1 files changed, 67 insertions, 0 deletions
diff --git a/gfx/frustum.cpp b/gfx/frustum.cpp
new file mode 100644
index 0000000..faa676d
--- /dev/null
+++ b/gfx/frustum.cpp
@@ -0,0 +1,67 @@
+#include "frustum.h"
+#include <algorithm>
+#include <collections.h>
+#include <glm/ext/matrix_transform.hpp>
+
+static constexpr auto PLANES = std::array {0, 1, 2} * std::array {-1.F, 1.F};
+
+Frustum::Frustum(const GlobalPosition3D & pos, const glm::mat4 & view, const glm::mat4 & projection) :
+	position {pos}, view {view}, projection {projection}, viewProjection {}, inverseViewProjection {}, planes {}
+{
+	updateCache();
+}
+
+void
+Frustum::updateView(const glm::mat4 & newView)
+{
+	view = newView;
+	updateCache();
+}
+
+bool
+Frustum::contains(const BoundingBox & aabb) const
+{
+	return boundByPlanes(aabb, FACES);
+}
+
+bool
+Frustum::shadedBy(const BoundingBox & aabb) const
+{
+	return boundByPlanes(aabb, FACES - 1);
+}
+
+bool
+Frustum::boundByPlanes(const BoundingBox & aabb, size_t nplanes) const
+{
+	static constexpr auto EXTENT_CORNER_IDXS = [] {
+		using Extent = GlobalPosition3D BoundingBox::*;
+		constexpr auto EXTENTS = std::array {&BoundingBox::min, &BoundingBox::max};
+		std::array<glm::vec<3, Extent>, 2ZU * 2ZU * 2ZU> out {};
+		std::ranges::copy(std::views::cartesian_product(EXTENTS, EXTENTS, EXTENTS)
+						| std::views::transform(
+								std::make_from_tuple<glm::vec<3, Extent>, std::tuple<Extent, Extent, Extent>>),
+				out.begin());
+		return out;
+	}();
+
+	const std::array<RelativePosition4D, 8> corners
+			= EXTENT_CORNER_IDXS * [relativeAabb = aabb - position](auto idxs) -> glm::vec4 {
+		return {(relativeAabb.*(idxs.x)).x, (relativeAabb.*(idxs.y)).y, (relativeAabb.*(idxs.z)).z, 1.F};
+	};
+	return std::ranges::none_of(std::span(planes).subspan(0, nplanes), [&corners](const auto & frustumPlane) {
+		return (std::ranges::all_of(corners, [&frustumPlane](const auto & corner) {
+			return glm::dot(frustumPlane, corner) < 0.F;
+		}));
+	});
+}
+
+void
+Frustum::updateCache()
+{
+	viewProjection = projection * view;
+	inverseViewProjection = glm::inverse(viewProjection);
+	std::ranges::transform(PLANES, planes.begin(), [vpt = glm::transpose(viewProjection)](const auto & idxs) {
+		const auto [idx, sgn] = idxs;
+		return vpt[3] + (vpt[idx] * sgn);
+	});
+}