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Store the MIS data in an equiareal map

/main
Evgenii Golubev 8 年前
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3c94f605
共有 3 个文件被更改，包括 87 次插入 和 58 次删除
  1. 69
      Assets/ScriptableRenderLoop/HDRenderLoop/Sky/Resources/BuildProbabilityTables.compute
  2. 55
      Assets/ScriptableRenderLoop/HDRenderLoop/Sky/SkyManager.cs
  3. 21
      Assets/ScriptableRenderLoop/ShaderLibrary/ImageBasedLighting.hlsl

69
Assets/ScriptableRenderLoop/HDRenderLoop/Sky/Resources/BuildProbabilityTables.compute
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// 1. 1D texture with marginal densities, telling us the likelihood of selecting a particular row,
// 2. 2D texture with conditional densities, which correspond to the PDF of the texel given its row.
// Ref: PBRT v3, 13.6.7 "Piecewise-Constant 2D Distributions".
// Note that we use the equiareal mapping instead of the latitude-longitude one.
#include "ImageBasedLighting.hlsl"
#define TEXTURE_SIZE 256 // The size of the input texture
#define MIP1_SIZE TEXTURE_SIZE / 2 // The size of the MIP level 1 of the input texture
#define TEXTURE_HEIGHT 256 // MIS equiareal texture map: cos(theta) = 1.0 - 2.0 * v
#define TEXTURE_WIDTH 2 * TEXTURE_HEIGHT // MIS equiareal texture map: phi = TWO_PI * u
TEXTURE2D_ARRAY(envMap) // Cubemap as an array: [TEXTURE_SIZE x TEXTURE_SIZE x 6]
TEXTURECUBE(envMap) // Input cubemap
SAMPLERCUBE(sampler_envMap)
RWTexture2D<float> marginalRowDensities; // 1D texture: [(6 * MIP1_SIZE + 1) x 1]
RWTexture2D<float> conditionalDensities; // Array: [MIP1_SIZE x (6 * MIP1_SIZE)]
RWTexture2D<float> marginalRowDensities; // [(TEXTURE_HEIGHT + 1) x 1] (+ 1 for the image integral)
RWTexture2D<float> conditionalDensities; // [TEXTURE_WIDTH x TEXTURE_HEIGHT]
/* --- Implementation --- */

#pragma kernel ComputeConditionalDensities
groupshared float rowVals[SHARED_MEM(MIP1_SIZE)];
groupshared float rowVals[SHARED_MEM(TEXTURE_WIDTH)];
[numthreads(MIP1_SIZE / 2, 1, 1)]
[numthreads(TEXTURE_WIDTH / 2, 1, 1)]
// There are (MIP1_SIZE x 6) thread groups.
// A single thread group processes a row of MIP1_SIZE texels (2 per thread).
const uint n = MIP1_SIZE;
// There are TEXTURE_HEIGHT thread groups.
// A single thread group processes a row of TEXTURE_WIDTH texels (2 per thread).
const uint n = TEXTURE_WIDTH;
const uint k = groupId.y;
const uint jk = Mad24(k, n, j);
float w = TEXTURE_WIDTH;
float h = TEXTURE_HEIGHT;
float u1 = i1 / w + 0.5 / w;
float u2 = i2 / w + 0.5 / w;
float v = j / h + 0.5 / h;
float3 L1 = ConvertEquiarealToCubemap(u1, v);
float3 L2 = ConvertEquiarealToCubemap(u2, v);
float3 c1 = SAMPLE_TEXTURECUBE_LOD(envMap, sampler_envMap, L1, 0).rgb;
float3 c2 = SAMPLE_TEXTURECUBE_LOD(envMap, sampler_envMap, L2, 0).rgb;
// --------------------------------------------------------------------
// Compute the integral of the step function (row values).
// Perform a block-level parallel scan.

// Step 1: load the row of data into shared memory.
// We use MIP level 1 to account for interpolation during light sampling.
// Ref: PBRT v3, page 847.
float3 c1 = LOAD_TEXTURE2D_ARRAY_LOD(envMap, uint2(i1, j), k, 1).rgb;
float3 c2 = LOAD_TEXTURE2D_ARRAY_LOD(envMap, uint2(i2, j), k, 1).rgb;
rowVals[SHARED_MEM(i1)] = c1.r + c1.g + c1.b;
rowVals[SHARED_MEM(i2)] = c2.r + c2.g + c2.b;

if (i == 0)
{
float rowIntegralValue = rowValSum / n;
marginalRowDensities[uint2(jk, 0)] = rowIntegralValue;
marginalRowDensities[uint2(j, 0)] = rowIntegralValue;
// The exclusive scan requires the 1st element to be 0.
rowVals[SHARED_MEM(n - 1)] = 0.0;
}

GroupMemoryBarrierWithGroupSync();
// Compute the CDF. Note: the value at (i = n) is implicitly 1.
conditionalDensities[uint2(i1, jk)] = rowVals[SHARED_MEM(i1)] / rowValSum;
conditionalDensities[uint2(i2, jk)] = rowVals[SHARED_MEM(i2)] / rowValSum;
conditionalDensities[uint2(i1, j)] = rowVals[SHARED_MEM(i1)] / rowValSum;
conditionalDensities[uint2(i2, j)] = rowVals[SHARED_MEM(i2)] / rowValSum;
groupshared float rowInts[SHARED_MEM(8 * MIP1_SIZE)];
groupshared float rowInts[SHARED_MEM(TEXTURE_HEIGHT)];
[numthreads(8 * MIP1_SIZE / 2, 1, 1)]
[numthreads(TEXTURE_HEIGHT / 2, 1, 1)]
// The size of the input is (6 * MIP1_SIZE).
// However, the algorithm only works with inputs of sizes which are powers of 2,
// therefore there is a single thread group processing (8 * MIP1_SIZE) texels (2 per thread).
const uint sz = 6 * MIP1_SIZE;
const uint n = 8 * MIP1_SIZE;
// The size of the input is TEXTURE_HEIGHT. There is only one thread group.
const uint n = TEXTURE_HEIGHT;
const uint i = groupThreadId.x;
const uint i1 = i;
const uint i2 = i + n / 2;

// --------------------------------------------------------------------
// Step 1: load the row of data into shared memory.
rowInts[SHARED_MEM(i1)] = (i1 < sz) ? marginalRowDensities[uint2(i1, 0)] : 0.0;
rowInts[SHARED_MEM(i2)] = (i2 < sz) ? marginalRowDensities[uint2(i2, 0)] : 0.0;
rowInts[SHARED_MEM(i1)] = marginalRowDensities[uint2(i1, 0)];
rowInts[SHARED_MEM(i2)] = marginalRowDensities[uint2(i2, 0)];
uint offset;

if (i == 0)
{
float imgIntegralValue = rowIntSum / sz;
marginalRowDensities[uint2(sz, 0)] = imgIntegralValue;
float imgIntegralValue = rowIntSum / n;
marginalRowDensities[uint2(n, 0)] = imgIntegralValue;
// The exclusive scan requires the 1st element to be 0.
rowInts[SHARED_MEM(n - 1)] = 0.0;
}

GroupMemoryBarrierWithGroupSync();
// Compute the CDF. Note: the value at (i = n) is implicitly 1.
if (i1 < sz) { marginalRowDensities[uint2(i1, 0)] = rowInts[SHARED_MEM(i1)] / rowIntSum; }
if (i2 < sz) { marginalRowDensities[uint2(i2, 0)] = rowInts[SHARED_MEM(i2)] / rowIntSum; }
marginalRowDensities[uint2(i1, 0)] = rowInts[SHARED_MEM(i1)] / rowIntSum;
marginalRowDensities[uint2(i2, 0)] = rowInts[SHARED_MEM(i2)] / rowIntSum;
}

55
Assets/ScriptableRenderLoop/HDRenderLoop/Sky/SkyManager.cs
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bool m_UpdateRequired = true;
float m_CurrentUpdateTime = 0.0f;
// Configuration parameters for Multiple Importance Sampling.
const bool m_useMIS = false;
const int MIS_TEXTURE_HEIGHT = 256;
const int MIS_TEXTURE_WIDTH = MIS_TEXTURE_HEIGHT * 2;
SkyParameters m_SkyParameters = null;
public SkyParameters skyParameters

m_SkyboxGGXCubemapRT.filterMode = FilterMode.Trilinear;
m_SkyboxGGXCubemapRT.Create();
// + 1 because we store the value of the integral of the cubemap at the end of the texture.
m_SkyboxMarginalRowCdfRT = new RenderTexture(6 * resolution / 2 + 1, 1, 1, RenderTextureFormat.RFloat);
m_SkyboxMarginalRowCdfRT.dimension = TextureDimension.Tex2D;
m_SkyboxMarginalRowCdfRT.useMipMap = false;
m_SkyboxMarginalRowCdfRT.autoGenerateMips = false;
m_SkyboxMarginalRowCdfRT.enableRandomWrite = true;
m_SkyboxMarginalRowCdfRT.filterMode = FilterMode.Point;
m_SkyboxMarginalRowCdfRT.Create();
if (m_useMIS)
{
// + 1 because we store the value of the integral of the cubemap at the end of the texture.
m_SkyboxMarginalRowCdfRT = new RenderTexture(MIS_TEXTURE_HEIGHT + 1, 1, 1, RenderTextureFormat.RFloat);
m_SkyboxMarginalRowCdfRT.dimension = TextureDimension.Tex2D;
m_SkyboxMarginalRowCdfRT.useMipMap = false;
m_SkyboxMarginalRowCdfRT.autoGenerateMips = false;
m_SkyboxMarginalRowCdfRT.enableRandomWrite = true;
m_SkyboxMarginalRowCdfRT.filterMode = FilterMode.Point;
m_SkyboxMarginalRowCdfRT.Create();
m_SkyboxConditionalCdfRT = new RenderTexture(MIS_TEXTURE_WIDTH, MIS_TEXTURE_HEIGHT, 1, RenderTextureFormat.RFloat);
m_SkyboxConditionalCdfRT.dimension = TextureDimension.Tex2D;
m_SkyboxConditionalCdfRT.useMipMap = false;
m_SkyboxConditionalCdfRT.autoGenerateMips = false;
m_SkyboxConditionalCdfRT.enableRandomWrite = true;
m_SkyboxConditionalCdfRT.filterMode = FilterMode.Point;
}
m_SkyboxConditionalCdfRT = new RenderTexture(resolution / 2, 6 * resolution / 2, 1, RenderTextureFormat.RFloat);
m_SkyboxConditionalCdfRT.dimension = TextureDimension.Tex2D;
m_SkyboxConditionalCdfRT.useMipMap = false;
m_SkyboxConditionalCdfRT.autoGenerateMips = false;
m_SkyboxConditionalCdfRT.enableRandomWrite = true;
m_SkyboxConditionalCdfRT.filterMode = FilterMode.Point;
m_SkyboxConditionalCdfRT.Create();
}

m_Renderer.Build();
// TODO: We need to have an API to send our sky information to Enlighten. For now use a workaround through skybox/cubemap material...
m_StandardSkyboxMaterial = Utilities.CreateEngineMaterial("Skybox/Cubemap");
m_GGXConvolveMaterial = Utilities.CreateEngineMaterial("Hidden/HDRenderLoop/GGXConvolve");
m_StandardSkyboxMaterial = Utilities.CreateEngineMaterial("Skybox/Cubemap");
m_GGXConvolveMaterial = Utilities.CreateEngineMaterial("Hidden/HDRenderLoop/GGXConvolve");
m_BuildProbabilityTablesCS = Resources.Load<ComputeShader>("BuildProbabilityTables");
m_ConditionalDensitiesKernel = m_BuildProbabilityTablesCS.FindKernel("ComputeConditionalDensities");

private void BuildProbabilityTables(RenderLoop renderLoop)
{
// Bind the input cubemap as a Texture2DArray.
// TODO: for some reason, Unity only binds the first face...
// Bind the input cubemap.
m_BuildProbabilityTablesCS.SetTexture(m_ConditionalDensitiesKernel, "envMap", m_SkyboxCubemapRT);
// Bind the outputs.

// TODO: the shader has 'TEXTURE_SIZE' hard-coded to 256!
int mip1Size = (int)m_SkyParameters.resolution / 2;
cmd.DispatchCompute(m_BuildProbabilityTablesCS, m_ConditionalDensitiesKernel, mip1Size, 6, 1);
cmd.DispatchCompute(m_BuildProbabilityTablesCS, m_ConditionalDensitiesKernel, MIS_TEXTURE_HEIGHT, 1, 1);
cmd.DispatchCompute(m_BuildProbabilityTablesCS, m_MarginalRowDensitiesKernel, 1, 1, 1);
renderLoop.ExecuteCommandBuffer(cmd);
cmd.Dispose();

{
bool useMIS = false;
using (new Utilities.ProfilingSample("Sky Pass: GGX Convolution", renderLoop))
{
int mipCount = 1 + (int)Mathf.Log(input.width, 2.0f);

return;
}
if (useMIS)
if (m_useMIS)
{
BuildProbabilityTables(renderLoop);
}

m_GGXConvolveMaterial.SetTexture("_MainTex", input);
m_GGXConvolveMaterial.SetFloat("_InvOmegaP", invOmegaP);
if (useMIS)
if (m_useMIS)
{
m_GGXConvolveMaterial.SetTexture("_ConditionalDensities", m_SkyboxConditionalCdfRT);
m_GGXConvolveMaterial.SetTexture("_MarginalRowDensities", m_SkyboxMarginalRowCdfRT);

21
Assets/ScriptableRenderLoop/ShaderLibrary/ImageBasedLighting.hlsl
查看文件


return mipmapLevel / UNITY_SPECCUBE_LOD_STEPS;
}
// Performs conversion from equiareal map coordinates to cubemap (Cartesian) ones.
float3 ConvertEquiarealToCubemap(float u, float v)
{
// We have to convert the direction vector from the Spherical to the Cartesian coordinates:
// x = sin(theta) * sin(phi)
// y = cos(theta)
// z = sin(theta) * cos(phi)
// where our Equiareal map is defined as follows:
// phi = TWO_PI * u
// cos(theta) = 1.0 - 2.0 * v
// sin(theta) = sqrt(1.0 - cos^2(theta)) = 2.0 * sqrt(v - v * v)
float sinPhi, cosPhi;
sincos(TWO_PI * u, sinPhi, cosPhi);
float cosTheta = 1.0 - 2.0 * v;
float sinTheta = 2.0 * sqrt(v - v * v);
return float3(sinTheta * sinPhi, cosTheta, sinTheta * cosPhi);
}
// Ref: See "Moving Frostbite to PBR" Listing 22
// This formulation is for GGX only (with smith joint visibility or regular)
float3 GetSpecularDominantDir(float3 N, float3 R, float roughness)

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