Add function to test if an AABB is visible in a frustum

4 files changed, 38 insertions, 0 deletions

diff --git a/gfx/aabb.cpp b/gfx/aabb.cpp
index 862dacb..0a04ef4 100644
--- a/gfx/aabb.cpp
+++ b/gfx/aabb.cpp
@@ -22,3 +22,9 @@ AxisAlignedBoundingBox::operator+=(const GlobalPosition3D & point)
 	max = glm::max(max, point);
 	return *this;
 }
+
+AxisAlignedBoundingBox
+AxisAlignedBoundingBox::operator-(const GlobalPosition3D & viewPoint) const
+{
+	return {min - viewPoint, max - viewPoint};
+}
diff --git a/gfx/aabb.h b/gfx/aabb.h
index 568e91a..db3a215 100644
--- a/gfx/aabb.h
+++ b/gfx/aabb.h
@@ -11,6 +11,8 @@ public:
 
 	AxisAlignedBoundingBox & operator+=(const GlobalPosition3D & point);
 
+	AxisAlignedBoundingBox operator-(const GlobalPosition3D & viewPoint) const;
+
 	[[nodiscard]] static AxisAlignedBoundingBox fromPoints(std::span<const GlobalPosition3D> points);
 
 	GlobalPosition3D min, max;
diff --git a/gfx/frustum.cpp b/gfx/frustum.cpp
index a9dbdf0..8031d85 100644
--- a/gfx/frustum.cpp
+++ b/gfx/frustum.cpp
@@ -1,4 +1,5 @@
 #include "frustum.h"
+#include "aabb.h"
 #include <algorithm>
 #include <collections.h>
 #include <glm/ext/matrix_transform.hpp>
@@ -18,6 +19,31 @@ Frustum::updateView(const glm::mat4 & newView)
 	updateCache();
 }
 
+bool
+Frustum::contains(const AxisAlignedBoundingBox & aabb) const
+{
+	static constexpr auto EXTENT_CORNER_IDXS = [] {
+		using Extent = GlobalPosition3D AxisAlignedBoundingBox::*;
+		constexpr auto EXTENTS = std::array {&AxisAlignedBoundingBox::min, &AxisAlignedBoundingBox::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(planes, [&corners](const auto & frustumPlane) {
+		return (std::ranges::all_of(corners, [&frustumPlane](const auto & corner) {
+			return glm::dot(frustumPlane, corner) < 0.F;
+		}));
+	});
+}
+
 void
 Frustum::updateCache()
 {
diff --git a/gfx/frustum.h b/gfx/frustum.h
index 46f4108..5ee7d2c 100644
--- a/gfx/frustum.h
+++ b/gfx/frustum.h
@@ -4,6 +4,8 @@
 #include <array>
 #include <glm/mat4x4.hpp>
 
+class AxisAlignedBoundingBox;
+
 class Frustum {
 public:
 	Frustum(const GlobalPosition3D & pos, const glm::mat4 & view, const glm::mat4 & projection);
@@ -28,6 +30,8 @@ public:
 
 	void updateView(const glm::mat4 & view);
 
+	[[nodiscard]] bool contains(const AxisAlignedBoundingBox &) const;
+
 protected:
 	static constexpr size_t FACES = 6;
 	void updateCache();