From 4e10d57f83f719e02005fe41e70fe1a4721a9439 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Wed, 5 Mar 2025 23:52:18 +0000
Subject: Split core view definition out of Camera into Frustum

---
 gfx/frustum.cpp | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 gfx/frustum.cpp

(limited to 'gfx/frustum.cpp')

diff --git a/gfx/frustum.cpp b/gfx/frustum.cpp
new file mode 100644
index 0000000..9e046f6
--- /dev/null
+++ b/gfx/frustum.cpp
@@ -0,0 +1,30 @@
+#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 glm::mat4 & view, const glm::mat4 & projection) :
+	view {view}, projection {projection}, viewProjection {}, inverseViewProjection {}, planes {}
+{
+	updateCache();
+}
+
+void
+Frustum::updateView(const glm::mat4 & newView)
+{
+	view = newView;
+	updateCache();
+}
+
+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);
+	});
+}
-- 
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