Index: trunk/src/engine/particle_engine.cc
===================================================================
--- trunk/src/engine/particle_engine.cc	(revision 529)
+++ trunk/src/engine/particle_engine.cc	(revision 532)
@@ -196,5 +196,5 @@
 	datap->plane_normal = normalize_safe( datap->plane_normal, vec3(0.0f,1.0f,0.0f) );
 	datap->bounce       = table->get<float>("bounce", 0.0f );
-	datap->distance     = -math::dot( datap->plane_normal, datap->plane_point ) / sqrt( math::dot( datap->plane_normal, datap->plane_normal ) );
+	datap->distance     = -math::dot( datap->plane_normal, datap->plane_point ) / math::sqrt( math::dot( datap->plane_normal, datap->plane_normal ) );
 	return true;
 }