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

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;
 	}