Rayと変換座標が適応された図形との当たり判定

transformedRaySample.cpp

# include <Siv3D.hpp> // Siv3D v0.6.12

Ray transformedRay(const Ray& ray, const Mat4x4& mat) {
	return Ray(mat.transformPoint(ray.getOrigin()), mat.transformPoint(ray.getDirection()).withLength(1));
}

struct HexFace {
	static Vec3 getFaceNormal(uint8 i) {
		static std::array<Vec3, 6> normals{
			Vec3{-1, 0, 0},
				Vec3{ 0,-1,0 },
				Vec3{ 0,0,-1 },
				Vec3{ 1,0,0 },
				Vec3{ 0,1,0 },
				Vec3{ 0,0,1 }
		};
		return normals[i];
	}
	Optional<std::pair<uint8, double>> intersects(const Ray& ray) {
		double min = Math::Inf;
		uint8 faceNum;
		for (auto i : step(6)) {
			Mat4x4 mat(Quaternion::FromUnitVectors({ 0,1,0 }, getFaceNormal(i)));
			if (auto distance = Plane({ 0,0.5,0 }, 1).intersects(transformedRay(ray, mat.inverse()))) {
				if (*distance < min) {
					min = *distance;
					faceNum = i;
				}
			}
		}
		if (not IsInfinity(min)) {
			return { {faceNum,min} };
		}
		return none;
	}
	void draw()const {
		Box(1).draw();
	}
	void draw(uint8 faceNum)const {
		Box(1).draw();
		Mat4x4 mat(Quaternion::FromUnitVectors({ 0,1,0 }, getFaceNormal(faceNum)));
		Transformer3D tf{ mat };
		Plane({ 0,0.51,0 }, 1).draw(Linear::Palette::Pink);
	}
};

void Main()
{
	const ColorF backgroundColor = ColorF{ 0.4, 0.6, 0.8 }.removeSRGBCurve();
	const MSRenderTexture renderTexture{ Scene::Size(), TextureFormat::R8G8B8A8_Unorm_SRGB, HasDepth::Yes };

	HexFace hexFace;
	BasicCamera3D camera{ renderTexture.size(),30_deg,{0,0,-10} };

	Quaternion quaternion = Quaternion::Identity();

	while (System::Update())
	{
		ClearPrint();
		if (MouseL.pressed()) {
			if (not Cursor::DeltaF().isZero()) {
				quaternion *= Quaternion::RotationNormal({ Cursor::DeltaF().yx().normalized(),0 }, -Cursor::DeltaF().length() / 200);
			}
		}
		if (MouseR.pressed()) {
			quaternion *= Quaternion::RotationNormal({ 0,0,1 }, -(Cursor::PosF() - Scene::CenterF()).normalized().cross(Cursor::DeltaF()) / 200);
		}

		Graphics3D::SetCameraTransform(camera);
		{
			const ScopedRenderTarget3D target{ renderTexture.clear(backgroundColor) };

			Transformer3D tf{ Mat4x4(quaternion) };

			Ray ray = camera.screenToRay(Cursor::PosF());

			if (auto opt = hexFace.intersects(transformedRay(ray,Graphics3D::GetLocalTransform().inverse()))) {
				auto& [index, dist] = *opt;
				hexFace.draw(index);
			}
			else {
				hexFace.draw();
			}
		}
		
		Graphics3D::Flush();
		renderTexture.resolve();
		Shader::LinearToScreen(renderTexture);
	}
}