Checkerboard was wrongfully added to the counting branch, so we copied it over

RayTracer/material/texture/Checkerboard.cpp

+#include "Checkerboard.h"
+
+namespace material {
+Checkerboard::Checkerboard(int size) : size(size) {
+}
+util::Vec3 Checkerboard::color(float x, float y) const {
+	util::Vec3 color(0);
+	bool hori = (int)(x * size) % 2 == 0;
+	bool verti = (int)(y * size) % 2 == 0;
+	if (hori ^ verti) color = util::Vec3(1);
+	return color;
+}
+}  // namespace material
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RayTracer/material/texture/Checkerboard.h

+#pragma once
+
+#include "../../sampling/Sampler.h"
+
+namespace material {
+class Checkerboard : public util::Sampler {
+   public:
+	Checkerboard(int size);
+	util::Vec3 color(float x, float y) const override;
+
+   private:
+	float size;
+};
+}  // namespace material
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