[vtkusers] Setting vtkCamera to custom modelview & volume rendering

[David E DeMarle]

I was just doing a very similar thing and noticed that light positions are
only updated with the set origin, focal point and up. I ended up computing
those for my intended matrix and lighting then worked as expected.

On Aug 5, 2016 1:12 PM, "Bud Bundy" <budric at gmail.com> wrote:

> Hi,
>
> I need to setup the camera to an arbitrary modelview matrix I have in
> memory.  I managed to get some code working such that
> GetModelViewTransformMatrix() returns the modelview I have/want. However
> the volume rendering is sometimes blank, and I don't understand why because
> the volume is in front of the camera.  I managed to boil down the problem
> to the following code below. camera1 and camera2 have the same modelview
> transform, however the rendering look very different (I've attached a
> screen shot) - though not blank it's a lot dimmer.
>
> The code is loosely based on: http://www.vtk.org/Wiki/VTK/Ex
> amples/Cxx/VolumeRendering/SmartVolumeMapper
>
> I'm using VTK 7.0
>
> #include <vtkActor.h>
> #include <vtkSmartPointer.h>
> #include <vtkCubeSource.h>
> #include <vtkPolyDataMapper.h>
> #include <vtkRenderWindow.h>
> #include <vtkRenderer.h>
> #include <vtkRenderWindowInteractor.h>
> #include <vtkCamera.h>
> #include <vtkSphere.h>
> #include <vtkSampleFunction.h>
> #include <vtkImageShiftScale.h>
> #include <vtkImageData.h>
> #include <vtkPointData.h>
> #include <vtkSmartVolumeMapper.h>
> #include <vtkPiecewiseFunction.h>
> #include <vtkVolumeProperty.h>
> #include <vtkColorTransferFunction.h>
> #include <vtkCommand.h>
> #include <vtkMatrix4x4.h>
>
> vtkSmartPointer<vtkVolume> generateVolume()
> {
>     // Create a spherical implicit function.
>     vtkSmartPointer<vtkSphere> sphere = vtkSmartPointer<vtkSphere>::New();
>     sphere->SetRadius(0.1);
>     sphere->SetCenter(0.0, 0.0, 0.0);
>
>     vtkSmartPointer<vtkSampleFunction> sampleFunction =
> vtkSmartPointer<vtkSampleFunction>::New();
>     sampleFunction->SetImplicitFunction(sphere);
>     sampleFunction->SetOutputScalarTypeToFloat();
>     sampleFunction->SetSampleDimensions(64, 64, 20);
>     sampleFunction->SetModelBounds(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
>     sampleFunction->SetCapping(false);
>     sampleFunction->SetComputeNormals(false);
>     sampleFunction->SetScalarArrayName("values");
>     sampleFunction->Update();
>
>     vtkDataArray* a = sampleFunction->GetOutput()->G
> etPointData()->GetScalars("values");
>     double range[2];
>     a->GetRange(range);
>
>     vtkSmartPointer<vtkImageShiftScale> t = vtkSmartPointer<vtkImageShiftS
> cale>::New();
>     t->SetInputConnection(sampleFunction->GetOutputPort());
>
>     t->SetShift(-range[0]);
>     double magnitude = range[1] - range[0];
>     if (magnitude == 0.0)
>     {
>         magnitude = 1.0;
>     }
>     t->SetScale(255.0 / magnitude);
>     t->SetOutputScalarTypeToUnsignedChar();
>     t->Update();
>
>     vtkSmartPointer<vtkImageData> imageData =
> vtkSmartPointer<vtkImageData>::New();
>     imageData->ShallowCopy(t->GetOutput());
>
>     vtkSmartPointer<vtkSmartVolumeMapper> volumeMapper =
> vtkSmartPointer<vtkSmartVolumeMapper>::New();
>     volumeMapper->SetBlendModeToComposite(); // composite first
>     volumeMapper->SetInputData(imageData);
>
>     vtkSmartPointer<vtkVolumeProperty> volumeProperty =
> vtkSmartPointer<vtkVolumeProperty>::New();
>     volumeProperty->ShadeOff();
> volumeProperty->SetInterpolationType(VTK_LINEAR_INTERPOLATION);
>
>     vtkSmartPointer<vtkPiecewiseFunction> compositeOpacity =
> vtkSmartPointer<vtkPiecewiseFunction>::New();
>     compositeOpacity->AddPoint(0.0, 0.0);
>     compositeOpacity->AddPoint(80.0, 1.0);
>     compositeOpacity->AddPoint(80.1, 0.0);
>     compositeOpacity->AddPoint(255.0, 0.0);
>     volumeProperty->SetScalarOpacity(compositeOpacity); // composite
> first.
>
>     vtkSmartPointer<vtkColorTransferFunction> color =
> vtkSmartPointer<vtkColorTransferFunction>::New();
>     color->AddRGBPoint(0.0, 0.0, 0.0, 1.0);
>     color->AddRGBPoint(40.0, 1.0, 0.0, 0.0);
>     color->AddRGBPoint(255.0, 1.0, 1.0, 1.0);
>     volumeProperty->SetColor(color);
>
>     vtkSmartPointer<vtkVolume> volume = vtkSmartPointer<vtkVolume>::New();
>     volume->SetMapper(volumeMapper);
>     volume->SetProperty(volumeProperty);
>
>     vtkSmartPointer<vtkMatrix4x4> volumeScaleTransform =
> vtkSmartPointer<vtkMatrix4x4>::New();
>     volumeScaleTransform->Identity();
>     volumeScaleTransform->SetElement(0, 0, 512);
>     volumeScaleTransform->SetElement(1, 1, 512);
>     volumeScaleTransform->SetElement(2, 2, 160);
>     volume->SetUserMatrix(volumeScaleTransform);
>     return volume;
> }
>
> int main()
> {
>     // camera1
>     vtkSmartPointer<vtkCamera> camera1 = vtkSmartPointer<vtkCamera>::Ne
> w();
>     camera1->SetPosition(0, 0, 1000);
>     camera1->SetFocalPoint(0, 0, 0);
>     camera1->SetClippingRange(0.1, 5000);
>     camera1->SetViewAngle(60);
>
>     //camera 2
>     vtkSmartPointer<vtkCamera> camera2 = vtkSmartPointer<vtkCamera>::Ne
> w();
>     camera2->SetPosition(0, 0, 0);            //I do not want any
> additional translation that comes with default (0,0,1) setting.
>     camera2->SetFocalPoint(0, 0, -1);       //setting this to (0,0,0)
> causes whole modelview matrix to be 0, regardless of what
> SetModelTransformMatrix() sets
>     camera2->SetViewAngle(60);
>     camera2->SetClippingRange(0.1, 5000);
>     double modelViewTransform[16] = { 1, 0, 0, 0,
>         0, 1, 0, 0,
>         0, 0, 1, -1000,
>         0, 0, 0, 1 };
>     camera2->SetModelTransformMatrix(modelViewTransform);
>
>     // renderer1 using camera1
>     vtkSmartPointer<vtkRenderer> renderer1 = vtkSmartPointer<vtkRenderer>::
> New();
>     renderer1->SetViewport(0, 0, 0.5, 1);
>     renderer1->AddVolume(generateVolume());
>     renderer1->SetActiveCamera(camera1);
>
>     // renderer2 using camera2
>     vtkSmartPointer<vtkRenderer> renderer2 = vtkSmartPointer<vtkRenderer>::
> New();
>     renderer2->SetViewport(0.5, 0, 1, 1);
>     renderer2->AddVolume(generateVolume());
>     renderer2->SetActiveCamera(camera2);
>
>     // assert model view matrices are the same
>     vtkSmartPointer<vtkMatrix4x4> vtkModelViewMatrix1 =
> renderer1->GetActiveCamera()->GetModelViewTransformMatrix();
>     vtkSmartPointer<vtkMatrix4x4> vtkModelViewMatrix2 =
> renderer2->GetActiveCamera()->GetModelViewTransformMatrix();
>     for (int i = 0; i < 4; ++i)
>         for (int j = 0; j < 4; ++j)
>             assert(vtkModelViewMatrix1->GetElement(i, j) ==
> vtkModelViewMatrix2->GetElement(i, j));
>
>     // window and interactor
>     vtkSmartPointer<vtkRenderWindow> renderWindow =
> vtkSmartPointer<vtkRenderWindow>::New();
>     renderWindow->SetSize(1024, 512);
>     renderWindow->AddRenderer(renderer1);
>     renderWindow->AddRenderer(renderer2);
>     vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
> vtkSmartPointer<vtkRenderWindowInteractor>::New();
>     renderWindowInteractor->SetRenderWindow(renderWindow);
>
>     renderWindow->Render();
>     renderWindowInteractor->Start();
>
>     return EXIT_SUCCESS;
> }
>
>
> Thank you very much.
>
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at http://www.kitware.com/
> opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at:
> http://www.vtk.org/Wiki/VTK_FAQ
>
> Search the list archives at: http://markmail.org/search/?q=vtkusers
>
> Follow this link to subscribe/unsubscribe:
> http://public.kitware.com/mailman/listinfo/vtkusers
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://public.kitware.com/pipermail/vtkusers/attachments/20160805/d174fcec/attachment.html>