IVSmokeVSMProcessor.cpp

// Copyright (c) 2026, Team SDB. All rights reserved.
 
#include "IVSmokeVSMProcessor.h"
#include "IVSmokeCSMRenderer.h"
#include "IVSmokeShaders.h"
#include "IVSmokePostProcessPass.h"
#include "RenderGraphBuilder.h"
#include "RenderGraphUtils.h"
#include "GlobalShader.h"
 
DEFINE_LOG_CATEGORY_STATIC(LogIVSmokeVSM, Log, All);
 
// ============================================================================
// Constructor / Destructor
// ============================================================================
 
FIVSmokeVSMProcessor::FIVSmokeVSMProcessor()
{
}
 
FIVSmokeVSMProcessor::~FIVSmokeVSMProcessor()
{
}
 
// ============================================================================
// Process
// ============================================================================
 
void FIVSmokeVSMProcessor::Process(
    FRDGBuilder& GraphBuilder,
    FRDGTextureRef DepthTexture,
    FRDGTextureRef VSMTexture,
    int32 BlurRadius)
{
    if (!DepthTexture || !VSMTexture)
    {
        return;
    }
 
    // Step 1: Convert depth to variance
    AddDepthToVariancePass(GraphBuilder, DepthTexture, VSMTexture);
 
    // Step 2: Apply blur if radius > 0
    if (BlurRadius > 0)
    {
        const FIntPoint TextureSize(VSMTexture->Desc.Extent.X, VSMTexture->Desc.Extent.Y);
 
        // Create temporary texture for ping-pong blur
        FRDGTextureDesc TempDesc = FRDGTextureDesc::Create2D(
            TextureSize,
            PF_G32R32F,  // RG32F for variance
            FClearValueBinding::None,
            TexCreate_ShaderResource | TexCreate_UAV
        );
        FRDGTextureRef TempTexture = GraphBuilder.CreateTexture(TempDesc, TEXT("IVSmokeVSMBlurTemp"));
 
        // Horizontal blur: VSMTexture -> TempTexture
        AddHorizontalBlurPass(GraphBuilder, VSMTexture, TempTexture, BlurRadius);
 
        // Vertical blur: TempTexture -> VSMTexture
        AddVerticalBlurPass(GraphBuilder, TempTexture, VSMTexture, BlurRadius);
    }
}
 
void FIVSmokeVSMProcessor::ProcessCascades(
    FRDGBuilder& GraphBuilder,
    TArray<FIVSmokeCascadeData>& Cascades,
    int32 BlurRadius)
{
    for (int32 CascadeIndex = 0; CascadeIndex < Cascades.Num(); CascadeIndex++)
    {
        FIVSmokeCascadeData& Cascade = Cascades[CascadeIndex];
 
        if (!Cascade.DepthRT || !Cascade.VSMRT)
        {
            continue;
        }
 
        // Register external textures (include cascade index for RenderDoc debugging)
        FRDGTextureRef DepthRDG = GraphBuilder.RegisterExternalTexture(
            CreateRenderTarget(
                Cascade.DepthRT->GetRenderTargetResource()->GetRenderTargetTexture(),
                *FString::Printf(TEXT("IVSmokeCSMDepth_%d"), CascadeIndex)
            )
        );
 
        FRDGTextureRef VSMRDG = GraphBuilder.RegisterExternalTexture(
            CreateRenderTarget(
                Cascade.VSMRT->GetRenderTargetResource()->GetRenderTargetTexture(),
                *FString::Printf(TEXT("IVSmokeCSMVSM_%d"), CascadeIndex)
            )
        );
 
        Process(GraphBuilder, DepthRDG, VSMRDG, BlurRadius);
    }
}
 
// ============================================================================
// Depth to Variance Pass
// ============================================================================
 
void FIVSmokeVSMProcessor::AddDepthToVariancePass(
    FRDGBuilder& GraphBuilder,
    FRDGTextureRef DepthTexture,
    FRDGTextureRef VSMTexture)
{
    const FIntPoint TextureSize(DepthTexture->Desc.Extent.X, DepthTexture->Desc.Extent.Y);
 
    FGlobalShaderMap* ShaderMap = GetGlobalShaderMap(GMaxRHIFeatureLevel);
    TShaderMapRef<FIVSmokeDepthToVarianceCS> ComputeShader(ShaderMap);
 
    auto* Parameters = GraphBuilder.AllocParameters<FIVSmokeDepthToVarianceCS::FParameters>();
    Parameters->DepthTexture = DepthTexture;
    Parameters->VarianceTexture = GraphBuilder.CreateUAV(VSMTexture);
    Parameters->TextureSize = TextureSize;
 
    FIVSmokePostProcessPass::AddComputeShaderPass<FIVSmokeDepthToVarianceCS>(
        GraphBuilder,
        ShaderMap,
        ComputeShader,
        Parameters,
        FIntVector(TextureSize.X, TextureSize.Y, 1)
    );
}
 
// ============================================================================
// Blur Passes
// ============================================================================
 
void FIVSmokeVSMProcessor::AddHorizontalBlurPass(
    FRDGBuilder& GraphBuilder,
    FRDGTextureRef SourceTexture,
    FRDGTextureRef DestTexture,
    int32 BlurRadius)
{
    const FIntPoint TextureSize(SourceTexture->Desc.Extent.X, SourceTexture->Desc.Extent.Y);
 
    FGlobalShaderMap* ShaderMap = GetGlobalShaderMap(GMaxRHIFeatureLevel);
    TShaderMapRef<FIVSmokeVSMBlurCS> ComputeShader(ShaderMap);
 
    auto* Parameters = GraphBuilder.AllocParameters<FIVSmokeVSMBlurCS::FParameters>();
    Parameters->SourceTexture = SourceTexture;
    Parameters->DestTexture = GraphBuilder.CreateUAV(DestTexture);
    Parameters->LinearClampSampler = TStaticSamplerState<SF_Bilinear, AM_Clamp, AM_Clamp, AM_Clamp>::GetRHI();
    Parameters->TextureSize = TextureSize;
    Parameters->BlurRadius = BlurRadius;
    Parameters->BlurDirection = 0;  // Horizontal
 
    FIVSmokePostProcessPass::AddComputeShaderPass<FIVSmokeVSMBlurCS>(
        GraphBuilder,
        ShaderMap,
        ComputeShader,
        Parameters,
        FIntVector(TextureSize.X, TextureSize.Y, 1)
    );
}
 
void FIVSmokeVSMProcessor::AddVerticalBlurPass(
    FRDGBuilder& GraphBuilder,
    FRDGTextureRef SourceTexture,
    FRDGTextureRef DestTexture,
    int32 BlurRadius)
{
    const FIntPoint TextureSize(SourceTexture->Desc.Extent.X, SourceTexture->Desc.Extent.Y);
 
    FGlobalShaderMap* ShaderMap = GetGlobalShaderMap(GMaxRHIFeatureLevel);
    TShaderMapRef<FIVSmokeVSMBlurCS> ComputeShader(ShaderMap);
 
    auto* Parameters = GraphBuilder.AllocParameters<FIVSmokeVSMBlurCS::FParameters>();
    Parameters->SourceTexture = SourceTexture;
    Parameters->DestTexture = GraphBuilder.CreateUAV(DestTexture);
    Parameters->LinearClampSampler = TStaticSamplerState<SF_Bilinear, AM_Clamp, AM_Clamp, AM_Clamp>::GetRHI();
    Parameters->TextureSize = TextureSize;
    Parameters->BlurRadius = BlurRadius;
    Parameters->BlurDirection = 1;  // Vertical
 
    FIVSmokePostProcessPass::AddComputeShaderPass<FIVSmokeVSMBlurCS>(
        GraphBuilder,
        ShaderMap,
        ComputeShader,
        Parameters,
        FIntVector(TextureSize.X, TextureSize.Y, 1)
    );
}