From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 5 Nov 2016 22:10:59 +0000 (+0200)
Subject: Properly compute frustum culling for orthographic cameras
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=d16abe533233dc15810fe6bdf4a873d36eefc5dc;p=libs%2Fgl.git

Properly compute frustum culling for orthographic cameras

It's still incorrect for skewed frustums but I'll fix that later.
---

diff --git a/source/camera.h b/source/camera.h
index 44d3bf33..59cbaae3 100644
--- a/source/camera.h
+++ b/source/camera.h
@@ -36,6 +36,9 @@ public:
 	void set_frustum_axis(float, float);
 	void set_frustum_rotation(const Geometry::Angle<float> &);
 	const Geometry::Angle<float> &get_field_of_view() const { return fov; }
+	bool is_orthographic() const { return fov==Geometry::Angle<float>::zero(); }
+	float get_orthographic_width() const { return height*aspect; }
+	float get_orthographic_height() const { return height; }
 	float get_aspect() const { return aspect; }
 	float get_near_clip() const { return clip_near; }
 	float get_far_clip() const { return clip_far; }
diff --git a/source/scene.cpp b/source/scene.cpp
index ad9dcd15..1625ca32 100644
--- a/source/scene.cpp
+++ b/source/scene.cpp
@@ -29,15 +29,28 @@ bool Scene::setup_frustum(const Renderer &renderer) const
 
 	culling_matrix = renderer.get_matrix();
 
-	float y = tan(camera->get_field_of_view()/2.0f);
-	float s = sqrt(y*y+1);
-	frustum_edges[0] = Vector4(0, 1/s, y/s, 0);
-	frustum_edges[1] = Vector4(0, -1/s, y/s, 0);
-
-	float x = y*camera->get_aspect();
-	s = sqrt(x*x+1);
-	frustum_edges[2] = Vector4(1/s, 0, x/s, 0);
-	frustum_edges[3] = Vector4(-1/s, 0, x/s, 0);
+	if(camera->is_orthographic())
+	{
+		float h = camera->get_orthographic_height();
+		frustum_edges[0] = Vector4(0, 1, 0, -h);
+		frustum_edges[1] = Vector4(0, -1, 0, -h);
+
+		float w = camera->get_orthographic_width();
+		frustum_edges[2] = Vector4(1, 0, 0, -w);
+		frustum_edges[3] = Vector4(-1, 0, 0, -w);
+	}
+	else
+	{
+		float y = tan(camera->get_field_of_view()/2.0f);
+		float s = sqrt(y*y+1);
+		frustum_edges[0] = Vector4(0, 1/s, y/s, 0);
+		frustum_edges[1] = Vector4(0, -1/s, y/s, 0);
+
+		float x = y*camera->get_aspect();
+		s = sqrt(x*x+1);
+		frustum_edges[2] = Vector4(1/s, 0, x/s, 0);
+		frustum_edges[3] = Vector4(-1/s, 0, x/s, 0);
+	}
 
 	frustum_edges[4] = Vector4(0, 0, -1, -camera->get_far_clip());
 	frustum_edges[5] = Vector4(0, 0, 1, camera->get_near_clip());