From e247b118619e15fe373a4f8e604542e98299accc Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Fri, 23 Jan 2004 21:47:39 +0000
Subject: [PATCH] Added proper handling of the rotation of billboards about an
 artbitary axis. Note, this code while mathermatically is not optimal, and
 will need to reviewed in the future to optimize it.

---
 src/osg/Billboard.cpp | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/osg/Billboard.cpp b/src/osg/Billboard.cpp
index 5b0e88213..4725698c8 100644
--- a/src/osg/Billboard.cpp
+++ b/src/osg/Billboard.cpp
@@ -73,7 +73,7 @@ void Billboard::updateCache()
     else _cachedMode = _mode;
     
     _side = _axis^_normal;
-    _side.normalize();    
+    _side.normalize();   
 }
 
 bool Billboard::addDrawable(Drawable *gset)
@@ -140,8 +140,6 @@ bool Billboard::computeMatrix(Matrix& modelview, const Vec3& eye_local, const Ve
             float ev_length = ev.length();
             if (ev_length>0.0f)
             {
-
-                matrix.makeIdentity();
                 //float rotation_zrotation_z = atan2f(ev.x(),ev.y());
                 //mat.makeRotate(inRadians(rotation_z),0.0f,0.0f,1.0f);
                 float inv = 1.0f/ev_length;
@@ -160,8 +158,6 @@ bool Billboard::computeMatrix(Matrix& modelview, const Vec3& eye_local, const Ve
             float ev_length = ev.length();
             if (ev_length>0.0f)
             {
-
-                matrix.makeIdentity();
                 //float rotation_zrotation_z = atan2f(ev.x(),ev.y());
                 //mat.makeRotate(inRadians(rotation_z),0.0f,0.0f,1.0f);
                 float inv = 1.0f/ev_length;
@@ -181,7 +177,6 @@ bool Billboard::computeMatrix(Matrix& modelview, const Vec3& eye_local, const Ve
             if (ev_length>0.0f)
             {
 
-                matrix.makeIdentity();
                 //float rotation_zrotation_z = atan2f(ev.x(),ev.y());
                 //mat.makeRotate(inRadians(rotation_z),0.0f,0.0f,1.0f);
                 float inv = 1.0f/ev_length;
@@ -195,6 +190,13 @@ bool Billboard::computeMatrix(Matrix& modelview, const Vec3& eye_local, const Ve
             break;
         }
         case(AXIAL_ROT): // need to implement 
+        {
+            float ev_side = ev*_side;
+            float ev_normal = ev*_normal;
+            float rotation = atan2f(ev_side,ev_normal);
+            matrix.makeRotate(rotation,_axis);
+            break;
+        }
         case(POINT_ROT_WORLD):
         case(POINT_ROT_EYE):
         {