[vtkusers] Strange rendering with 2-voxel thick volume

[Elvis Stansvik]

2017-10-04 17:43 GMT+02:00 Aashish Chaudhary <aashish.chaudhary at kitware.com>:
> thanks..I just wanted to make sure that we remove that as one of the
> culprit. I am wondering if it is something to do with the geometry (bbox) or
> something to do with some edge case (calculation that is going off because
> of very small delta). Although in the past we have tried very think volumes
>
> Is it possible for you to send a sample dataset to us?

My test case includes the data used. It's simply a 200x200x2 volume
filled with all data points set to 0.01.

Elvis

>
> On Wed, Oct 4, 2017 at 10:09 AM Elvis Stansvik
> <elvis.stansvik at orexplore.com> wrote:
>>
>> Hi Aashish,
>>
>> 2017-10-04 15:47 GMT+02:00 Aashish Chaudhary
>> <aashish.chaudhary at kitware.com>:
>> > Please make sure that your sampling distance is less than < 2. You can
>> > set
>> > the sampling distance manually in the API.
>>
>> Hm. I don't think it's related to sampling distance. In the test case
>> I'm not setting sampling distance at all, so I think it should default
>> to 1, and then be automatically adjusted during interaction.
>>
>> In any case, even if I amend the test case with e.g.:
>>
>>     volumeMapper->AutoAdjustSampleDistancesOff();
>>     volumeMapper->SetSampleDistance(0.2);
>>     ...
>>     volumeMapper2->AutoAdjustSampleDistancesOff();
>>     volumeMapper2->SetSampleDistance(0.2);
>>
>> The result is the same.
>>
>> Elvis
>>
>> >
>> > On Wed, Oct 4, 2017 at 8:23 AM Elvis Stansvik
>> > <elvis.stansvik at orexplore.com>
>> > wrote:
>> >>
>> >> Hi all,
>> >>
>> >> In the test case below, I render one 200x200x2 volume and one
>> >> 200x200x3 volume, both with the same settings.
>> >>
>> >> The 200x200x3 volume looks as expected (the light gray one in the
>> >> attached screenshot), while the 200x200x2 one looks strange (too dark,
>> >> and with some kind of gradient artifact).
>> >>
>> >> Is there some limitation on rendering a volume that is only 2 thick in
>> >> one of the dimensions? I can understand why a volume of thickness 1
>> >> can't be rendered properly, since VTK must have values to interpolate
>> >> between, but 2 should be OK right?
>> >>
>> >> Thanks for any help.
>> >>
>> >> Elvis
>> >>
>> >>
>> >> main.cpp:
>> >>
>> >> #include <algorithm>
>> >>
>> >> #include <vtkColorTransferFunction.h>
>> >> #include <vtkGenericOpenGLRenderWindow.h>
>> >> #include <vtkGPUVolumeRayCastMapper.h>
>> >> #include <vtkImageData.h>
>> >> #include <vtkNew.h>
>> >> #include <vtkPiecewiseFunction.h>
>> >> #include <vtkProperty.h>
>> >> #include <vtkRenderer.h>
>> >> #include <vtkRenderWindow.h>
>> >> #include <vtkRenderWindowInteractor.h>
>> >> #include <vtkVolume.h>
>> >> #include <vtkVolumeProperty.h>
>> >>
>> >> int main(int argc, char *argv[])
>> >> {
>> >>     vtkNew<vtkColorTransferFunction> colorFunction;
>> >>     colorFunction->AddRGBPoint(0.0, 0.0, 0.0, 0.0);
>> >>     colorFunction->AddRGBPoint(1.0, 0.0, 0.0, 0.0);
>> >>
>> >>     vtkNew<vtkPiecewiseFunction> opacityFunction;
>> >>     opacityFunction->AddPoint(0.0, 0.0);
>> >>     opacityFunction->AddPoint(1.0, 1.0);
>> >>
>> >>     // A 200x200x2 volume
>> >>     vtkNew<vtkImageData> imageData;
>> >>     imageData->SetExtent(0, 199, 0, 199, 0, 1);
>> >>     imageData->AllocateScalars(VTK_FLOAT, 1);
>> >>     std::fill_n(static_cast<float *>(imageData->GetScalarPointer()),
>> >> 200 * 200 * 2, 0.01);
>> >>
>> >>     vtkNew<vtkGPUVolumeRayCastMapper> volumeMapper;
>> >>     volumeMapper->SetInputData(imageData.Get());
>> >>
>> >>     vtkNew<vtkVolumeProperty> volumeProperty;
>> >>     volumeProperty->SetScalarOpacity(opacityFunction.Get());
>> >>     volumeProperty->SetColor(colorFunction.Get());
>> >>     volumeProperty->ShadeOff();
>> >>
>> >>     vtkNew<vtkVolume> volume;
>> >>     volume->SetMapper(volumeMapper.Get());
>> >>     volume->SetProperty(volumeProperty.Get());
>> >>     volume->SetPosition(120, 0, 0);
>> >>
>> >>     // A 200x200x3 volume
>> >>     vtkNew<vtkImageData> imageData2;
>> >>     imageData2->SetExtent(0, 199, 0, 199, 0, 2);
>> >>     imageData2->AllocateScalars(VTK_FLOAT, 1);
>> >>     std::fill_n(static_cast<float *>(imageData2->GetScalarPointer()),
>> >> 200 * 200 * 3, 0.01);
>> >>
>> >>     vtkNew<vtkGPUVolumeRayCastMapper> volumeMapper2;
>> >>     volumeMapper2->SetInputData(imageData2.Get());
>> >>
>> >>     vtkNew<vtkVolumeProperty> volumeProperty2;
>> >>     volumeProperty2->SetScalarOpacity(opacityFunction.Get());
>> >>     volumeProperty2->SetColor(colorFunction.Get());
>> >>     volumeProperty2->ShadeOff();
>> >>
>> >>     vtkNew<vtkVolume> volume2;
>> >>     volume2->SetMapper(volumeMapper2.Get());
>> >>     volume2->SetProperty(volumeProperty2.Get());
>> >>     volume2->SetPosition(-120, 0, 0);
>> >>
>> >>     vtkNew<vtkRenderer> renderer;
>> >>     renderer->AddVolume(volume.Get());
>> >>     renderer->AddVolume(volume2.Get());
>> >>     renderer->SetBackground(1.0, 1.0, 1.0);
>> >>
>> >>     // Render with "plain" render window / interactor
>> >>     vtkNew<vtkRenderWindow> window;
>> >>     window->SetMultiSamples(0);
>> >>     window->AddRenderer(renderer.Get());
>> >>
>> >>     vtkNew<vtkRenderWindowInteractor> interactor;
>> >>     interactor->SetRenderWindow(window.Get());
>> >>     interactor->Start();
>> >>
>> >>     return 0;
>> >> }
>> >>
>> >>
>> >> CMakeLists.txt:
>> >>
>> >> cmake_minimum_required(VERSION 3.1)
>> >>
>> >> project(TestCase)
>> >>
>> >> find_package(VTK 8.0 COMPONENTS
>> >>     vtkCommonCore
>> >>     vtkCommonDataModel
>> >>     vtkCommonExecutionModel
>> >>     vtkCommonMath
>> >>     vtkFiltersSources
>> >>     vtkGUISupportQt
>> >>     vtkInteractionStyle
>> >>     vtkRenderingCore
>> >>     vtkRenderingOpenGL2
>> >>     vtkRenderingVolume
>> >>     vtkRenderingVolumeOpenGL2
>> >>     REQUIRED
>> >> )
>> >>
>> >> add_executable(TestCase main.cpp)
>> >>
>> >> target_link_libraries(TestCase PUBLIC
>> >>     vtkCommonCore
>> >>     vtkCommonDataModel
>> >>     vtkCommonExecutionModel
>> >>     vtkCommonMath
>> >>     vtkFiltersSources
>> >>     vtkInteractionStyle
>> >>     vtkRenderingCore
>> >>     vtkRenderingOpenGL2
>> >>     vtkRenderingVolume
>> >>     vtkRenderingVolumeOpenGL2
>> >> )
>> >>
>> >> target_include_directories(TestCase PUBLIC
>> >>     ${VTK_INCLUDE_DIRS}
>> >> )
>> >>
>> >> target_compile_definitions(TestCase PUBLIC
>> >>     ${VTK_DEFINITIONS}
>> >> )
>> >>
>> >> set_target_properties(TestCase PROPERTIES
>> >>     CXX_STANDARD 14
>> >>     CXX_STANDARD_REQUIRED ON
>> >> )
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