Add ability to adjust the table size

Rendering/Core/vtkPointGaussianMapper.cxx

@@ -30,6 +30,7 @@ vtkPointGaussianMapper::vtkPointGaussianMapper()
   this->ScalarOpacityFunction = 0;
   this->DefaultRadius = 1.0;
   this->Emissive = 1;
+  this->OpacityTableSize = 1024;
 }
 
 //-----------------------------------------------------------------------------
@@ -51,4 +52,5 @@ void vtkPointGaussianMapper::PrintSelf(ostream& os, vtkIndent indent)
   os << indent << "SplatShaderCode: " << (this->SplatShaderCode ? this->SplatShaderCode : "(none)") << "\n";
   os << indent << "Default Radius: " << this->DefaultRadius << "\n";
   os << indent << "Emissive: " << this->Emissive << "\n";
+  os << indent << "OpacityTableSize: " << this->OpacityTableSize << "\n";
 }

Rendering/Core/vtkPointGaussianMapper.h

@@ -57,6 +57,12 @@ public:
   void SetScalarOpacityFunction(vtkPiecewiseFunction *);
   vtkGetObjectMacro(ScalarOpacityFunction,vtkPiecewiseFunction);
 
+  // Description:
+  // The size of the table used in computing opacities, used when
+  // converting a vtkPiecewiseFunction to a table
+  vtkSetMacro(OpacityTableSize, int);
+  vtkGetMacro(OpacityTableSize, int);
+
   // Description:
   // Method to set the optional opacity array.  If specified this
   // array will be used to generate the opacity values.
@@ -86,6 +92,7 @@ protected:
 
   double DefaultRadius;
   int Emissive;
+  int OpacityTableSize;
 
 private:
   vtkPointGaussianMapper(const vtkPointGaussianMapper&); // Not implemented.

Rendering/OpenGL2/Testing/Cxx/TestPointGaussianMapperOpacity.cxx

@@ -92,6 +92,8 @@ int TestPointGaussianMapperOpacity(int argc, char *argv[])
   mapper->EmissiveOff();
 
   // show other shader examples
+  // the fragment that is rendered is that of a triangle
+  // large enough to encompass a circle of radius 3
   mapper->SetSplatShaderCode(
     // this first line keeps the default color opacity calcs
     // which you can then modify with additional code below

Rendering/OpenGL2/vtkOpenGLPointGaussianMapper.cxx

@@ -597,13 +597,14 @@ void vtkOpenGLPointGaussianMapperHelper::BuildOpacityArray(vtkPolyData *poly)
 
   // if a piecewise function was provided, use it to map the opacities
   vtkPiecewiseFunction *pwf = this->Owner->GetScalarOpacityFunction();
-  float table[1025];
+  int tableSize = this->Owner->GetOpacityTableSize();
+  float *table = new float[tableSize+1];
   if (pwf)
     {
     // build the interpolation table
-    pwf->GetTable(range[0],range[1],1024,table);
+    pwf->GetTable(range[0],range[1],tableSize,table);
     // duplicate the last value for bilinear interp edge case
-    table[1024] = table[1023];
+    table[tableSize] = table[tableSize-1];
     }
 
   vtkCellArray *verts = poly->GetVerts();
@@ -619,7 +620,7 @@ void vtkOpenGLPointGaussianMapperHelper::BuildOpacityArray(vtkPolyData *poly)
         float value = oda->GetComponent(indices[i],0);
         if (pwf)
           {
-          float index = 1023.0*(value - range[0])/(range[1] - range[0]);
+          float index = (tableSize - 1.0)*(value - range[0])/(range[1] - range[0]);
           int iindex = static_cast<int>(index);
           value = (1.0 - index + iindex)*table[iindex] + (index - iindex)*table[iindex+1];
           }
@@ -636,7 +637,7 @@ void vtkOpenGLPointGaussianMapperHelper::BuildOpacityArray(vtkPolyData *poly)
       float value = oda->GetComponent(i,0);
       if (pwf)
         {
-        float index = 1023.0*(value - range[0])/(range[1] - range[0]);
+        float index = (tableSize-1.0)*(value - range[0])/(range[1] - range[0]);
         int iindex = static_cast<int>(index);
         value = (1.0 - index + iindex)*table[iindex] + (index - iindex)*table[iindex+1];
         }
@@ -644,6 +645,8 @@ void vtkOpenGLPointGaussianMapperHelper::BuildOpacityArray(vtkPolyData *poly)
       count++;
       }
     }
+
+  delete [] table;
 }
 
 //-------------------------------------------------------------------------