IVSmokeHoleShaders.h

// Copyright (c) 2026, Team SDB. All rights reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "GlobalShader.h"
#include "ShaderParameterStruct.h"
 
class UIVSmokeHolePreset;
struct FIVSmokeHoleData;
 
//~============================================================================
// GPU Data Structure
 
/**
 * @struct FIVSmokeHoleGPU
 * @brief Built from FIVSmokeHoleData + UIVSmokeHolePreset at render time.
 */
struct alignas(16) FIVSmokeHoleGPU
{
    FIVSmokeHoleGPU() = default;
 
    /**
     * You can Constructs a FIVSmokeHoleGPU using DynamicHoleData, Preset, and server time.
     * @param DynamicHoleData       Dynamic hole data.
     * @param Preset                HolePreset defined as DataAsset.
     * @param CurrentServerTime     The CurrentServerTime is obtained through the GetSyncedTime function.
     */
    FIVSmokeHoleGPU(const FIVSmokeHoleData& DynamicHoleData, const UIVSmokeHolePreset& Preset, const float CurrentServerTime);
 
    //~============================================================================
    // Common
 
    /** The central point of hole creation. */
    FVector3f Position;
 
    /** Time after hole is called creation. */
    float CurLifeTime;
 
    /** 0 = Penetration, 1 = Explosion, 2 = Dynamic */
    int HoleType;
 
    /** Radius value used to calculate values related to the range. */
    float Radius;
 
    /** Total duration. */
    float Duration;
 
    /** Edge smooth range. */
    float Softness;
 
    //~============================================================================
    // Dynamic
 
    /** the size of a hole. */
    FVector3f Extent;
 
    float DynamicPadding;
 
    //~============================================================================
    // Explosion
 
    /** Expansion time used only for Explosion. */
    float ExpansionDuration;
 
    /** Current fadeRange extracted from ExpansionFadeRangeCurveOverTime with values normalized to expansion time. */
    float CurExpansionFadeRangeOverTime;
 
    /** Current fadeRange extracted from ShrinkFadeRangeCurveOverTime with values normalized to shrink time. */
    float CurShrinkFadeRangeOverTime;
 
    /** Exponential value of the calculation of the distortion value over expansion time. */
    float DistortionExpOverTime;
 
    /** Distortion degree max value. */
    float DistortionDistance;
 
    FVector3f PresetExplosionPadding;
 
    //~============================================================================
    // Penetration
 
    /** The point at which the trajectory of the penetration ends. */
    FVector3f EndPosition;
 
    /** Radius at the end position. */
    float EndRadius;
};
 
/**
 * @brief Compute shader that carves holes into 3D volume texture.
 */
class IVSMOKE_API FIVSmokeHoleCarveCS : public FGlobalShader
{
public:
    static constexpr uint32 ThreadGroupSizeX = 8;
    static constexpr uint32 ThreadGroupSizeY = 8;
    static constexpr uint32 ThreadGroupSizeZ = 8;
    static constexpr const TCHAR* EventName = TEXT("IVSmokeHoleCarveCS");
    DECLARE_GLOBAL_SHADER(FIVSmokeHoleCarveCS);
    SHADER_USE_PARAMETER_STRUCT(FIVSmokeHoleCarveCS, FGlobalShader);
 
public:
 
    BEGIN_SHADER_PARAMETER_STRUCT(FParameters, )
        // Output: 3D Volume Texture (Read and Write) - R16G16B16A16_UNORM channel
        SHADER_PARAMETER_RDG_TEXTURE_UAV(RWTexture3D<float4>, VolumeTexture)
 
        // Input: Hole data buffer (unified structure)
        SHADER_PARAMETER_RDG_BUFFER_SRV(StructuredBuffer<FIVSmokeHoleGPU>, HoleBuffer)
 
        // Volume bounds (local space)
        SHADER_PARAMETER(FVector3f, VolumeMin)
        SHADER_PARAMETER(FVector3f, VolumeMax)
 
        // Volume resolution
        SHADER_PARAMETER(FIntVector, Resolution)
 
        // Hole parameters
        SHADER_PARAMETER(int32, NumHoles)
 
        // Noise textures (per HoleType)
        SHADER_PARAMETER_TEXTURE(Texture2D, PenetrationNoiseTexture)
        SHADER_PARAMETER_TEXTURE(Texture2D, ExplosionNoiseTexture)
        SHADER_PARAMETER_TEXTURE(Texture2D, DynamicNoiseTexture)
        SHADER_PARAMETER_SAMPLER(SamplerState, NoiseSampler)
 
        // Noise parameters (per HoleType)
        SHADER_PARAMETER(float, PenetrationNoiseStrength)
        SHADER_PARAMETER(float, PenetrationNoiseScale)
        SHADER_PARAMETER(float, ExplosionNoiseStrength)
        SHADER_PARAMETER(float, ExplosionNoiseScale)
        SHADER_PARAMETER(float, DynamicNoiseStrength)
        SHADER_PARAMETER(float, DynamicNoiseScale)
    END_SHADER_PARAMETER_STRUCT()
 
    static bool ShouldCompilePermutation(const FGlobalShaderPermutationParameters& Parameters)
    {
        return IsFeatureLevelSupported(Parameters.Platform, ERHIFeatureLevel::SM5);
    }
 
    static void ModifyCompilationEnvironment(
        const FGlobalShaderPermutationParameters& Parameters,
        FShaderCompilerEnvironment& OutEnvironment
    )
    {
        FGlobalShader::ModifyCompilationEnvironment(Parameters, OutEnvironment);
        OutEnvironment.SetDefine(TEXT("THREADGROUP_SIZEX"), ThreadGroupSizeX);
        OutEnvironment.SetDefine(TEXT("THREADGROUP_SIZEY"), ThreadGroupSizeY);
        OutEnvironment.SetDefine(TEXT("THREADGROUP_SIZEZ"), ThreadGroupSizeZ);
    }
};
 
/**
 * @brief Compute shader for 1D separable blur on 3D volume texture.
 *        Run 3 times (X, Y, Z axis) for full 3D Gaussian blur.
 */
class IVSMOKE_API FIVSmokeHoleBlurCS : public FGlobalShader
{
public:
    static constexpr uint32 ThreadGroupSizeX = 8;
    static constexpr uint32 ThreadGroupSizeY = 8;
    static constexpr uint32 ThreadGroupSizeZ = 8;
    static constexpr const TCHAR* EventName = TEXT("IVSmokeHoleBlurCS");
    DECLARE_GLOBAL_SHADER(FIVSmokeHoleBlurCS);
    SHADER_USE_PARAMETER_STRUCT(FIVSmokeHoleBlurCS, FGlobalShader);
 
public:
    BEGIN_SHADER_PARAMETER_STRUCT(FParameters, )
        // Input: Source volume texture
        SHADER_PARAMETER_RDG_TEXTURE_SRV(Texture3D<float4>, InputTexture)
        SHADER_PARAMETER_SAMPLER(SamplerState, InputSampler)
 
        // Output: Destination volume texture
        SHADER_PARAMETER_RDG_TEXTURE_UAV(RWTexture3D<float4>, OutputTexture)
 
        // Volume resolution
        SHADER_PARAMETER(FIntVector, Resolution)
 
        // Blur direction: (1,0,0) for X, (0,1,0) for Y, (0,0,1) for Z
        SHADER_PARAMETER(FIntVector, BlurDirection)
 
        // Blur radius in voxels
        SHADER_PARAMETER(int32, BlurStep)
    END_SHADER_PARAMETER_STRUCT()
 
    static bool ShouldCompilePermutation(const FGlobalShaderPermutationParameters& Parameters)
    {
        return IsFeatureLevelSupported(Parameters.Platform, ERHIFeatureLevel::SM5);
    }
 
    static void ModifyCompilationEnvironment(
        const FGlobalShaderPermutationParameters& Parameters,
        FShaderCompilerEnvironment& OutEnvironment
    )
    {
        FGlobalShader::ModifyCompilationEnvironment(Parameters, OutEnvironment);
        OutEnvironment.SetDefine(TEXT("THREADGROUP_SIZEX"), ThreadGroupSizeX);
        OutEnvironment.SetDefine(TEXT("THREADGROUP_SIZEY"), ThreadGroupSizeY);
        OutEnvironment.SetDefine(TEXT("THREADGROUP_SIZEZ"), ThreadGroupSizeZ);
    }
};