[vtk-developers] UseJitteringOn() has no effect in 7.1.0.rc1

Sat Oct 15 06:19:48 EDT 2016

2016-10-15 12:10 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
> 2016-10-15 11:19 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>> 2016-10-15 11:16 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
>>> 2016-10-14 15:54 GMT+02:00 Alvaro Sanchez <alvaro.sanchez at kitware.com>:
>>>> Hi Elvis,
>>>>
>>>> the mapper uses a vtkPerlinNoise instance to generate the jitter noise and
>>>> as far as I know there are currently no knobs exposed to tweak the amount of
>>>> ray perturbation.  Are you using the GL2 backend?  It would also be good to
>>>> know what features are active along with ray jittering (multiple components,
>>>> etc.), so if you could provide some sample data or code would be very
>>>> helpful.
>>>
>>> Hi again Alvaro,
>>>
>>> Here's a minimal test case including sample data (129 MB):
>>>
>>>     https://dl.dropboxusercontent.com/u/22350696/test_grain.tar.gz
>>
>> In case I ever take that down from Dropbox, this was the code:
>>
>> #include <vtkCamera.h>
>> #include <vtkColorTransferFunction.h>
>> #include <vtkGPUVolumeRayCastMapper.h>
>> #include <vtkImageData.h>
>> #include <vtkPiecewiseFunction.h>
>> #include <vtkRenderer.h>
>> #include <vtkRenderWindow.h>
>> #include <vtkRenderWindowInteractor.h>
>> #include <vtkSmartPointer.h>
>> #include <vtkVolume.h>
>> #include <vtkVolumeProperty.h>
>> #include <vtkXMLImageDataReader.h>
>>
>> #include <iostream>
>>
>> int main(int argc, char *argv[])
>> {
>>     if (argc != 2) {
>>         std::cerr << "Usage: test_grain <xmlfile>" << std::endl;
>>         return 1;
>>     }
>>
>>     auto reader = vtkSmartPointer<vtkXMLImageDataReader>::New();
>>     reader->SetFileName(argv[1]);
>>     reader->Update();
>>
>>     auto imageData = reader->GetOutput();
>>
>>     auto mapper = vtkSmartPointer<vtkGPUVolumeRayCastMapper>::New();
>>     mapper->SetInputConnection(reader->GetOutputPort());
>>     mapper->UseJitteringOn();
>>
>>     auto property = vtkSmartPointer<vtkVolumeProperty>::New();
>>     property->SetInterpolationTypeToLinear();
>>     property->SetScalarOpacityUnitDistance(imageData->GetSpacing()[0]);
>
> And in case you wonder about this call to
> SetScalarOpacityUnitDistance, it's because in our program we work with
> two versions of the same volume data, one "low res" version (larger
> spacing) which is what you see in the left view in my earlier
> screenshots, and one "high res" version (smaller spacing) which is
> what you see in the central view. Both versions use the same opacity
> function, and to get the same look in both versions, we set the
> ScalarOpacityUnitDistance to the spacing of the volume. See my recent
> thread for more info [1], and especially Sankesh's second answer.
>
> This got me thinking, could the fact that I have a quite small spacing
> be a cause for the jittering to not have any noticable effect? In the
> sample/test case I linked to, the spacing is 0.0002 (corresponding to
> centimeters). This is just an idea, I don't know if the volume spacing

Sorry, corresponding to meters I mean of course :)

Elvis

> could/does have any effect on the result of enabling jittering.
>
> Elvis
>
> [1] http://public.kitware.com/pipermail/vtkusers/2016-September/096543.html
>
>>     property->ShadeOff();
>>
>>     auto opacity = vtkSmartPointer<vtkPiecewiseFunction>::New();
>>     opacity->AddPoint(0.000, 0.00);
>>     opacity->AddPoint(0.800, 0.00);
>>     opacity->AddPoint(2.000, 0.70);
>>     opacity->AddPoint(3.500, 1.00);
>>     opacity->AddPoint(20.000, 1.00);
>>     property->SetScalarOpacity(opacity);
>>
>>     auto color = vtkSmartPointer<vtkColorTransferFunction>::New();
>>     color->AddRGBPoint(0.000, 0.70, 0.70, 0.50);
>>     color->AddRGBPoint(3.500, 0.00, 0.00, 0.00);
>>     color->AddRGBPoint(20.000, 0.00, 0.00, 0.00);
>>     property->SetColor(color);
>>
>>     auto volume = vtkSmartPointer<vtkVolume>::New();
>>     volume->SetMapper(mapper);
>>     volume->SetProperty(property);
>>
>>     auto renderer = vtkSmartPointer<vtkRenderer>::New();
>>     renderer->SetBackground(1.0, 1.0, 1.0);
>>     renderer->AddVolume(volume);
>>
>>     auto window = vtkSmartPointer<vtkRenderWindow>::New();
>>     window->AddRenderer(renderer);
>>     window->SetSize(600, 600);
>>
>>     auto interactor = vtkSmartPointer<vtkRenderWindowInteractor>::New();
>>     interactor->SetRenderWindow(window);
>>
>>     auto camera = renderer->GetActiveCamera();
>>     camera->SetParallelProjection(true);
>>     camera->SetPosition(1.0, 0.0, 0.0);
>>     camera->SetViewUp(0, 0, 1);
>>
>>     renderer->ResetCamera();
>>
>>     window->Render();
>>     interactor->Start();
>>
>>     return 0;
>> }
>>
>> Elvis
>>
>>>
>>> Build with:
>>>
>>>     cmake .
>>>     make
>>>
>>> and run with:
>>>
>>>     ./test_grain rec-0300mm-0400mm.xml
>>>
>>> The result should be as in the attached screenshot.
>>>
>>> Elvis
>>>
>>>>
>>>> Thanks!
>>>> Alvaro
>>>>
>>>> On Fri, Oct 14, 2016 at 3:47 AM, Elvis Stansvik
>>>> <elvis.stansvik at orexplore.com> wrote:
>>>>>
>>>>> Hi all,
>>>>>
>>>>> I updated our product to use VTK 7.1.0.rc1, as I was interested in
>>>>> trying out vtkGPUVolumeRayCastMapper::UseJitteringOn() to get rid of
>>>>> some woodgrain effects we're suffering from in our volume rendering
>>>>> (mostly when the volumes are rendered very opaque).
>>>>>
>>>>> But turning the option on seems to have little to no effect. This is
>>>>> the result with the option on:
>>>>>
>>>>>     https://dl.dropboxusercontent.com/u/22350696/out.ogv
>>>>>
>>>>> It looks about the same to me as it does with the option off.
>>>>>
>>>>> Are there any knobs for this option? How does it determine how much to
>>>>> perturbate the rays?
>>>>>
>>>>> Thanks for any advise.
>>>>>
>>>>> Elvis
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>>>>
>>>>
>>>>
>>>> --
>>>> Alvaro Sanchez
>>>> Kitware, Inc.
>>>> Senior R&D Engineer
>>>> 21 Corporate Drive
>>>> Clifton Park, NY 12065-8662
>>>> Phone: 518-881-4901