2DLightBloom.hpp

#pragma once
#include <Siv3D.hpp>

// https://siv3d.github.io/ja-jp/sample/visual/#2d
class LightBloom2D
{
protected:
	Size sceneSize;
	RenderTexture gaussianA1, gaussianB1;
	RenderTexture gaussianA4, gaussianB4;
	RenderTexture gaussianA8, gaussianB8;

public:
	explicit LightBloom2D(const Size& sceneSize)
		: sceneSize(sceneSize),
		  gaussianA1(sceneSize), gaussianB1(sceneSize),
		  gaussianA4(sceneSize / 4), gaussianB4(sceneSize / 4),
		  gaussianA8(sceneSize / 8), gaussianB8(sceneSize / 8)
	{
		init();
	}

	void init()
	{
		gaussianA1.clear(ColorF(0.0));
	}
	void clear()
	{
		gaussianA1.clear(ColorF(0.0));
		gaussianA4.clear(ColorF(0.0));
		gaussianA8.clear(ColorF(0.0));
	}

	void draw(double a8 = 1, double a4 = 1, double a1 = 1)
	{
		// オリジナルサイズのガウスぼかし (A1)
		// A1 を 1/4 サイズにしてガウスぼかし (A4)
		// A4 を 1/2 サイズにしてガウスぼかし (A8)
		Shader::GaussianBlur(gaussianA1, gaussianB1, gaussianA1);
		Shader::Downsample(gaussianA1, gaussianA4);
		Shader::GaussianBlur(gaussianA4, gaussianB4, gaussianA4);
		Shader::Downsample(gaussianA4, gaussianA8);
		Shader::GaussianBlur(gaussianA8, gaussianB8, gaussianA8);

		ScopedRenderStates2D blend(BlendState::Additive);
		if (a1)
			gaussianA1.resized(sceneSize).draw(ColorF(a1));
		if (a4)
			gaussianA4.resized(sceneSize).draw(ColorF(a4));
		if (a8)
			gaussianA8.resized(sceneSize).draw(ColorF(a8));
	}

	using RenderScope = std::pair<ScopedRenderTarget2D, ScopedRenderStates2D>;

	[[nodiscard]] RenderScope makeRenderScope() const
	{
		return std::make_pair(ScopedRenderTarget2D(gaussianA1), ScopedRenderStates2D(BlendState::Additive));
	}

private:
	class ScopedLightBloom : Uncopyable
	{
	private:
		friend class LightBloom2D;

		Optional<RenderScope> rs;
		std::reference_wrapper<LightBloom2D> _this;
		double a8, a4, a1;

		ScopedLightBloom(Optional<RenderScope>&& rs, LightBloom2D& _this, double a8, double a4, double a1)
			: rs(std::move(rs)), _this(_this),
			  a8(a8), a4(a4), a1(a1)
		{
			_this.init();
		}

	public:
		~ScopedLightBloom()
		{
			rs.reset();
			_this.get().draw(a8, a4, a1);
		}
	};

public:
	[[nodiscard]] auto makeLightBloomScope(double a8 = 1, double a4 = 1, double a1 = 1)
	{
		return ScopedLightBloom(makeRenderScope(), *this, a8, a4, a1);
	}
};

void DrawScene()
{
	Circle(680, 40, 20).draw();
	Rect(Arg::center(680, 110), 30).draw();
	Triangle(680, 180, 40).draw();

	Circle(740, 40, 20).draw(HSV(0));
	Rect(Arg::center(740, 110), 30).draw(HSV(120));
	Triangle(740, 180, 40).draw(HSV(240));

	Circle(50, 200, 300).drawFrame(4);
	Circle(550, 450, 200).drawFrame(4);

	for (auto i : step(12))
	{
		const double angle = i * 30_deg + Scene::Time() * 5_deg;
		const Vec2 pos = OffsetCircular(Scene::Center(), 200, angle);
		Circle(pos, 8).draw(HSV(i * 30));
	}
}

void GUI(const Vec2& pos, double& a8, double& a4, double& a1) {
	SimpleGUI::Slider(U"a8: {:.1f}"_fmt(a8), a8, 0.0, 4.0, pos);
	SimpleGUI::Slider(U"a4: {:.1f}"_fmt(a4), a4, 0.0, 4.0, pos.movedBy(0, 40));
	SimpleGUI::Slider(U"a1: {:.1f}"_fmt(a1), a1, 0.0, 4.0, pos.movedBy(0, 80));

	if (SimpleGUI::Button(U"0, 0, 0", pos.movedBy(0, 120))) {
		a8 = a4 = a1 = 0.0;
	}
	if (SimpleGUI::Button(U"1, 0, 0", pos.movedBy(0, 160))) {
		a8 = 1.0;
		a4 = a1 = 0.0;
	}
	if (SimpleGUI::Button(U"1, 1, 0", pos.movedBy(0, 200))) {
		a8 = a4 = 1.0;
		a1 = 0.0;
	}
	if (SimpleGUI::Button(U"1, 1, 1", pos.movedBy(0, 240))) {
		a8 = a4 = a1 = 1.0;
	}
}

void Main()
{
	constexpr Size sceneSize(800, 600);

	LightBloom2D lightbloom(sceneSize);

	double a8 = 1, a4 = 1, a1 = 1;

	while (System::Update())
	{
		DrawScene();

		//*
		lightbloom.init();
		{
			auto rs = lightbloom.makeRenderScope();
			DrawScene();
		}
		lightbloom.draw(a8, a4, a1);
		//*/

		/*
		{
			auto rs = lightbloom.makeLightBloomScope(a8, a4, a1);
			DrawScene();
		}
		//*/

		GUI({ 20,20 }, a8, a4, a1);
	}
}