Fix a couple minor issues with this mapper.

When arrays had really large negative values, table lookup crashed.

This commit also applies the default scale to the point sprite radius
only after the lookup in the table has happened.

Rendering/OpenGL2/vtkOpenGLPointGaussianMapper.cxx

@@ -50,12 +50,12 @@ public:
 
   bool UsingPoints;
   float *OpacityTable; // the table
-  float OpacityScale; // used for quick lookups
-  float OpacityOffset; // used for quick lookups
+  double OpacityScale; // used for quick lookups
+  double OpacityOffset; // used for quick lookups
 
   float *ScaleTable; // the table
-  float ScaleScale; // used for quick lookups
-  float ScaleOffset; // used for quick lookups
+  double ScaleScale; // used for quick lookups
+  double ScaleOffset; // used for quick lookups
 
 protected:
   vtkOpenGLPointGaussianMapperHelper();
@@ -341,15 +341,15 @@ void vtkOpenGLPointGaussianMapperHelperPackVBOTemplate3(
 
   if (opacities)
     {
-    float opacity = opacities->GetComponent(index,0);
+    double opacity = opacities->GetComponent(index,0);
     if (self->OpacityTable)
       {
-      float tindex = (opacity - self->OpacityOffset)*self->OpacityScale;
+      double tindex = (opacity - self->OpacityOffset)*self->OpacityScale;
       int itindex = static_cast<int>(tindex);
       opacity = (1.0 - tindex + itindex)*self->OpacityTable[itindex] +
         (tindex - itindex)*self->OpacityTable[itindex+1];
       }
-    rcolor.c[3] = opacity*255.0;
+    rcolor.c[3] = static_cast<float>(opacity*255.0);
     }
   else
     {
@@ -366,41 +366,41 @@ void vtkOpenGLPointGaussianMapperHelperPackVBOTemplate3(
     }
   else // otherwise splats
     {
-    float cos30 = cos(vtkMath::RadiansFromDegrees(30.0));
-
-    float radius = sizes ? sizes[index] : 1.0;
-    radius *= defaultScale;
+    double radius = sizes ? sizes[index] : 1.0;
     if (self->ScaleTable)
       {
-      float tindex = (radius - self->ScaleOffset)*self->ScaleScale;
+      double tindex = (radius - self->ScaleOffset)*self->ScaleScale;
       int itindex = static_cast<int>(tindex);
       radius = (1.0 - tindex + itindex)*self->ScaleTable[itindex] +
         (tindex - itindex)*self->ScaleTable[itindex+1];
       }
-
+    radius *= defaultScale;
     radius *= 3.0;
 
+    float radiusFloat = static_cast<float>(radius);
+    float cos30 = cos(vtkMath::RadiansFromDegrees(30.0));
+
     // Vertices
     *(it++) = pointPtr[0];
     *(it++) = pointPtr[1];
     *(it++) = pointPtr[2];
     *(it++) = rcolor.f;
-    *(it++) = -2.0f*radius*cos30;
-    *(it++) = -radius;
+    *(it++) = -2.0f*radiusFloat*cos30;
+    *(it++) = -radiusFloat;
 
     *(it++) = pointPtr[0];
     *(it++) = pointPtr[1];
     *(it++) = pointPtr[2];
     *(it++) = rcolor.f;
-    *(it++) = 2.0f*radius*cos30;
-    *(it++) = -radius;
+    *(it++) = 2.0f*radiusFloat*cos30;
+    *(it++) = -radiusFloat;
 
     *(it++) = pointPtr[0];
     *(it++) = pointPtr[1];
     *(it++) = pointPtr[2];
     *(it++) = rcolor.f;
     *(it++) = 0.0f;
-    *(it++) = 2.0f*radius;
+    *(it++) = 2.0f*radiusFloat;
     }
 }