[vtkusers] Strange rendering with 2-voxel thick volume
Elvis Stansvik
elvis.stansvik at orexplore.com
Thu Oct 5 04:38:36 EDT 2017
2017-10-04 18:12 GMT+02:00 Aashish Chaudhary <aashish.chaudhary at kitware.com>:
> Got it, thanks!
Although I'm not familiar at all with the code, I suspect this is what
happens with my 200x200x2 volume:
In void vtkOpenGLGPUVolumeRayCastMapper::vtkInternal::ComputeCellToPointMatrix()
{
this->CellToPointMatrix->Identity();
this->AdjustedTexMin[0] = this->AdjustedTexMin[1] =
this->AdjustedTexMin[2] = 0.0f;
this->AdjustedTexMin[3] = 1.0f;
this->AdjustedTexMax[0] = this->AdjustedTexMax[1] =
this->AdjustedTexMax[2] = 1.0f;
this->AdjustedTexMax[3] = 1.0f;
if (!this->Parent->CellFlag) // point data
{
float delta[3];
delta[0] = this->Extents[1] - this->Extents[0];
delta[1] = this->Extents[3] - this->Extents[2];
delta[2] = this->Extents[5] - this->Extents[4];
float min[3];
min[0] = 0.5f / delta[0];
min[1] = 0.5f / delta[1];
min[2] = 0.5f / delta[2];
float range[3]; // max - min
range[0] = (delta[0] - 0.5f) / delta[0] - min[0];
range[1] = (delta[1] - 0.5f) / delta[1] - min[1];
range[2] = (delta[2] - 0.5f) / delta[2] - min[2];
this->CellToPointMatrix->SetElement(0, 0, range[0]); // Scale diag
this->CellToPointMatrix->SetElement(1, 1, range[1]);
this->CellToPointMatrix->SetElement(2, 2, range[2]);
this->CellToPointMatrix->SetElement(0, 3, min[0]); // t vector
this->CellToPointMatrix->SetElement(1, 3, min[1]);
this->CellToPointMatrix->SetElement(2, 3, min[2]);
// Adjust limit coordinates for texture access.
float const zeros[4] = {0.0f, 0.0f, 0.0f, 1.0f}; // GL tex min
float const ones[4] = {1.0f, 1.0f, 1.0f, 1.0f}; // GL tex max
this->CellToPointMatrix->MultiplyPoint(zeros, this->AdjustedTexMin);
this->CellToPointMatrix->MultiplyPoint(ones, this->AdjustedTexMax);
}
}
delta[2] = 1 ==> min[2] = 0.5 ==> range[2] = 0
So the scale factor in the third dimension will be 0 in
CellToPointMatrix, right? I guess this could be what accounts for the
strange rendering?
Could/should this code be updated to take into account when the extent
delta is just 1, so that volumes 2 data points thick can be rendered?
Elvis
>
> On Wed, Oct 4, 2017 at 12:07 PM Elvis Stansvik
> <elvis.stansvik at orexplore.com> wrote:
>>
>> 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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>> >> >>
>> >> >> Please keep messages on-topic and check the VTK FAQ at:
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