Index: Rendering/vtkRenderWindow.cxx
===================================================================
RCS file: /cvsroot/VTK/VTK/Rendering/vtkRenderWindow.cxx,v
retrieving revision 1.150
diff -u -r1.150 vtkRenderWindow.cxx
--- Rendering/vtkRenderWindow.cxx	26 Oct 2006 21:36:55 -0000	1.150
+++ Rendering/vtkRenderWindow.cxx	14 May 2007 13:51:25 -0000
@@ -23,6 +23,8 @@
 #include "vtkRendererCollection.h"
 #include "vtkTransform.h"
 
+#include <math.h>
+
 vtkCxxRevisionMacro(vtkRenderWindow, "$Revision: 1.150 $");
 
 //----------------------------------------------------------------------------
@@ -427,6 +429,68 @@
     double origfocus[4];
     double worldOffset[3];
 
+    double *x_offsets;
+    double *y_offsets;
+
+    int N;
+    double x_offset, y_offset, offset_step;
+    double jitter_max;
+    int i, j;
+
+    // Pre-generate jittered camera offsets
+
+    x_offsets = new double[this->AAFrames];
+    y_offsets = new double[this->AAFrames];
+
+    N = int(sqrt(this->AAFrames));
+    if (N*N == this->AAFrames)
+    {
+        // N*N samples requested, use jittered stratified sampling.
+        // Generate N*N regurlarly spaced samples covering the center
+        // area of a pixel and jitter each of the sample locations 
+        // with a small amount. The final amount of camera offset is 
+        // in the range [-0.5, 0.5] for both X and Y, consistent with 
+        // VTK's current random offsets.
+        //
+        // Possible extension: pre-compute the sample locations once
+        // and store them in a static array, one per number of AA frames. 
+        // This way, each rendering using the same number of AA samples 
+        // will use the same sample locations (while still providing 
+        //  anti-aliasing). This will prevent the introduction of noise 
+        // in areas of the rendered image that do not differ between 
+        // successive frames.
+        
+        offset_step = 1.0 / N;
+        jitter_max = 0.5 * offset_step;					
+        
+        // jitter regularly spaced samples
+        
+        y_offset = -0.5 + 0.5*offset_step;
+        for (j = 0; j < N; j++)
+        {
+            x_offset = -0.5 + 0.5*offset_step;
+            
+            for (i = 0; i < N; i++)
+            {
+                x_offsets[j*N+i] = x_offset + jitter_max * vtkMath::Random(-1.0, 1.0);
+                y_offsets[j*N+i] = y_offset + jitter_max * vtkMath::Random(-1.0, 1.0);
+                
+                x_offset += offset_step;
+            }
+            
+            y_offset += offset_step;
+        }
+    }
+    else
+    {
+        // Simply generate this->AAFrames random offsets
+        for (i = 0; i < this->AAFrames; i++)
+        {
+            x_offsets[i] = vtkMath::Random(-0.5, 0.5);
+            y_offsets[i] = vtkMath::Random(-0.5, 0.5);
+        }
+    }
+    
     // get the size
     size = this->GetSize();
 
@@ -435,8 +499,8 @@
     for (i = 0; i < this->AAFrames; i++)
       {
       // jitter the cameras
-      offsets[0] = vtkMath::Random() - 0.5;
-      offsets[1] = vtkMath::Random() - 0.5;
+      offsets[0] = x_offsets[i];
+      offsets[1] = y_offsets[i];
 
       vtkCollectionSimpleIterator rsit;
       for (this->Renderers->InitTraversal(rsit);
@@ -531,6 +595,9 @@
         delete [] p3;
         }
       }
+      
+      delete [] x_offsets;
+      delete [] y_offsets;
     }
   else
     {