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

[David Gobbi]

Hmm... yes, if things are like you say, then it is not a bug in OSMesa.
Something must have changed in the Mapper code.  Hopefully someone
on the list knows why InterpolateScalarsBeforeMappingOn() would behave
differently than it used to.

 - David


On Tue, Apr 5, 2011 at 8:11 AM, Riku <subs at collab.se> wrote:
> Hi David,
>
> Thank you for the suggestion. I just tested it, and attached the
> result here. Although it seems that the number of colors are more
> "correct", the image itself is not of much use in that state.
>
> But the main thing is: this behaviour appeared _after_ VTK 5.6.1. I
> have tried the exact same code compiled with (1) VTK 5.6.1 and with
> (2) the VTK release head, both linking to the same libOSMesa library
> (on the same machine). It seems unlikely the OpenGL implementation is
> changing here.
>
> This issue is one of very few remaining in a current task, and I'd
> love to get it resolved.
>
> Thanks for any further help,
>
> Riku
>
>
> On 5 April 2011 15:35, David Gobbi <david.gobbi at gmail.com> wrote:
>> 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 ---
>>>>>
>>
>