From e66372a13770905c4095a0659ceb5f4ddee0d2a2 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Wed, 15 May 2002 19:58:04 +0000
Subject: [PATCH] Fixed problem with orhographic projections due to a bug in
 CullVisitor where it automatically resets the near and far to the values
 calculated during cull traversal.  The maths for converting the computed far
 and near into clip coordinates was wrong, fixed this and the problem goes
 away.

---
 src/osgUtil/CullVisitor.cpp          | 10 +++++-----
 src/osgUtil/TrackballManipulator.cpp |  7 +++++++
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/osgUtil/CullVisitor.cpp b/src/osgUtil/CullVisitor.cpp
index 86d3a8993..70c6722c3 100644
--- a/src/osgUtil/CullVisitor.cpp
+++ b/src/osgUtil/CullVisitor.cpp
@@ -218,16 +218,16 @@ void CullVisitor::popProjectionMatrix()
         // so it doesn't cull them out.
         osg::Matrix& projection = *_projectionStack.back();
 
-        double desired_znear = _computed_znear*0.95;
-        double desired_zfar = _computed_zfar*1.05;
+        double desired_znear = _computed_znear;
+        double desired_zfar = _computed_zfar;
 
         double min_near_plane = _computed_zfar*0.0005f;
         if (desired_znear<min_near_plane) desired_znear=min_near_plane;
 
-        double trans_near_plane = (-desired_znear*projection(0,2)-desired_znear*projection(1,2)-desired_znear*projection(2,2)+projection(3,2))/(-desired_znear*projection(2,3));
-        double trans_far_plane = (-desired_zfar*projection(0,2)-desired_zfar*projection(1,2)-desired_zfar*projection(2,2)+projection(3,2))/(-desired_zfar*projection(2,3));
+        double trans_near_plane = (-desired_znear*projection(2,2)+projection(3,2))/(-desired_znear*projection(2,3)+projection(3,3));
+        double trans_far_plane = (-desired_zfar*projection(2,2)+projection(3,2))/(-desired_zfar*projection(2,3)+projection(3,3));
 
-        double ratio = fabs(2.0f/(trans_near_plane-trans_far_plane));
+        double ratio = fabs(2.0f/(trans_near_plane-trans_far_plane))*0.95;
         double center = -(trans_near_plane+trans_far_plane)/2.0f;
 
         projection.postMult(osg::Matrix(1.0f,0.0f,0.0f,0.0f,
diff --git a/src/osgUtil/TrackballManipulator.cpp b/src/osgUtil/TrackballManipulator.cpp
index d2f88e988..622aff526 100644
--- a/src/osgUtil/TrackballManipulator.cpp
+++ b/src/osgUtil/TrackballManipulator.cpp
@@ -143,6 +143,13 @@ bool TrackballManipulator::handle(const GUIEventAdapter& ea,GUIActionAdapter& us
                 _camera->setFusionDistanceRatio(_camera->getFusionDistanceRatio()/1.25f);
                 return true;
             }
+// this is quick hack to test out othographic projection.            
+//             else if (ea.getKey()=='O')
+//             {
+//                 float dist = _camera->getLookDistance();
+//                 _camera->setOrtho(-dist,dist,-dist,dist,-dist,dist);
+//                 return true;
+//             }
             return false;
         case(GUIEventAdapter::FRAME):
             _camera->setFusionDistanceMode(osg::Camera::PROPORTIONAL_TO_LOOK_DISTANCE);