From d0aceb54752078200bc75a96888ffaf7483678cb Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 7 Mar 2025 00:43:25 +0000
Subject: Add function to test if an AABB is visible in a frustum

---
 gfx/frustum.cpp | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

(limited to 'gfx/frustum.cpp')

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()
 {
-- 
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