[vtkusers] Setting vtkCamera to custom modelview & volume rendering
Bud Bundy
budric at gmail.com
Fri Aug 5 15:10:16 EDT 2016
Thanks,
The light positions were indeed different, but making them the same
didn't fix it for me. Perhaps my fix is wrong?
void assertArrayEquals(const double * a, const double * b, size_t elements)
{
for (size_t i = 0; i < elements; ++i)
{
assert(a[i] - b[i] <= std::numeric_limits<double>::epsilon());
}
}
//previous int main() code ...
//setting lights before first call to Render() crashes program,
also describedh http://www.vtk.org/Wiki/VTK/Examples/Cxx/Lighting/Light
renderWindow->Render();
renderer2->RemoveAllLights();
vtkSmartPointer<vtkLight> newLight = vtkSmartPointer<vtkLight>::New();
newLight->SetPosition(0, 0, 1000);
renderer2->AddLight(newLight);
//assert lighting is the same
vtkSmartPointer<vtkLightCollection> lightCollection1 =
renderer1->GetLights();
vtkSmartPointer<vtkLightCollection> lightCollection2 =
renderer2->GetLights();
assert(lightCollection1->GetNumberOfItems() ==
lightCollection2->GetNumberOfItems());
lightCollection1->InitTraversal();
lightCollection2->InitTraversal();
vtkSmartPointer<vtkLight> light1 = lightCollection1->GetNextItem();
vtkSmartPointer<vtkLight> light2 = lightCollection2->GetNextItem();
assertArrayEquals(light1->GetPosition(), light2->GetPosition(), 3);
assertArrayEquals(light1->GetTransformedPosition(),
light2->GetTransformedPosition(), 3);
assertArrayEquals(light1->GetFocalPoint(), light2->GetFocalPoint(), 3);
assertArrayEquals(light1->GetTransformedFocalPoint(),
light1->GetTransformedFocalPoint(), 3);
assertArrayEquals(light1->GetAmbientColor(),
light2->GetAmbientColor(), 3);
assertArrayEquals(light1->GetSpecularColor(),
light2->GetSpecularColor(), 3);
assertArrayEquals(light1->GetDiffuseColor(),
light2->GetDiffuseColor(), 3);
renderWindow->Render();
renderWindowInteractor->Start();
On 08/05/16 14:10, David E DeMarle wrote:
>
> 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
> <mailto: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/Examples/Cxx/VolumeRendering/SmartVolumeMapper
> <http://www.vtk.org/Wiki/VTK/Examples/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()->GetPointData()->GetScalars("values");
> double range[2];
> a->GetRange(range);
>
> vtkSmartPointer<vtkImageShiftScale> t =
> vtkSmartPointer<vtkImageShiftScale>::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>::New();
> 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>::New();
> 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.
>
>
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