141 行
5.6 KiB

Shader "Hidden/HDRenderPipeline/Sky/SkyProcedural"
{
SubShader
{
Pass
{
ZWrite Off
ZTest Always
Blend One OneMinusSrcAlpha, Zero One
Cull Off
HLSLPROGRAM
#pragma target 4.5
#pragma only_renderers d3d11 ps4 metal // TEMP: until we go further in dev
#pragma vertex Vert
#pragma fragment Frag
#pragma multi_compile _ ATMOSPHERICS_DEBUG
#pragma multi_compile _ PERFORM_SKY_OCCLUSION_TEST
#include "../../../../Core/ShaderLibrary/Color.hlsl"
#include "../../../../Core/ShaderLibrary/Common.hlsl"
#include "../../../../Core/ShaderLibrary/CommonLighting.hlsl"
#include "../../../ShaderVariables.hlsl"
TEXTURECUBE(_Cubemap);
SAMPLERCUBE(sampler_Cubemap);
float4x4 _PixelCoordToViewDirWS; // Actually just 3x3, but Unity can only set 4x4
// x exposure, y multiplier, z rotation
float4 _SkyParam;
float _SkyDepth;
float _DisableSkyOcclusionTest;
#define IS_RENDERING_SKY
#include "AtmosphericScattering.hlsl"
struct Attributes
{
uint vertexID : SV_VertexID;
};
struct Varyings
{
float4 positionCS : SV_POSITION;
};
Varyings Vert(Attributes input)
{
Varyings output;
output.positionCS = GetFullScreenTriangleVertexPosition(input.vertexID, UNITY_RAW_FAR_CLIP_VALUE);
return output;
}
float4 Frag(Varyings input) : SV_Target
{
// Points towards the camera
float3 viewDirWS = normalize(mul(float3(input.positionCS.xy, 1.0), (float3x3)_PixelCoordToViewDirWS));
// Reverse it to point into the scene
float3 dir = -viewDirWS;
// Rotate direction
float phi = DegToRad(_SkyParam.z);
float cosPhi, sinPhi;
sincos(phi, sinPhi, cosPhi);
float3 rotDirX = float3(cosPhi, 0, -sinPhi);
float3 rotDirY = float3(sinPhi, 0, cosPhi);
float3 rotatedDir = float3(dot(rotDirX, dir), dir.y, dot(rotDirY, dir));
// input.positionCS is SV_Position
PositionInputs posInput = GetPositionInput(input.positionCS.xy, _ScreenSize.zw);
#ifdef PERFORM_SKY_OCCLUSION_TEST
// Determine whether the sky is occluded by the scene geometry.
// Do not perform blending with the environment map if the sky is occluded.
float depthRaw = max(_SkyDepth, LOAD_TEXTURE2D(_MainDepthTexture, posInput.unPositionSS).r);
float skyTexWeight = (depthRaw > _SkyDepth) ? 0.0 : 1.0;
#else
float depthRaw = _SkyDepth;
float skyTexWeight = 1.0;
#endif
if (_DisableSkyOcclusionTest != 0.0)
{
depthRaw = _SkyDepth;
skyTexWeight = 1.0;
}
// Since we only need the world space position, so we don't pass the view-projection matrix.
UpdatePositionInput(depthRaw, _InvViewProjMatrix, k_identity4x4, posInput);
float4 c1, c2, c3;
VolundTransferScatter(GetAbsolutePositionWS(posInput.positionWS), c1, c2, c3);
float4 coord1 = float4(c1.rgb + c3.rgb, max(0.f, 1.f - c1.a - c3.a));
float3 coord2 = c2.rgb;
float sunCos = dot(normalize(dir), _SunDirection);
float miePh = MiePhase(sunCos, _MiePhaseAnisotropy);
float2 occlusion = float2(1.0, 1.0); // TODO.
float extinction = coord1.a;
float3 scatter = coord1.rgb * occlusion.x + coord2 * miePh * occlusion.y;
#ifdef ATMOSPHERICS_DEBUG
switch (_AtmosphericsDebugMode)
{
case ATMOSPHERICS_DBG_RAYLEIGH: return c1;
case ATMOSPHERICS_DBG_MIE: return c2 * miePh;
case ATMOSPHERICS_DBG_HEIGHT: return c3;
case ATMOSPHERICS_DBG_SCATTERING: return float4(scatter, 0.0);
case ATMOSPHERICS_DBG_OCCLUSION: return float4(occlusion.xy, 0.0, 0.0);
case ATMOSPHERICS_DBG_OCCLUDEDSCATTERING: return float4(scatter, 0.0);
}
#endif
float3 skyColor = float3(0.0, 0.0, 0.0);
// Opacity should be proportional to extinction, but this produces wrong results.
// It appears what the algorithm computes is not actually extinction.
float opacity = (1.0 - extinction);
if (skyTexWeight == 1.0)
{
skyColor = SAMPLE_TEXTURECUBE_LOD(_Cubemap, sampler_Cubemap, rotatedDir, 0).rgb;
skyColor *= exp2(_SkyParam.x) * _SkyParam.y;
opacity = 1.0; // Fully overwrite unoccluded scene regions.
}
float3 atmosphereColor = ClampToFloat16Max(skyColor * extinction + scatter);
// Apply the atmosphere on top of the scene using premultiplied alpha blending.
return float4(atmosphereColor, opacity);
}
ENDHLSL
}
}
Fallback Off
}