<div dir="ltr">Please make sure that your sampling distance is less than < 2. You can set the sampling distance manually in the API. </div><br><div class="gmail_quote"><div dir="ltr">On Wed, Oct 4, 2017 at 8:23 AM Elvis Stansvik <<a href="mailto:elvis.stansvik@orexplore.com">elvis.stansvik@orexplore.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi all,<br>
<br>
In the test case below, I render one 200x200x2 volume and one<br>
200x200x3 volume, both with the same settings.<br>
<br>
The 200x200x3 volume looks as expected (the light gray one in the<br>
attached screenshot), while the 200x200x2 one looks strange (too dark,<br>
and with some kind of gradient artifact).<br>
<br>
Is there some limitation on rendering a volume that is only 2 thick in<br>
one of the dimensions? I can understand why a volume of thickness 1<br>
can't be rendered properly, since VTK must have values to interpolate<br>
between, but 2 should be OK right?<br>
<br>
Thanks for any help.<br>
<br>
Elvis<br>
<br>
<br>
main.cpp:<br>
<br>
#include <algorithm><br>
<br>
#include <vtkColorTransferFunction.h><br>
#include <vtkGenericOpenGLRenderWindow.h><br>
#include <vtkGPUVolumeRayCastMapper.h><br>
#include <vtkImageData.h><br>
#include <vtkNew.h><br>
#include <vtkPiecewiseFunction.h><br>
#include <vtkProperty.h><br>
#include <vtkRenderer.h><br>
#include <vtkRenderWindow.h><br>
#include <vtkRenderWindowInteractor.h><br>
#include <vtkVolume.h><br>
#include <vtkVolumeProperty.h><br>
<br>
int main(int argc, char *argv[])<br>
{<br>
    vtkNew<vtkColorTransferFunction> colorFunction;<br>
    colorFunction->AddRGBPoint(0.0, 0.0, 0.0, 0.0);<br>
    colorFunction->AddRGBPoint(1.0, 0.0, 0.0, 0.0);<br>
<br>
    vtkNew<vtkPiecewiseFunction> opacityFunction;<br>
    opacityFunction->AddPoint(0.0, 0.0);<br>
    opacityFunction->AddPoint(1.0, 1.0);<br>
<br>
    // A 200x200x2 volume<br>
    vtkNew<vtkImageData> imageData;<br>
    imageData->SetExtent(0, 199, 0, 199, 0, 1);<br>
    imageData->AllocateScalars(VTK_FLOAT, 1);<br>
    std::fill_n(static_cast<float *>(imageData->GetScalarPointer()),<br>
200 * 200 * 2, 0.01);<br>
<br>
    vtkNew<vtkGPUVolumeRayCastMapper> volumeMapper;<br>
    volumeMapper->SetInputData(imageData.Get());<br>
<br>
    vtkNew<vtkVolumeProperty> volumeProperty;<br>
    volumeProperty->SetScalarOpacity(opacityFunction.Get());<br>
    volumeProperty->SetColor(colorFunction.Get());<br>
    volumeProperty->ShadeOff();<br>
<br>
    vtkNew<vtkVolume> volume;<br>
    volume->SetMapper(volumeMapper.Get());<br>
    volume->SetProperty(volumeProperty.Get());<br>
    volume->SetPosition(120, 0, 0);<br>
<br>
    // A 200x200x3 volume<br>
    vtkNew<vtkImageData> imageData2;<br>
    imageData2->SetExtent(0, 199, 0, 199, 0, 2);<br>
    imageData2->AllocateScalars(VTK_FLOAT, 1);<br>
    std::fill_n(static_cast<float *>(imageData2->GetScalarPointer()),<br>
200 * 200 * 3, 0.01);<br>
<br>
    vtkNew<vtkGPUVolumeRayCastMapper> volumeMapper2;<br>
    volumeMapper2->SetInputData(imageData2.Get());<br>
<br>
    vtkNew<vtkVolumeProperty> volumeProperty2;<br>
    volumeProperty2->SetScalarOpacity(opacityFunction.Get());<br>
    volumeProperty2->SetColor(colorFunction.Get());<br>
    volumeProperty2->ShadeOff();<br>
<br>
    vtkNew<vtkVolume> volume2;<br>
    volume2->SetMapper(volumeMapper2.Get());<br>
    volume2->SetProperty(volumeProperty2.Get());<br>
    volume2->SetPosition(-120, 0, 0);<br>
<br>
    vtkNew<vtkRenderer> renderer;<br>
    renderer->AddVolume(volume.Get());<br>
    renderer->AddVolume(volume2.Get());<br>
    renderer->SetBackground(1.0, 1.0, 1.0);<br>
<br>
    // Render with "plain" render window / interactor<br>
    vtkNew<vtkRenderWindow> window;<br>
    window->SetMultiSamples(0);<br>
    window->AddRenderer(renderer.Get());<br>
<br>
    vtkNew<vtkRenderWindowInteractor> interactor;<br>
    interactor->SetRenderWindow(window.Get());<br>
    interactor->Start();<br>
<br>
    return 0;<br>
}<br>
<br>
<br>
CMakeLists.txt:<br>
<br>
cmake_minimum_required(VERSION 3.1)<br>
<br>
project(TestCase)<br>
<br>
find_package(VTK 8.0 COMPONENTS<br>
    vtkCommonCore<br>
    vtkCommonDataModel<br>
    vtkCommonExecutionModel<br>
    vtkCommonMath<br>
    vtkFiltersSources<br>
    vtkGUISupportQt<br>
    vtkInteractionStyle<br>
    vtkRenderingCore<br>
    vtkRenderingOpenGL2<br>
    vtkRenderingVolume<br>
    vtkRenderingVolumeOpenGL2<br>
    REQUIRED<br>
)<br>
<br>
add_executable(TestCase main.cpp)<br>
<br>
target_link_libraries(TestCase PUBLIC<br>
    vtkCommonCore<br>
    vtkCommonDataModel<br>
    vtkCommonExecutionModel<br>
    vtkCommonMath<br>
    vtkFiltersSources<br>
    vtkInteractionStyle<br>
    vtkRenderingCore<br>
    vtkRenderingOpenGL2<br>
    vtkRenderingVolume<br>
    vtkRenderingVolumeOpenGL2<br>
)<br>
<br>
target_include_directories(TestCase PUBLIC<br>
    ${VTK_INCLUDE_DIRS}<br>
)<br>
<br>
target_compile_definitions(TestCase PUBLIC<br>
    ${VTK_DEFINITIONS}<br>
)<br>
<br>
set_target_properties(TestCase PROPERTIES<br>
    CXX_STANDARD 14<br>
    CXX_STANDARD_REQUIRED ON<br>
)<br>
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</blockquote></div>