[vtkusers] Artifacts along bounding box edges in volume rendering

[Róbert Špir]

I used the default parameters from paraview as described here https://blog.kitware.com/new-fxaa-anti-aliasing-option-in-paraviewvtk/

Robert

-----Original Message-----
From: Elvis Stansvik [mailto:elvis.stansvik at orexplore.com] 
Sent: Monday, March 13, 2017 9:54 AM
To: Róbert Špir <spir.robert at gmail.com>
Cc: VTK Users <vtkusers at vtk.org>
Subject: Re: [vtkusers] Artifacts along bounding box edges in volume rendering

2017-03-13 8:10 GMT+01:00 Róbert Špir <spir.robert at gmail.com>:
> Hi Elvis,
> this is caused by multisampling, if you set 
> window->SetMultiSamples(0); the artifact will disappear. I can 
> reproduce it in your example on windows with nvidia card.
>
> If you need antialiasing, you can try using FXAA which doesn't produce 
> these artifacts #include <vtkFXAAOptions.h>
>
>         vtkSmartPointer<vtkFXAAOptions> FXAAOptions = 
> vtkSmartPointer<vtkFXAAOptions>::New();
>         FXAAOptions->SetRelativeContrastThreshold(0.125);
>         FXAAOptions->SetHardContrastThreshold(0.045);
>         FXAAOptions->SetSubpixelBlendLimit(0.75);
>         FXAAOptions->SetSubpixelContrastThreshold(0.25);
>         FXAAOptions->SetUseHighQualityEndpoints(true);
>         FXAAOptions->SetEndpointSearchIterations(12);
>
>         renderer->SetFXAAOptions(FXAAOptions);
>         renderer->SetUseFXAA(true);
>
> Robert

That indeed did the trick, and I can't see any ill effects of FXAA for my use case. Many thanks!

Just a question: The parameters above, how did you derive them? Manual tuning to your use case, or my test case?

Elvis

>
> -----Original Message-----
> From: vtkusers [mailto:vtkusers-bounces at vtk.org] On Behalf Of Elvis 
> Stansvik
> Sent: Monday, March 13, 2017 7:53 AM
> To: VTK Users <vtkusers at vtk.org>
> Subject: Re: [vtkusers] Artifacts along bounding box edges in volume 
> rendering
>
> 2017-03-10 10:11 GMT+01:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>> 2017-03-10 10:07 GMT+01:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>>> Hi all,
>>>
>>> I'm trying to debug a problem with artifacts appearing around the 
>>> bounding box edges in my volume rendering (at certain camera angles).
>>> I can reproduce the problem with the minimal test case below. In the 
>>> attached screen shot, notice the faint white artifacts along the 
>>> bounding box edges.
>>>
>>> Anyone know where these come from and how I can fix it?
>>
>> I forgot to say, this is with VTK 7.1.0.
>
> Noone who knows where this comes from? Would be great if someone could 
> confirm that they can reproduce it with my test case, as I'm beginning 
> to suspect it might be graphics card specific (I'm on Linux, Intel graphics).
>
> Should I post to vtk-dev perhaps?
>
> Elvis
>
>>
>> Elvis
>>
>>>
>>> Thanks in advance,
>>> Elvis
>>>
>>>
>>> main.cpp:
>>>
>>> #include <algorithm>
>>>
>>> #include <vtkCamera.h>
>>> #include <vtkColorTransferFunction.h> #include 
>>> <vtkGPUVolumeRayCastMapper.h> #include <vtkImageData.h> #include 
>>> <vtkNew.h> #include <vtkPiecewiseFunction.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);
>>>
>>>     vtkNew<vtkImageData> data;
>>>     data->SetExtent(0, 200, 0, 200, 0, 200);
>>>     data->AllocateScalars(VTK_FLOAT, 1);
>>>     std::fill_n(static_cast<float *>(data->GetScalarPointer()), 
>>> 8000000, 0.1);
>>>
>>>     vtkNew<vtkGPUVolumeRayCastMapper> mapper;
>>>     mapper->SetInputData(data.Get());
>>>
>>>     vtkNew<vtkVolumeProperty> property;
>>>     property->SetScalarOpacity(opacityFunction.Get());
>>>     property->SetColor(colorFunction.Get());
>>>
>>>     vtkNew<vtkVolume> volume;
>>>     volume->SetMapper(mapper.Get());
>>>     volume->SetProperty(property.Get());
>>>
>>>     vtkNew<vtkRenderer> renderer;
>>>     renderer->AddVolume(volume.Get());
>>>     renderer->SetBackground(1.0, 1.0, 1.0);
>>>
>>>     vtkNew<vtkRenderWindow> window;
>>>     window->AddRenderer(renderer.Get());
>>>
>>>     // Position camera such that artifacts appear
>>>     auto camera = renderer->GetActiveCamera();
>>>     camera->SetPosition(500.0, 220.0, 500.0);
>>>     camera->SetFocalPoint(0.0, 80.0, 0.0);
>>>     renderer->ResetCameraClippingRange();
>>>
>>>     vtkNew<vtkRenderWindowInteractor> interactor;
>>>     interactor->SetRenderWindow(window.Get());
>>>     interactor->Start();
>>>
>>>     return 0;
>>> }
>>>
>>>
>>> CMakeLists.txt:
>>>
>>> cmake_minimum_required(VERSION 3.1)
>>>
>>> project(TestCase)
>>>
>>> set(CMAKE_PREFIX_PATH ${CMAKE_PREFIX_PATH} /opt/VTK7)
>>>
>>> find_package(VTK 7.1 COMPONENTS
>>>     vtkCommonCore
>>>     vtkCommonDataModel
>>>     vtkCommonExecutionModel
>>>     vtkCommonMath
>>>     vtkInteractionStyle
>>>     vtkRenderingCore
>>>     vtkRenderingOpenGL2
>>>     vtkRenderingVolume
>>>     vtkRenderingVolumeOpenGL2
>>>     REQUIRED
>>> )
>>>
>>> add_executable(TestCase WIN32 main.cpp)
>>>
>>> target_link_libraries(TestCase PUBLIC
>>>     vtkCommonCore
>>>     vtkCommonDataModel
>>>     vtkCommonExecutionModel
>>>     vtkCommonMath
>>>     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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