SceneRenderer.hpp

#pragma once

#include <Siv3D.hpp>
#include "Scene.hpp"
#include "Utils.hpp"
#include "Constants.hpp"
#include "Material.hpp"

namespace RayT {
	struct SceneRenderer {
		Scene scene;

		explicit SceneRenderer(const Scene _scene)
			: scene(_scene)
		{ }

		// 光線を飛ばして投影面の色を返す
		ColorF color(const Ray ray, const int depth = 0) const
		{
			if (depth > Constants::MaxRecurse)
				return Palette::Black;

			auto hitRec = scene.trace(ray);
			if (hitRec)
			{
				const auto scatterRec = hitRec->materialPtr->scatter(ray, hitRec.value());
				if (scatterRec)
				{
					return color(scatterRec->ray, depth + 1) * scatterRec->albedo;
				}

				return Palette::Black;
			}

			const double lerpT = ray.direction.y + 1.0 * 0.5;
			return ColorF(1.0, 1.0, 1.0).lerp(ColorF(0.5, 0.7, 1.0), lerpT);
		}

		// 複数の光線を飛ばしてサンプリングした投影面の色を返す
		ColorF sampleColor(const Vec2 imagePlanePos, const int samples) const
		{
			ColorF result(0.0, 0.0, 0.0);

			for (const auto i : step(samples))
			{
				const auto sampleRandomMax = scene.imagePlane.size / scene.camera.resolution;
				const auto sampleImagePlanePos = imagePlanePos + RandomVec2(sampleRandomMax.x, sampleRandomMax.y);

				const auto sampleColor = color(scene.rayAt(sampleImagePlanePos));
				result += sampleColor;
			}

			result *= 1.0 / samples;

			return result;
		}

		// レンダリング
		Image render(const int samples) const
		{
			Image image(scene.camera.resolution);

#pragma omp parallel for schedule(dynamic)
			for (int y = 0; y < scene.camera.resolution.y; ++y)
			{
				const double imagePlaneX = scene.imagePlane.size.y * (static_cast<double>(y) / scene.camera.resolution.y);

				for (int x = 0; x < scene.camera.resolution.x; ++x)
				{
					const double imagePlaneY = scene.imagePlane.size.x * (static_cast<double>(x) / scene.camera.resolution.x);

					// 投影面上の座標
					const Vec2 imagePlanePos(imagePlaneY, imagePlaneX);

					// 色を計算する
					// サンプル数1の場合はサンプリングしない
					const auto pointColor =
						samples == 1
						? color(scene.rayAt(imagePlanePos))
						: sampleColor(imagePlanePos, samples);

					Point(x, y).overwrite(image, Utils::LinearToGamma(pointColor, Constants::GammaValue));
				}
			}

			return image;
		}
	};
}