[vtk-developers] vtkVoxelModeller converted from BIT to INT

[Bill Lorensen]

Perhaps vtkVoxelModeller should have a new method;
SetOutputScalarTypeToxxx where the default would be Bit. Then it might
be a more useful class, It should also probably have
SetForegroundValue and SetBackgroundValue methods.

Bill

On Mon, Mar 15, 2010 at 10:20 AM, David Doria <daviddoria+vtk at gmail.com> wrote:
> On Mon, Mar 15, 2010 at 11:17 AM, Will Schroeder
> <will.schroeder at kitware.com> wrote:
>>
>> Hi David-
>> I think we have to approach this in a series of steps, we may not be able
>> to correctly solve the VTK_BIT problem immediately, but do something quick
>> with an eye to fixing it longer term.
>> One option: since the writer doesn't work now let's do something quickly,
>> documenting the fact (e.g. bug tracker, etc.) that long term we need to
>> improve the support for VTK_BIT. (I would use VTK_UNSIGNED_CHAR myself which
>> is half the size of VTK_SHORT assuming it works.)
>> Another option (and I am shooting from the hip here) is to do the minimal
>> work in the reader/writer to get VTK_BIT "sort of" working meaning you may
>> have to perform temporary conversions to and from VTK_BIT to another type,
>> etc. which may cause temporary increases in memory.
>> I'm sure there are other opinions in the community about this...
>> Will
>
> I tested vtkVoxelModeller using VTK_UNSIGNED_CHAR and it worked fine. I
> added the file to the bug report:
> http://public.kitware.com/Bug/view.php?id=10414
> I dug through the writer code for a while.
> In vtkXMLWriter.cxx I changed:
> vtkXMLWriter::OffsetType vtkXMLWriter::GetWordTypeSize(int dataType)
> {
>   OffsetType size = 1;
>   switch (dataType)
>     {
>     vtkTemplateMacro(
>       size = vtkXMLWriterGetWordTypeSize(static_cast<VTK_TT*>(0))
>       );
>   case VTK_STRING:
>     return sizeof(vtkStdString::value_type);
>   //case VTK_BIT: //doesn't work for some reason
>   case 1: // VTK_BIT == 1
>     return sizeof(bool);
>   default:
>       { vtkWarningMacro("Unsupported data type: " << dataType); } break;
>     }
>   return size;
> }
> in vtkXMLDataElement.cxx I changed:
> int vtkXMLDataElement::GetWordTypeAttribute(const char* name, int& value)
> {
>   // These string values must match vtkXMLWriter::GetWordTypeName().
>   const char* v = this->GetAttribute(name);
>   if(!v)
>     {
>     vtkErrorMacro("Missing word type attribute \"" << name << "\".");
>     return 0;
>     }
>   else if(strcmp(v, "Bit") == 0)
>     {
>     value = VTK_BIT;
>     return 1;
>     }
> It seems to write the file without a problem now. However, when I try to
> read it, in vtkXMLDataReader.cxx
> template <class iterT>
> int vtkXMLDataReaderReadArrayValues(vtkXMLDataElement* da,
>   vtkXMLDataParser* xmlparser, vtkIdType arrayIndex,
>   iterT* iter, vtkIdType startIndex, vtkIdType numValues)
> {
>   if (!iter)
>     {
>     return 0;
>     }
>   vtkAbstractArray* array = iter->GetArray();
> 'array' is null so then the code crashes. Maybe this could be a starting
> point for the next brave person?
> Thanks,
>
> David
>