From 579c45cc66aa5e68a8a9f9ac44051da450c6225d Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan.goodliffe@octal.co.uk>
Date: Tue, 13 Dec 2022 12:09:29 +0000
Subject: Calculate an accurate up vector for the camera

---
 gfx/gl/camera.cpp |  7 +++++++
 gfx/gl/camera.h   | 20 ++++++++++++++++----
 2 files changed, 23 insertions(+), 4 deletions(-)

(limited to 'gfx/gl')

diff --git a/gfx/gl/camera.cpp b/gfx/gl/camera.cpp
index fadbfd7..69cfe35 100644
--- a/gfx/gl/camera.cpp
+++ b/gfx/gl/camera.cpp
@@ -25,3 +25,10 @@ Camera::updateView()
 	viewProjection = projection * view;
 	inverseViewProjection = glm::inverse(viewProjection);
 }
+
+glm::vec3
+Camera::upFromForward(const glm::vec3 & forward)
+{
+	const auto right = glm::cross(forward, ::down);
+	return glm::cross(forward, right);
+}
diff --git a/gfx/gl/camera.h b/gfx/gl/camera.h
index 3182969..2d937a0 100644
--- a/gfx/gl/camera.h
+++ b/gfx/gl/camera.h
@@ -24,18 +24,28 @@ public:
 	void
 	setForward(const glm::vec3 & f)
 	{
-		forward = f;
-		updateView();
+		setForward(f, upFromForward(f));
 	}
 	void
-	setView(const glm::vec3 & p, const glm::vec3 & f, const glm::vec3 & u = ::up)
+	setForward(const glm::vec3 & f, const glm::vec3 & u)
 	{
-		position = p;
 		forward = f;
 		up = u;
 		updateView();
 	}
 	void
+	setView(const glm::vec3 & p, const glm::vec3 & f)
+	{
+		position = p;
+		setForward(f);
+	}
+	void
+	setView(const glm::vec3 & p, const glm::vec3 & f, const glm::vec3 & u)
+	{
+		position = p;
+		setView(f, u);
+	}
+	void
 	lookAt(const glm::vec3 & target)
 	{
 		setForward(glm::normalize(target - position));
@@ -51,6 +61,8 @@ public:
 		return position;
 	}
 
+	static glm::vec3 upFromForward(const glm::vec3 & forward);
+
 private:
 	void updateView();
 
-- 
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