From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 28 Nov 2016 00:20:20 +0000 (+0200)
Subject: Properly scale the the bounding sphere for frustum culling
X-Git-Url: http://git.tdb.fi/?p=libs%2Fgl.git;a=commitdiff_plain;h=380e636ddeb5811cb5d87800c445638246269b62;hp=d1e3975c163694d7bca6417463462be950019e5e

Properly scale the the bounding sphere for frustum culling

The original radius must be squared too.  Also, negative distances mean
the sphere is inside the frustum and should not be culled.
---

diff --git a/source/scene.cpp b/source/scene.cpp
index 6c3d2910..b8a74b59 100644
--- a/source/scene.cpp
+++ b/source/scene.cpp
@@ -66,13 +66,13 @@ bool Scene::frustum_cull(const Renderable &renderable) const
 		return false;
 
 	Vector4 center = culling_matrix*(*matrix*compose(bsphere->get_center(), 1.0f));
-	Vector4 x_axis = *matrix*Vector4(1.0f, 0.0f, 0.0f, 0.0f);
-	float radius_sq = bsphere->get_radius()*inner_product(x_axis, x_axis);
+	Vector4 x_axis = *matrix*Vector4(bsphere->get_radius(), 0.0f, 0.0f, 0.0f);
+	float radius_sq = inner_product(x_axis, x_axis);
 
 	for(unsigned i=0; i<6; ++i)
 	{
 		float distance = inner_product(center, frustum_edges[i]);
-		if(distance*distance>radius_sq)
+		if(distance>0 && distance*distance>radius_sq)
 			return true;
 	}