diff --git a/Imaging/Core/vtkRTAnalyticSource.cxx b/Imaging/Core/vtkRTAnalyticSource.cxx
index eb61d3b..7e0d137 100644
--- a/Imaging/Core/vtkRTAnalyticSource.cxx
+++ b/Imaging/Core/vtkRTAnalyticSource.cxx
@@ -200,10 +200,18 @@ void vtkRTAnalyticSource::ExecuteDataWithInformation(vtkDataObject *vtkNotUsed(o
   target = static_cast<unsigned long>((maxZ+1)*(maxY+1)/50.0);
   target++;
 
-  // Loop through output pixels
+  //
+  // Lets invert this divide so we can use a multiply.  Faster.
+  // Also, note that we move the calculation of the cosine for Z and Y
+  //   as high in the for() loops as possible.
+  //
   temp2 = 1.0 / (2.0 * this->StandardDeviation * this->StandardDeviation);
 
   double x, y, z;
+  double cosZtmp, sinYtmp;
+
+  // Loop through output pixels
+  //
   for (idxZ = 0; idxZ <= maxZ; idxZ++)
     {
     if (idxZ % this->SubsampleRate)
@@ -216,6 +224,8 @@ void vtkRTAnalyticSource::ExecuteDataWithInformation(vtkDataObject *vtkNotUsed(o
       z /= (whlExt[5] - whlExt[4]);
       }
     zContrib = z * z;
+    cosZtmp = this->ZMag*cos(this->ZFreq*z);
+
     for (idxY = 0; !this->AbortExecute && idxY <= maxY; idxY++)
       {
       if (idxY % this->SubsampleRate)
@@ -233,25 +243,112 @@ void vtkRTAnalyticSource::ExecuteDataWithInformation(vtkDataObject *vtkNotUsed(o
         y /= (whlExt[3] - whlExt[2]);
         }
       yContrib = y * y;
-      for (idxX = 0; idxX <= maxX; idxX++)
+      sinYtmp = this->YMag*sin(this->YFreq*y);
+
+      if (whlExt[1] > whlExt[0])
+        {
+        double invDiffExt = 1.0 / (whlExt[1] - whlExt[0]);
+        //
+        // Lets move the if test for Subsample rate out of the for loop.
+        //   This makes two (almost) similar for loops.  
+        //
+        if (this->SubsampleRate == 1) 
+          {
+          for (idxX = 0; idxX <= maxX; idxX++)
+            {
+            // Pixel operation
+            x = this->Center[0] - (idxX + newOutExt[0]);
+            x *= invDiffExt;
+            sum = zContrib + yContrib;
+            sum = sum + (x * x);
+  
+            //*outPtr = this->Maximum * exp(-sum * temp2)
+            //  + this->XMag*sin(this->XFreq*x)
+            //  + this->YMag*sin(this->YFreq*y)
+            //  + this->ZMag*cos(this->ZFreq*z);
+            
+            *outPtr = this->Maximum * exp(-sum * temp2)
+              + this->XMag*sin((float)(this->XFreq*x))
+              + sinYtmp
+              + cosZtmp;
+            outPtr++;
+            }
+          }
+        else
+          {
+          for (idxX = 0; idxX <= maxX; idxX++)
+            {
+            if (idxX % this->SubsampleRate)
+              {
+              continue;
+              }
+            // Pixel operation
+            x = this->Center[0] - (idxX + newOutExt[0]);
+            x *= invDiffExt;
+            sum = zContrib + yContrib;
+            sum = sum + (x * x);
+
+            //*outPtr = this->Maximum * exp(-sum * temp2)
+            //  + this->XMag*sin(this->XFreq*x)
+            //  + this->YMag*sin(this->YFreq*y)
+            //  + this->ZMag*cos(this->ZFreq*z);
+            
+            *outPtr = this->Maximum * exp(-sum * temp2)
+              + this->XMag*sin((float)(this->XFreq*x))
+              + sinYtmp
+              + cosZtmp;
+            outPtr++;
+            }
+          }
+        } 
+      else
         {
-        if (idxX % this->SubsampleRate)
+        if (this->SubsampleRate == 1) 
           {
-          continue;
+          for (idxX = 0; idxX <= maxX; idxX++)
+            {
+            // Pixel operation
+            x = this->Center[0] - (idxX + newOutExt[0]);
+            sum = zContrib + yContrib;
+            sum = sum + (x * x);
+  
+            //*outPtr = this->Maximum * exp(-sum * temp2)
+            //  + this->XMag*sin(this->XFreq*x)
+            //  + this->YMag*sin(this->YFreq*y)
+            //  + this->ZMag*cos(this->ZFreq*z);
+            
+            *outPtr = this->Maximum * exp(-sum * temp2)
+              + this->XMag*sin((float)(this->XFreq*x))
+              + sinYtmp
+              + cosZtmp;
+            outPtr++;
+            }
           }
-        // Pixel operation
-        sum = zContrib + yContrib;
-        x = this->Center[0] - (idxX + newOutExt[0]);
-        if (whlExt[1] > whlExt[0])
+        else
           {
-          x /= (whlExt[1] - whlExt[0]);
+          for (idxX = 0; idxX <= maxX; idxX++)
+            {
+            if (idxX % this->SubsampleRate)
+              {
+              continue;
+              }
+            // Pixel operation
+            x = this->Center[0] - (idxX + newOutExt[0]);
+            sum = zContrib + yContrib;
+            sum = sum + (x * x);
+
+            //*outPtr = this->Maximum * exp(-sum * temp2)
+            //  + this->XMag*sin(this->XFreq*x)
+            //  + this->YMag*sin(this->YFreq*y)
+            //  + this->ZMag*cos(this->ZFreq*z);
+          
+            *outPtr = this->Maximum * exp(-sum * temp2)
+              + this->XMag*sin((float)(this->XFreq*x))
+              + sinYtmp
+              + cosZtmp;
+            outPtr++;
+            }
           }
-        sum = sum + (x * x);
-        *outPtr = this->Maximum * exp(-sum * temp2)
-          + this->XMag*sin(this->XFreq*x)
-          + this->YMag*sin(this->YFreq*y)
-          + this->ZMag*cos(this->ZFreq*z);
-        outPtr++;
         }
       outPtr += outIncY;
       }

From ba0a6dc287a4416a6e71ef79e91eeb2f7783e140 Mon Sep 17 00:00:00 2001
From: W Alan Scott <wascott@sandia.gov>
Date: Wed, 22 Jul 2015 13:31:53 -0400
Subject: [PATCH] Performance improvements to vtkRTAnalyticSource.

---
 Imaging/Core/vtkRTAnalyticSource.cxx | 33 +++++++++++++++------------------
 1 file changed, 15 insertions(+), 18 deletions(-)

diff --git a/Imaging/Core/vtkRTAnalyticSource.cxx b/Imaging/Core/vtkRTAnalyticSource.cxx
index eb61d3b..f3bd8d7 100644
--- a/Imaging/Core/vtkRTAnalyticSource.cxx
+++ b/Imaging/Core/vtkRTAnalyticSource.cxx
@@ -204,21 +204,22 @@ void vtkRTAnalyticSource::ExecuteDataWithInformation(vtkDataObject *vtkNotUsed(o
   temp2 = 1.0 / (2.0 * this->StandardDeviation * this->StandardDeviation);
 
   double x, y, z;
+  const double xscale = (whlExt[1] > whlExt[0])? (1.0/(whlExt[1] - whlExt[0])) : 1.0;
+  const double yscale = (whlExt[3] > whlExt[2])? (1.0/(whlExt[3] - whlExt[2])) : 1.0;
+  const double zscale = (whlExt[5] > whlExt[4])? (1.0/(whlExt[5] - whlExt[4])) : 1.0;
   for (idxZ = 0; idxZ <= maxZ; idxZ++)
     {
-    if (idxZ % this->SubsampleRate)
+    if ((this->SubsampleRate > 1) && (idxZ % this->SubsampleRate))
       {
       continue;
       }
     z = this->Center[2] - (idxZ + newOutExt[4]);
-    if (whlExt[5] > whlExt[4])
-      {
-      z /= (whlExt[5] - whlExt[4]);
-      }
+    z *= zscale;
     zContrib = z * z;
+    const float zfactor = static_cast<float>(this->ZMag*cos(this->ZFreq*z));
     for (idxY = 0; !this->AbortExecute && idxY <= maxY; idxY++)
       {
-      if (idxY % this->SubsampleRate)
+      if ((this->SubsampleRate > 1) && (idxY % this->SubsampleRate))
         {
         continue;
         }
@@ -228,29 +229,25 @@ void vtkRTAnalyticSource::ExecuteDataWithInformation(vtkDataObject *vtkNotUsed(o
         }
       count++;
       y = this->Center[1] - (idxY + newOutExt[2]);
-      if (whlExt[3] > whlExt[2])
-        {
-        y /= (whlExt[3] - whlExt[2]);
-        }
+      y *= yscale;
       yContrib = y * y;
+      const float yfactor = static_cast<float>(this->YMag*sin(this->YFreq*y));
       for (idxX = 0; idxX <= maxX; idxX++)
         {
-        if (idxX % this->SubsampleRate)
+        if ((this->SubsampleRate > 1) && (idxX % this->SubsampleRate))
           {
           continue;
           }
         // Pixel operation
         sum = zContrib + yContrib;
         x = this->Center[0] - (idxX + newOutExt[0]);
-        if (whlExt[1] > whlExt[0])
-          {
-          x /= (whlExt[1] - whlExt[0]);
-          }
+        x *= xscale;
         sum = sum + (x * x);
+        const float xfactor = static_cast<float>(this->XMag*sin(this->XFreq*x));
         *outPtr = this->Maximum * exp(-sum * temp2)
-          + this->XMag*sin(this->XFreq*x)
-          + this->YMag*sin(this->YFreq*y)
-          + this->ZMag*cos(this->ZFreq*z);
+          + xfactor /*this->XMag*sin(this->XFreq*x)*/
+          + yfactor /*this->YMag*sin(this->YFreq*y)*/
+          + zfactor /*this->ZMag*cos(this->ZFreq*z)*/;
         outPtr++;
         }
       outPtr += outIncY;
-- 
1.9.1