--- vtkVolumeProVP1000Mapper.cxx	Wed May 19 10:47:51 2004
+++ vtkVolumeProVP1000Mapper.cxx.new	Fri Aug 27 21:43:47 2004
@@ -33,7 +33,11 @@
 #include "vtkVolumeProperty.h"
 
 #include <stdio.h>
+#include <string.h>
 #include <math.h>
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
 
 vtkCxxRevisionMacro(vtkVolumeProVP1000Mapper, "$Revision: 1.27 $");
 
@@ -217,12 +221,6 @@
   ren->GetActiveCamera()->GetFocalPoint( focalPointVTK );
   ren->GetActiveCamera()->GetViewUp( viewUpVTK );
 
-  // make sure we are in parallel mode
-  if (!ren->GetActiveCamera()->GetParallelProjection())
-    {
-    vtkWarningMacro("The Volume Pro VP1000 does not support perspective projection and the camera is currently not in ParallelProjection mode.");
-    }
-
   // Create the three vectors we need to do the lookat
   VLIVector3D positionVLI ( positionVTK );
   VLIVector3D focalPointVLI ( focalPointVTK );
@@ -233,20 +231,61 @@
                                               viewUpVLI );
   status = this->Context->GetCamera().SetViewMatrix( viewMatrixVLI );
 
-  double clippingRange[2], parallelScale;
+  int setupParallel = ren->GetActiveCamera()->GetParallelProjection();
+  double clippingRange[2];
   double aspect[2];
   ren->GetActiveCamera()->GetClippingRange(clippingRange);
   ren->GetAspect(aspect);
-  parallelScale = ren->GetActiveCamera()->GetParallelScale();
 
-  VLIMatrix projectionMatrixVLI = VLIMatrix::Ortho(-parallelScale*aspect[0],
-                                                   parallelScale*aspect[0],
-                                                   -parallelScale,
-                                                   parallelScale,
-                                                   clippingRange[0],
-                                                   clippingRange[1]);
+  if (! setupParallel)
+    {
+    // VLI versions prior to 3.1.0 do not support perspective projection
+    // and later versions only do so if the library has advanced features
+    // enabled.  Can test for whether or not advanced features are enabled
+    // by looking for an AF in the library version string.  If the system
+    // does not support perspective projection, force parallel projection.
+    if (strstr(VLIConfiguration::GetVersionString(VLIConfiguration::kVLIVersion), "AF") == 0)
+      {
+      setupParallel = 1;
+      vtkWarningMacro("The Volume Pro VP1000 does not support perspective projection and the camera is currently not in ParallelProjection mode.");
+      }
+    }
+
+  if (! setupParallel)
+    {
+    double viewAngleRadians = ren->GetActiveCamera()->GetViewAngle() *
+	M_PI / 180.0;
+
+    // Manually construct the matrix to avoid using VLIMatrix::Perspective()
+    // which is not available in VLI versions prior to 3.1.0.
+    VLIMatrix projectionMatrixVLI;
+    double f = cos(0.5 * viewAngleRadians) / sin(0.5 * viewAngleRadians);
+
+    projectionMatrixVLI[0][0] = f / aspect[0];
+    projectionMatrixVLI[1][1] = f;
+    projectionMatrixVLI[2][2] = (clippingRange[1] + clippingRange[0]) /
+	(clippingRange[0] - clippingRange[1]);
+    projectionMatrixVLI[2][3] = 2.0 * clippingRange[1] * clippingRange[0] /
+	(clippingRange[0] - clippingRange[1]);
+    projectionMatrixVLI[3][2] = -1.0;
+    projectionMatrixVLI[3][3] = 0.0;
+
+    status = this->Context->GetCamera().SetProjectionMatrix( projectionMatrixVLI );
+    }
+
+  if (setupParallel)
+    {
+    double parallelScale = ren->GetActiveCamera()->GetParallelScale();
+
+    VLIMatrix projectionMatrixVLI = VLIMatrix::Ortho(-parallelScale*aspect[0],
+						     parallelScale*aspect[0],
+						     -parallelScale,
+						     parallelScale,
+						     clippingRange[0],
+						     clippingRange[1]);
   
-  status = this->Context->GetCamera().SetProjectionMatrix( projectionMatrixVLI );
+    status = this->Context->GetCamera().SetProjectionMatrix( projectionMatrixVLI );
+    }
 
   if ( status != kVLIOK )
     {