[vtkusers] Problem with lookup table, mapper, and number of colors in 5.8

[David Gobbi]

Hi Riku,

The discrepancy probably has something to do with this:

mapper->InterpolateScalarsBeforeMappingOn();

This method defers the color mapping to OpenGL, so it
might vary in behavior between OpenGL implementations.

 - David


On Tue, Apr 5, 2011 at 5:08 AM, Riku <subs at collab.se> wrote:
> Hello,
>
> I am going to annoyingly bump this topic again, as I still have found
> no solution to the problem. Has anyone been able to reproduce the
> deviant behaviour I described? At present I would categorize it a big
> problem to the code, unless I made a blatantly obvious mistake.
>
> To summarize: plots rendered with the release head of VTK and osmesa
> do not honour the number of colours set in the lookup table.
>
> (The VTK file referenced in the test code below is from the VTK data directory.)
>
> Thank you,
>
> Riku
>
>
> On 21 February 2011 13:34, Riku <subs at collab.se> wrote:
>> Hello,
>>
>> So far no new input regarding my problem (see below), so I thought I'd
>> report some more on the problem and my recent findings. (Hoping
>> someone might have a lead on this.)
>>
>> I have attached two PNG images that highlight my present problem.
>>
>> It seems that the problem is in some way related to OSMesa and/or what
>> happens in VTK when that implementation is used. For my testing, I
>> have created four different builds for shared objects:
>>
>> vtk-5.6.1
>> vtk-5.6.1-osmesa
>> vtk-5.8
>> vtk-5.8-osmesa    <-- problem is here
>>
>> The CMake settings are the same for the four build, except for the
>> OSMesa settings. (VTK_OPENGL_HAS_OSMESA is true, VTK_USE_X
>> is false, OPENGL_gl_LIBRARY is set to the empty string.) For the
>> OSMesa builds, the resulting libraries have no dependencies on X
>> libraries or on libGL, only on libOSMesa.
>>
>> With the testing program (below), all is fine for the three first
>> cases. For vtk-5.8-osmesa the colors go "wild". Is this a bug in the
>> VTK code? I have started to review the code changes that I think are
>> involved, but have so far not found anything obviously useful.
>>
>> Still hoping for some leads! I am very thankful for any help, as I
>> need precisely my last case to work.
>>
>> Riku
>>
>>
>>
>> On 17 February 2011 12:49, Riku <subs at collab.se> wrote:
>>> Hello all,
>>>
>>> I have a weird problem using the VTK source code from the release head
>>> in git. The results differ consistently between VS2008 (Windows 7
>>> 64-bit) and gcc (Ubuntu 10.10).
>>>
>>> In the test program I set the number of table values (colors) in the
>>> lookup table to 10. In the rendered image this is reflected correctly
>>> by the scalar bar actor, but NOT by the sliced structured grid, but
>>> only when running the program on Linux. I get a higher number of
>>> colors than requested, but it seems different inputs give different
>>> results. I have not been able to understand the logic of the problem.
>>> The Windows compiled program behaves "well".
>>>
>>> My test program below reproduces the problem. Am I missing anything
>>> obvious? Can someone else reproduce the problem? (Is this an issue for
>>> the developers?)
>>>
>>> I have compiled the release head in different varieties, all with the
>>> same result.
>>>
>>> Thanks for any help!
>>>
>>> Riku
>>>
>>> --- Test code below ---
>>>
>>> #include "vtkSmartPointer.h"
>>> #include "vtkDataSetReader.h"
>>> #include "vtkPlane.h"
>>> #include "vtkCutter.h"
>>> #include "vtkLookupTable.h"
>>> #include "vtkDataSetMapper.h"
>>> #include "vtkActor.h"
>>> #include "vtkScalarBarActor.h"
>>> #include "vtkRenderer.h"
>>> #include "vtkRenderWindow.h"
>>> #include "vtkWindowToImageFilter.h"
>>> #include "vtkPNGWriter.h"
>>>
>>> #define VTK_CREATE(type, var) vtkSmartPointer<type> var =
>>> vtkSmartPointer<type>::New()
>>>
>>> int main(int argc, char* argv[])
>>> {
>>>        VTK_CREATE(vtkDataSetReader, reader);
>>>        reader->SetFileName("SampleStructGrid.vtk");
>>>        reader->Update();
>>>
>>>        VTK_CREATE(vtkPlane, plane);
>>>        plane->SetOrigin(0.5, 0.5, 0.26);
>>>        plane->SetNormal(0, 0, 1);
>>>
>>>        VTK_CREATE(vtkCutter, cutter);
>>>        cutter->SetCutFunction(plane);
>>>        cutter->SetInputConnection(reader->GetOutputPort());
>>>
>>>        VTK_CREATE(vtkLookupTable, lut);
>>>        lut->SetNumberOfTableValues(10);
>>>        lut->SetHueRange(0.66667, 0);
>>>        lut->Build();
>>>
>>>        VTK_CREATE(vtkDataSetMapper, mapper);
>>>        mapper->SetInputConnection(cutter->GetOutputPort());
>>>        mapper->SetLookupTable(lut);
>>>        mapper->InterpolateScalarsBeforeMappingOn();
>>>        mapper->SetScalarRange(0.3, 1.1);
>>>
>>>        VTK_CREATE(vtkActor, actor);
>>>        actor->SetMapper(mapper);
>>>
>>>        VTK_CREATE(vtkScalarBarActor, bar);
>>>        bar->SetLookupTable(lut);
>>>        bar->GetPositionCoordinate()->SetCoordinateSystemToNormalizedViewport();
>>>        bar->GetPositionCoordinate()->SetValue(0.25, 0.01);
>>>        bar->SetOrientationToHorizontal();
>>>        bar->SetWidth(0.5);
>>>        bar->SetHeight(0.11);
>>>
>>>        VTK_CREATE(vtkRenderer, renderer);
>>>        renderer->AddViewProp(actor);
>>>        renderer->AddViewProp(bar);
>>>        renderer->SetBackground(1, 1, 1);
>>>        renderer->ResetCamera();
>>>
>>>        VTK_CREATE(vtkRenderWindow, window);
>>>        window->OffScreenRenderingOn();
>>>        window->AddRenderer(renderer);
>>>        window->SetSize(600, 600);
>>>
>>>        VTK_CREATE(vtkWindowToImageFilter, wti);
>>>        wti->SetInput(window);
>>>
>>>        VTK_CREATE(vtkPNGWriter, writer);
>>>        writer->SetInputConnection(wti->GetOutputPort());
>>>        writer->SetFileName("test-color.png");
>>>        writer->Write();
>>>
>>>        return 0;
>>> }
>>>
>>> --- End test code ---
>>>