Bloom.h

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#pragma once
#include "common/Export.h"
 
#include <array>
#include "common/Result.h"
 
namespace eve::graphics {
 
class Canvas;
class Graphics;
class Shader;
class Texture;
 
enum class BloomFilter { KarisTent, GaussianScatter, GaussianPyramid };
 
struct BloomFilterSettings {
    BloomFilter filter        = BloomFilter::KarisTent;
    float       scatter       = 0.68f;
    int         maxIterations = 6;
    float       clamp         = 65472.f;
};
 
[[nodiscard]] EVENGINE_API_BACKENDS Result<void> validateBloomFilterSettings(const BloomFilterSettings &settings);
 
class EVENGINE_API_BACKENDS Bloom {
public:
    explicit Bloom(Graphics *gfx);
 
    [[nodiscard]] Result<void> configureFilter(const BloomFilterSettings &settings);
    BloomFilterSettings filterSettings() const { return filterSettings_; }
 
    Texture *build(Texture *source, float threshold, float scatter = 1.f);
 
    Texture *apply(Texture *source, float intensity, float threshold, float scatter = 1.f);
 
private:
    Texture                 *buildGaussian(Texture *source, float threshold);
    Texture                 *compositeGaussian(Texture *source, Texture *bloom, float intensity);
    BloomFilterSettings      filterSettings_{};
    Shader                  *gaussianShader_ = nullptr;
    std::array<Canvas *, 16> gaussianDown_{};
    std::array<Canvas *, 16> gaussianUp_{};
    void ensureTargets(int sourceWidth, int sourceHeight);
    void configureDownsample(Texture *source, bool firstPass, float threshold);
    void configureUpsample(Texture *source, float scatter);
 
    Graphics *gfx_ = nullptr;
    Shader *downsample_ = nullptr;
    Shader *upsample_ = nullptr;
    std::array<Canvas *, 4> levels_{};
    Canvas *composite_ = nullptr;
    int sourceWidth_ = 0;
    int sourceHeight_ = 0;
};
 
}  // namespace eve::graphics