From ba3971bb45b133d3f38b3f15db575af3fdf473a1 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Mon, 1 Mar 2010 13:00:04 +0000
Subject: [PATCH] Added a ShadowTechnique::computeOrthogonalVector(const
 osg::Vec3& direction) const method for helping compute an appropriate up
 vector to setViewMatrixAsLookAt(..) codes in osgShadow.  This will addresses
 previous issues that occured when look vectors co-incided with the hard coded
 up vectors.

---
 include/osgShadow/ShadowTechnique |  1 +
 src/osgShadow/ShadowMap.cpp       |  6 +++---
 src/osgShadow/ShadowTechnique.cpp | 13 +++++++++++++
 src/osgShadow/ShadowTexture.cpp   |  4 ++--
 4 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/include/osgShadow/ShadowTechnique b/include/osgShadow/ShadowTechnique
index 4c37c6e29..b67bc6e94 100644
--- a/include/osgShadow/ShadowTechnique
+++ b/include/osgShadow/ShadowTechnique
@@ -71,6 +71,7 @@ class OSGSHADOW_EXPORT ShadowTechnique : public osg::Object
                 ShadowTechnique* _shadowTechnique;
         };
 
+        osg::Vec3 computeOrthogonalVector(const osg::Vec3& direction) const;
 
         virtual ~ShadowTechnique();
         
diff --git a/src/osgShadow/ShadowMap.cpp b/src/osgShadow/ShadowMap.cpp
index 1ac885665..2dd7c280f 100644
--- a/src/osgShadow/ShadowMap.cpp
+++ b/src/osgShadow/ShadowMap.cpp
@@ -408,7 +408,7 @@ void ShadowMap::cull(osgUtil::CullVisitor& cv)
         {
             osg::Vec3 position(lightpos.x(), lightpos.y(), lightpos.z());
             _camera->setProjectionMatrixAsPerspective(fov, 1.0, 0.1, 1000.0);
-            _camera->setViewMatrixAsLookAt(position,position+lightDir,osg::Vec3(0.0f,1.0f,0.0f));
+            _camera->setViewMatrixAsLookAt(position,position+lightDir,computeOrthogonalVector(lightDir));
         }
         else
         {
@@ -435,7 +435,7 @@ void ShadowMap::cull(osgUtil::CullVisitor& cv)
                 float right = top;
 
                 _camera->setProjectionMatrixAsFrustum(-right,right,-top,top,znear,zfar);
-                _camera->setViewMatrixAsLookAt(position,bb.center(),osg::Vec3(0.0f,1.0f,0.0f));
+                _camera->setViewMatrixAsLookAt(position,bb.center(),computeOrthogonalVector(bb.center()-position));
             }
             else    // directional light
             {
@@ -457,7 +457,7 @@ void ShadowMap::cull(osgUtil::CullVisitor& cv)
                 float right = top;
 
                 _camera->setProjectionMatrixAsOrtho(-right, right, -top, top, znear, zfar);
-                _camera->setViewMatrixAsLookAt(position,bb.center(),osg::Vec3(0.0f,1.0f,0.0f));
+                _camera->setViewMatrixAsLookAt(position,bb.center(),computeOrthogonalVector(lightDir));
             }
 
 
diff --git a/src/osgShadow/ShadowTechnique.cpp b/src/osgShadow/ShadowTechnique.cpp
index 245edc5f9..a6f444402 100644
--- a/src/osgShadow/ShadowTechnique.cpp
+++ b/src/osgShadow/ShadowTechnique.cpp
@@ -14,6 +14,7 @@
 #include <osgShadow/ShadowTechnique>
 #include <osgShadow/ShadowedScene>
 #include <osg/Notify>
+#include <osg/io_utils>
 
 using namespace osgShadow;
 
@@ -92,3 +93,15 @@ void ShadowTechnique::traverse(osg::NodeVisitor& nv)
         _shadowedScene->osg::Group::traverse(nv);
     }
 }
+
+osg::Vec3 ShadowTechnique::computeOrthogonalVector(const osg::Vec3& direction) const
+{
+    float length = direction.length();
+    osg::Vec3 orthogonalVector = direction ^ osg::Vec3(0.0f, 1.0f, 0.0f);
+    if (orthogonalVector.normalize()<length*0.5f)
+    {
+        orthogonalVector = direction ^ osg::Vec3(0.0f, 0.0f, 1.0f);
+        orthogonalVector.normalize();
+    }
+    return orthogonalVector;
+}
\ No newline at end of file
diff --git a/src/osgShadow/ShadowTexture.cpp b/src/osgShadow/ShadowTexture.cpp
index ea3a932d5..3e43d784b 100644
--- a/src/osgShadow/ShadowTexture.cpp
+++ b/src/osgShadow/ShadowTexture.cpp
@@ -187,7 +187,7 @@ void ShadowTexture::cull(osgUtil::CullVisitor& cv)
 
             _camera->setReferenceFrame(osg::Camera::ABSOLUTE_RF);
             _camera->setProjectionMatrixAsFrustum(-right,right,-top,top,znear,zfar);
-            _camera->setViewMatrixAsLookAt(position,bb.center(),osg::Vec3(0.0f,1.0f,0.0f));
+            _camera->setViewMatrixAsLookAt(position,bb.center(),computeOrthogonalVector(bb.center()-position));
             
 
             // compute the matrix which takes a vertex from local coords into tex coords
@@ -221,7 +221,7 @@ void ShadowTexture::cull(osgUtil::CullVisitor& cv)
 
             _camera->setReferenceFrame(osg::Camera::ABSOLUTE_RF);
             _camera->setProjectionMatrixAsOrtho(-right, right, -top, top, znear, zfar);
-            _camera->setViewMatrixAsLookAt(position,bb.center(),osg::Vec3(0.0f,1.0f,0.0f));
+            _camera->setViewMatrixAsLookAt(position,bb.center(),computeOrthogonalVector(lightDir));
             
 
             // compute the matrix which takes a vertex from local coords into tex coords