From bb76f72831af73adb1b2deebd4b9235fa51fa7df Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sun, 11 Dec 2022 14:28:46 +0000
Subject: Cache view and viewProject matrices, update only on camera movement

---
 gfx/gl/camera.cpp | 14 ++++++++------
 gfx/gl/camera.h   | 13 ++++++++++++-
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/gfx/gl/camera.cpp b/gfx/gl/camera.cpp
index 1c46200..994d8ab 100644
--- a/gfx/gl/camera.cpp
+++ b/gfx/gl/camera.cpp
@@ -7,12 +7,7 @@ Camera::Camera(glm::vec3 pos, float fov, float aspect, float zNear, float zFar)
 	position {pos}, forward {::north}, up {::up}, fov {fov}, aspect {aspect}, near {zNear}, far {zFar},
 	projection {glm::perspective(fov, aspect, zNear, zFar)}
 {
-}
-
-glm::mat4
-Camera::getViewProjection() const
-{
-	return projection * glm::lookAt(position, position + forward, up);
+	updateView();
 }
 
 Ray
@@ -22,3 +17,10 @@ Camera::unProject(const glm::vec2 & mouse) const
 	return {position,
 			glm::normalize(glm::unProject(mouse ^ 1, glm::lookAt(::origin, forward, up), projection, screen))};
 }
+
+void
+Camera::updateView()
+{
+	view = glm::lookAt(position, position + forward, up);
+	viewProjection = projection * view;
+}
diff --git a/gfx/gl/camera.h b/gfx/gl/camera.h
index 5b9d339..94eb8fc 100644
--- a/gfx/gl/camera.h
+++ b/gfx/gl/camera.h
@@ -8,18 +8,24 @@ class Camera {
 public:
 	Camera(glm::vec3 pos, float fov, float aspect, float zNear, float zFar);
 
-	[[nodiscard]] glm::mat4 getViewProjection() const;
+	[[nodiscard]] glm::mat4
+	getViewProjection() const
+	{
+		return viewProjection;
+	}
 	[[nodiscard]] Ray unProject(const glm::vec2 &) const;
 
 	void
 	setPosition(const glm::vec3 & p)
 	{
 		position = p;
+		updateView();
 	}
 	void
 	setForward(const glm::vec3 & f)
 	{
 		forward = f;
+		updateView();
 	}
 	void
 	setView(const glm::vec3 & p, const glm::vec3 & f, const glm::vec3 & u = ::up)
@@ -27,6 +33,7 @@ public:
 		position = p;
 		forward = f;
 		up = u;
+		updateView();
 	}
 	void
 	lookAt(const glm::vec3 & target)
@@ -45,10 +52,14 @@ public:
 	}
 
 private:
+	void updateView();
+
 	glm::vec3 position;
 	glm::vec3 forward;
 	glm::vec3 up;
 
 	float fov, aspect, near, far;
 	glm::mat4 projection;
+	glm::mat4 view;
+	glm::mat4 viewProjection;
 };
-- 
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