IVSmokePostProcessPass.h

// Copyright (c) 2026, Team SDB. All rights reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "RenderGraphBuilder.h"
#include "RenderGraphUtils.h"
#include "ScreenPass.h"
#include "GlobalShader.h"
#include "ShaderParameterStruct.h"
#include "PixelShaderUtils.h"
 
/**
 * Core utility for dispatching PS/CS post process passes.
 * Designed for reusability - bring your own shader and parameters.
 */
 
class IVSMOKE_API FIVSmokePostProcessPass
{
public:
    /**
     * Add a fullscreen pixel shader pass.
     *
     * @param GraphBuilder    RDG builder
     * @param ShaderMap       Global shader map
     * @param PixelShader     Pixel shader to use
     * @param Parameters      Shader parameters (must have RenderTargets bound)
     * @param Output          Render target
     * @param Config          Pass configuration
     *
     * @warning Confirmed Engine Bug (UE 5.6 - UE 5.7)
     * The RDG Timeline View currently displays the raw format string (e.g., "IVSmoke::PixelShader: %s")
     * instead of the resolved variable name in Unreal Insights.
     *
     * Workaround:
     * 1. Select the event bar in Unreal Insights (Timing View).
     * 2. Check the Details Panel (Metadata) to view the correct shader name (e.g., MyShaderPS).
     *
     * https://issues.unrealengine.com/issue/UE-298245
     */
    template<typename TShaderClass>
    static void AddPixelShaderPass(
        FRDGBuilder& GraphBuilder,
        FGlobalShaderMap* ShaderMap,
        TShaderMapRef<TShaderClass> PixelShader,
        typename TShaderClass::FParameters* Parameters,
        const FScreenPassRenderTarget& Output);
 
    /**
     * Add a compute shader pass.
     *
     * @param GraphBuilder    RDG builder
     * @param ShaderMap       Global shader map
     * @param ComputeShader   Compute shader to use
     * @param Parameters      Shader parameters (must have UAV bound)
     * @param ViewportSize    Size of the viewport for thread dispatch
     * @param Config          Pass configuration
     *
     * @warning Confirmed Engine Bug (UE 5.6 - UE 5.7)
     * Similar to the Pixel Shader pass, the scope name appears as "IVSmoke::ComputeShader: %s"
     * in the Timing View due to the engine bug mentioned above.
     *
     * Please refer to the Details Panel in Unreal Insights for the correct shader name
     */
    template<typename TShaderClass>
    static void AddComputeShaderPass(
        FRDGBuilder& GraphBuilder,
        FGlobalShaderMap* ShaderMap,
        TShaderMapRef<TShaderClass> ComputeShader,
        typename TShaderClass::FParameters* Parameters,
        const FIntVector& TotalThreadSize);
 
    /**
     * Create an output texture suitable for UAV (compute shader).
     *
     * @param GraphBuilder    RDG builder
     * @param SourceTexture   Texture to base dimensions on
     * @param DebugName       Debug name for the new texture
     * @param OverrideFormat  Override pixel format (PF_Unknown = use source format)
     * @param OverrideExtent  Override texture extent (zero = use source extent)
     * @return New texture with UAV flag
     */
    static FRDGTextureRef CreateOutputTexture(
        FRDGBuilder& GraphBuilder,
        FRDGTextureRef SourceTexture,
        const TCHAR* DebugName = TEXT("IVSmokeOutput"),
        EPixelFormat OverrideFormat = PF_Unknown,
        FIntPoint OverrideExtent = FIntPoint::ZeroValue,
        ETextureCreateFlags Flags = ETextureCreateFlags::UAV);
};
//------------------------------------------------------------------------------
// Template implementations
//------------------------------------------------------------------------------
 
template<typename TShaderClass>
void FIVSmokePostProcessPass::AddPixelShaderPass(
    FRDGBuilder& GraphBuilder,
    FGlobalShaderMap* ShaderMap,
    TShaderMapRef<TShaderClass> PixelShader,
    typename TShaderClass::FParameters* Parameters,
    const FScreenPassRenderTarget& Output)
{
    RDG_EVENT_SCOPE(GraphBuilder, "IVSmoke::PixelShader: %s", TShaderClass::EventName);
 
    FPixelShaderUtils::AddFullscreenPass(
        GraphBuilder,
        ShaderMap,
        RDG_EVENT_NAME("%s", TShaderClass::EventName),
        PixelShader,
        Parameters,
        Output.ViewRect,
        TShaderClass::GetBlendState()
    );
}
 
template<typename TShaderClass>
void FIVSmokePostProcessPass::AddComputeShaderPass(
    FRDGBuilder& GraphBuilder,
    FGlobalShaderMap* ShaderMap,
    TShaderMapRef<TShaderClass> ComputeShader,
    typename TShaderClass::FParameters* Parameters,
    const FIntVector& TotalThreadSize)
{
    const uint32 GroupCountX = FMath::DivideAndRoundUp((uint32)TotalThreadSize.X, TShaderClass::ThreadGroupSizeX);
    const uint32 GroupCountY = FMath::DivideAndRoundUp((uint32)TotalThreadSize.Y, TShaderClass::ThreadGroupSizeY);
    const uint32 GroupCountZ = FMath::DivideAndRoundUp((uint32)TotalThreadSize.Z, TShaderClass::ThreadGroupSizeZ);
 
    RDG_EVENT_SCOPE(GraphBuilder, "IVSmoke::ComputeShader: %s", TShaderClass::EventName);
 
    FComputeShaderUtils::AddPass(
        GraphBuilder,
        RDG_EVENT_NAME("%s", TShaderClass::EventName),
        ComputeShader,
        Parameters,
        FIntVector(GroupCountX, GroupCountY, GroupCountZ)
    );
}