<p dir="ltr">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. </p>
<div class="gmail_extra"><br><div class="gmail_quote">On Aug 5, 2016 1:12 PM, "Bud Bundy" <<a href="mailto:budric@gmail.com">budric@gmail.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi,<br>
<br>
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.<br>
<br>
The code is loosely based on: <a href="http://www.vtk.org/Wiki/VTK/Examples/Cxx/VolumeRendering/SmartVolumeMapper" rel="noreferrer" target="_blank">http://www.vtk.org/Wiki/VTK/Ex<wbr>amples/Cxx/VolumeRendering/Sma<wbr>rtVolumeMapper</a><br>
<br>
I'm using VTK 7.0<br>
<br>
#include <vtkActor.h><br>
#include <vtkSmartPointer.h><br>
#include <vtkCubeSource.h><br>
#include <vtkPolyDataMapper.h><br>
#include <vtkRenderWindow.h><br>
#include <vtkRenderer.h><br>
#include <vtkRenderWindowInteractor.h><br>
#include <vtkCamera.h><br>
#include <vtkSphere.h><br>
#include <vtkSampleFunction.h><br>
#include <vtkImageShiftScale.h><br>
#include <vtkImageData.h><br>
#include <vtkPointData.h><br>
#include <vtkSmartVolumeMapper.h><br>
#include <vtkPiecewiseFunction.h><br>
#include <vtkVolumeProperty.h><br>
#include <vtkColorTransferFunction.h><br>
#include <vtkCommand.h><br>
#include <vtkMatrix4x4.h><br>
<br>
vtkSmartPointer<vtkVolume> generateVolume()<br>
{<br>
// Create a spherical implicit function.<br>
vtkSmartPointer<vtkSphere> sphere = vtkSmartPointer<vtkSphere>::Ne<wbr>w();<br>
sphere->SetRadius(0.1);<br>
sphere->SetCenter(0.0, 0.0, 0.0);<br>
<br>
vtkSmartPointer<vtkSampleFunct<wbr>ion> sampleFunction = vtkSmartPointer<vtkSampleFunct<wbr>ion>::New();<br>
sampleFunction->SetImplicitFun<wbr>ction(sphere);<br>
sampleFunction->SetOutputScala<wbr>rTypeToFloat();<br>
sampleFunction->SetSampleDimen<wbr>sions(64, 64, 20);<br>
sampleFunction->SetModelBounds<wbr>(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);<br>
sampleFunction->SetCapping(fal<wbr>se);<br>
sampleFunction->SetComputeNorm<wbr>als(false);<br>
sampleFunction->SetScalarArray<wbr>Name("values");<br>
sampleFunction->Update();<br>
<br>
vtkDataArray* a = sampleFunction->GetOutput()->G<wbr>etPointData()->GetScalars("val<wbr>ues");<br>
double range[2];<br>
a->GetRange(range);<br>
<br>
vtkSmartPointer<vtkImageShiftS<wbr>cale> t = vtkSmartPointer<vtkImageShiftS<wbr>cale>::New();<br>
t->SetInputConnection(sampleFu<wbr>nction->GetOutputPort());<br>
<br>
t->SetShift(-range[0]);<br>
double magnitude = range[1] - range[0];<br>
if (magnitude == 0.0)<br>
{<br>
magnitude = 1.0;<br>
}<br>
t->SetScale(255.0 / magnitude);<br>
t->SetOutputScalarTypeToUnsign<wbr>edChar();<br>
t->Update();<br>
<br>
vtkSmartPointer<vtkImageData> imageData = vtkSmartPointer<vtkImageData>:<wbr>:New();<br>
imageData->ShallowCopy(t->GetO<wbr>utput());<br>
<br>
vtkSmartPointer<vtkSmartVolume<wbr>Mapper> volumeMapper = vtkSmartPointer<vtkSmartVolume<wbr>Mapper>::New();<br>
volumeMapper->SetBlendModeToCo<wbr>mposite(); // composite first<br>
volumeMapper->SetInputData(ima<wbr>geData);<br>
<br>
vtkSmartPointer<vtkVolumePrope<wbr>rty> volumeProperty = vtkSmartPointer<vtkVolumePrope<wbr>rty>::New();<br>
volumeProperty->ShadeOff();<br>
volumeProperty->SetInterpolati<wbr>onType(VTK_LINEAR_<wbr>INTERPOLATION);<br>
<br>
vtkSmartPointer<vtkPiecewiseFu<wbr>nction> compositeOpacity = vtkSmartPointer<vtkPiecewiseFu<wbr>nction>::New();<br>
compositeOpacity->AddPoint(0.0<wbr>, 0.0);<br>
compositeOpacity->AddPoint(80.<wbr>0, 1.0);<br>
compositeOpacity->AddPoint(80.<wbr>1, 0.0);<br>
compositeOpacity->AddPoint(255<wbr>.0, 0.0);<br>
volumeProperty->SetScalarOpaci<wbr>ty(compositeOpacity); // composite first.<br>
<br>
vtkSmartPointer<vtkColorTransf<wbr>erFunction> color = vtkSmartPointer<vtkColorTransf<wbr>erFunction>::New();<br>
color->AddRGBPoint(0.0, 0.0, 0.0, 1.0);<br>
color->AddRGBPoint(40.0, 1.0, 0.0, 0.0);<br>
color->AddRGBPoint(255.0, 1.0, 1.0, 1.0);<br>
volumeProperty->SetColor(color<wbr>);<br>
<br>
vtkSmartPointer<vtkVolume> volume = vtkSmartPointer<vtkVolume>::Ne<wbr>w();<br>
volume->SetMapper(volumeMapper<wbr>);<br>
volume->SetProperty(volumeProp<wbr>erty);<br>
<br>
vtkSmartPointer<vtkMatrix4x4> volumeScaleTransform = vtkSmartPointer<vtkMatrix4x4>:<wbr>:New();<br>
volumeScaleTransform->Identity<wbr>();<br>
volumeScaleTransform->SetEleme<wbr>nt(0, 0, 512);<br>
volumeScaleTransform->SetEleme<wbr>nt(1, 1, 512);<br>
volumeScaleTransform->SetEleme<wbr>nt(2, 2, 160);<br>
volume->SetUserMatrix(volumeSc<wbr>aleTransform);<br>
return volume;<br>
}<br>
<br>
int main()<br>
{<br>
// camera1<br>
vtkSmartPointer<vtkCamera> camera1 = vtkSmartPointer<vtkCamera>::Ne<wbr>w();<br>
camera1->SetPosition(0, 0, 1000);<br>
camera1->SetFocalPoint(0, 0, 0);<br>
camera1->SetClippingRange(0.1, 5000);<br>
camera1->SetViewAngle(60);<br>
<br>
//camera 2<br>
vtkSmartPointer<vtkCamera> camera2 = vtkSmartPointer<vtkCamera>::Ne<wbr>w();<br>
camera2->SetPosition(0, 0, 0); //I do not want any additional translation that comes with default (0,0,1) setting.<br>
camera2->SetFocalPoint(0, 0, -1); //setting this to (0,0,0) causes whole modelview matrix to be 0, regardless of what SetModelTransformMatrix() sets<br>
camera2->SetViewAngle(60);<br>
camera2->SetClippingRange(0.1, 5000);<br>
double modelViewTransform[16] = { 1, 0, 0, 0,<br>
0, 1, 0, 0,<br>
0, 0, 1, -1000,<br>
0, 0, 0, 1 };<br>
camera2->SetModelTransformMatr<wbr>ix(modelViewTransform);<br>
<br>
// renderer1 using camera1<br>
vtkSmartPointer<vtkRenderer> renderer1 = vtkSmartPointer<vtkRenderer>::<wbr>New();<br>
renderer1->SetViewport(0, 0, 0.5, 1);<br>
renderer1->AddVolume(generateV<wbr>olume());<br>
renderer1->SetActiveCamera(cam<wbr>era1);<br>
<br>
// renderer2 using camera2<br>
vtkSmartPointer<vtkRenderer> renderer2 = vtkSmartPointer<vtkRenderer>::<wbr>New();<br>
renderer2->SetViewport(0.5, 0, 1, 1);<br>
renderer2->AddVolume(generateV<wbr>olume());<br>
renderer2->SetActiveCamera(cam<wbr>era2);<br>
<br>
// assert model view matrices are the same<br>
vtkSmartPointer<vtkMatrix4x4> vtkModelViewMatrix1 = renderer1->GetActiveCamera()-><wbr>GetModelViewTransformMatrix();<br>
vtkSmartPointer<vtkMatrix4x4> vtkModelViewMatrix2 = renderer2->GetActiveCamera()-><wbr>GetModelViewTransformMatrix();<br>
for (int i = 0; i < 4; ++i)<br>
for (int j = 0; j < 4; ++j)<br>
assert(vtkModelViewMatrix1->Ge<wbr>tElement(i, j) == vtkModelViewMatrix2->GetElemen<wbr>t(i, j));<br>
<br>
// window and interactor<br>
vtkSmartPointer<vtkRenderWindo<wbr>w> renderWindow = vtkSmartPointer<vtkRenderWindo<wbr>w>::New();<br>
renderWindow->SetSize(1024, 512);<br>
renderWindow->AddRenderer(rend<wbr>erer1);<br>
renderWindow->AddRenderer(rend<wbr>erer2);<br>
vtkSmartPointer<vtkRenderWindo<wbr>wInteractor> renderWindowInteractor = vtkSmartPointer<vtkRenderWindo<wbr>wInteractor>::New();<br>
renderWindowInteractor->SetRen<wbr>derWindow(renderWindow);<br>
<br>
renderWindow->Render();<br>
renderWindowInteractor->Start(<wbr>);<br>
<br>
return EXIT_SUCCESS;<br>
}<br>
<br>
<br>
Thank you very much.<br>
<br>
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<br></blockquote></div></div>