From 06bc35360da2e55b08fa0087e03c63e364ba3ebf Mon Sep 17 00:00:00 2001
From: Chris Brunner <github@chrisweb.us>
Date: Tue, 29 Jun 2010 22:47:44 +0000
Subject: [PATCH] Prevent trying to invert singular matrix

---
 panda/src/egg/eggGroup.cxx | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/panda/src/egg/eggGroup.cxx b/panda/src/egg/eggGroup.cxx
index 7c0a218ef5..7bdbc283cb 100644
--- a/panda/src/egg/eggGroup.cxx
+++ b/panda/src/egg/eggGroup.cxx
@@ -1236,12 +1236,20 @@ adjust_under() {
     // Our own transform also affects our node frame.
     _node_frame =
       new MatrixFrame(get_transform3d() * get_node_frame());
-    _node_frame_inv =
-      new MatrixFrame(invert(get_node_frame()));
+
+    // To prevent trying to invert a sigular matrix
+    LMatrix4d mat;
+    bool invert_ok = mat.invert_from(get_node_frame());
+    if (invert_ok) {
+      _node_frame_inv =
+        new MatrixFrame(invert(get_node_frame()));
+    }
+
     _vertex_to_node =
       new MatrixFrame(get_vertex_frame() * get_node_frame_inv());
     _node_to_vertex =
       new MatrixFrame(get_node_frame() * get_vertex_frame_inv());
+
   }
 
   if (is_instance_type()) {