PlanarProjectedShadows.cpp

# include <Siv3D.hpp>

void Main()
{
	Window::Resize(1280, 720);
	const ColorF backgroundColor = ColorF{ 0.4, 0.6, 0.8 }.removeSRGBCurve();
	const Texture uvChecker{ U"example/texture/uv.png", TextureDesc::MippedSRGB };
	const MSRenderTexture renderTexture{ Scene::Size(), TextureFormat::R8G8B8A8_Unorm_SRGB, HasDepth::Yes };
	DebugCamera3D camera{ renderTexture.size(), 30_deg, Vec3{ 10, 16, -32 } };

	while (System::Update())
	{
		camera.update(2.0);
		Graphics3D::SetCameraTransform(camera);
		Graphics3D::SetGlobalAmbientColor(ColorF{ 0.2 });

		{
			const ScopedRenderTarget3D target{ renderTexture.clear(backgroundColor) };

			Plane{ 64 }.draw(uvChecker);
			Box{ -8,2,0,4 }.draw(ColorF{ 0.8, 0.6, 0.4 }.removeSRGBCurve());
			const double sphereY = (2 + Periodic::Jump0_1(2s) * 2);
			Sphere{ 0, sphereY, 0,2 }.draw(ColorF{ 0.4, 0.8, 0.6 }.removeSRGBCurve());
			Cylinder{ 8, 2, 0, 2, 4 }.draw(ColorF{ 0.6, 0.4, 0.8 }.removeSRGBCurve());

			// 平面投影の影を描画
			{
				// 3D モデルを平面化する変換行列
				const Mat4x4 shadowMatrix{ DirectX::XMMatrixShadow(SIMD_Float4{ 0, 1, 0, 0 }, SIMD_Float4{ Graphics3D::GetSunDirection(), 0 }) };
				const Transformer3D t{ shadowMatrix };

				// 深度バイアス
				RasterizerState rasterizerState = RasterizerState::Default3D;
				rasterizerState.depthBias = 300; // 床より少し浮かせる
				const ScopedRenderStates3D rs{ rasterizerState, BlendState::Default2D, DepthStencilState::DepthTest };

				const ColorF shadowColor = ColorF{ 0.0, 0.7 }.removeSRGBCurve();
				Box{ -8,2,0,4 }.draw(shadowColor);
				Sphere{ 0,sphereY,0,2 }.draw(shadowColor);
				Cylinder{ 8, 2, 0, 2, 4 }.draw(shadowColor);
			}
		}

		{
			Graphics3D::Flush();
			renderTexture.resolve();
			Shader::LinearToScreen(renderTexture);
		}
	}
}