[vtkusers] Light source similar to a flashlight?

[Bill Lorensen]

The resolution of the plane is too small (it is one polygon). Set its
resolution to 100 and everything works ok.

On Sun, Nov 25, 2012 at 8:37 AM, David Doria <daviddoria at gmail.com> wrote:
> On Sun, Nov 25, 2012 at 8:27 AM, Bill Lorensen <bill.lorensen at gmail.com>
> wrote:
>>
>> Apparently, if the renderer has a light at the first render, it does
>> not create a default light.
>
>
> Strange, that is not the behavior I'd expect.
>
>>
>> Move the AddLight after renderWindow->Render(); and you'll see the
>> original light also.
>
>
> With the following code, the back side of the plane/sphere are now indeed
> again visible. However, the red light (the diffuse color) is applied to the
> sphere (the yellow sphere has some hints of red/orange), but does not seem
> to be applied to the plane? That is, I would expect a red circle to be
> visible on the plane (and then the plane would be it's normal gray outside
> of this circle).
>
> #include <vtkLightCollection.h>
>
> #include <vtkProperty.h>
>
> #include <vtkRenderer.h>
>
> #include <vtkRenderWindow.h>
>
> #include <vtkPlaneSource.h>
>
> #include <vtkSphereSource.h>
>
> #include <vtkPolyDataMapper.h>
>
> #include <vtkActor.h>
>
> #include <vtkLight.h>
>
> #include <vtkLightActor.h>
>
> #include <vtkSmartPointer.h>
>
> #include <vtkRenderWindowInteractor.h>
>
>
> int main()
>
> {
>
>   vtkSmartPointer<vtkRenderer> renderer =
> vtkSmartPointer<vtkRenderer>::New();
>
>
>   double lightPosition[3] = {0, 0, 2};
>
>
>   // Create a light
>
>   double lightFocalPoint[3] = {0,0,0};
>
>
>   vtkSmartPointer<vtkLight> light = vtkSmartPointer<vtkLight>::New();
>
>   light->SetLightTypeToSceneLight();
>
>   light->SetPosition(lightPosition[0], lightPosition[1], lightPosition[2]);
>
>   light->SetPositional(true); // required for vtkLightActor below
>
>   light->SetConeAngle(10);
>
>   light->SetFocalPoint(lightFocalPoint[0], lightFocalPoint[1],
> lightFocalPoint[2]);
>
>   light->SetDiffuseColor(1,0,0);
>
>   light->SetAmbientColor(0,1,0);
>
>   light->SetSpecularColor(0,0,1);
>
>
>   vtkLightCollection* originalLights = renderer->GetLights();
>
>   std::cout << "Originally there are " << originalLights->GetNumberOfItems()
> << " lights." << std::endl;
>
>
> //  renderer->AddLight(light); // can't do this here - must do this after
> the renderWindow->Render() below
>
>
>   std::cout << "Now there are " << originalLights->GetNumberOfItems() << "
> lights." << std::endl;
>
>
>   // Display where the light is
>
>   vtkSmartPointer<vtkLightActor> lightActor =
> vtkSmartPointer<vtkLightActor>::New();
>
>   lightActor->SetLight(light);
>
>   renderer->AddViewProp(lightActor);
>
>
>   // Display where the light is focused
>
>   vtkSmartPointer<vtkSphereSource> lightFocalPointSphere =
> vtkSmartPointer<vtkSphereSource>::New();
>
>   lightFocalPointSphere->SetCenter(lightFocalPoint);
>
>   lightFocalPointSphere->SetRadius(.1);
>
>   lightFocalPointSphere->Update();
>
>
>   vtkSmartPointer<vtkPolyDataMapper> lightFocalPointMapper =
>
>       vtkSmartPointer<vtkPolyDataMapper>::New();
>
>
> lightFocalPointMapper->SetInputConnection(lightFocalPointSphere->GetOutputPort());
>
>
>   vtkSmartPointer<vtkActor> lightFocalPointActor =
> vtkSmartPointer<vtkActor>::New();
>
>   lightFocalPointActor->SetMapper(lightFocalPointMapper);
>
>   lightFocalPointActor->GetProperty()->SetColor(1.0, 1.0, 0.0); //(R,G,B)
>
>   renderer->AddViewProp(lightFocalPointActor);
>
>
>   // Create a cube for the light to shine on
>
>   vtkSmartPointer<vtkPlaneSource> plane =
> vtkSmartPointer<vtkPlaneSource>::New();
>
>   plane->Update();
>
>
>   vtkSmartPointer<vtkPolyDataMapper> planeMapper =
> vtkSmartPointer<vtkPolyDataMapper>::New();
>
>   planeMapper->SetInputData(plane->GetOutput());
>
>
>   vtkSmartPointer<vtkActor> planeActor = vtkSmartPointer<vtkActor>::New();
>
>   planeActor->SetMapper(planeMapper);
>
>   renderer->AddActor(planeActor);
>
>
>   vtkSmartPointer<vtkRenderWindow> renderWindow =
> vtkSmartPointer<vtkRenderWindow>::New();
>
>   renderWindow->AddRenderer(renderer);
>
>
>   vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
>
>       vtkSmartPointer<vtkRenderWindowInteractor>::New();
>
>   renderWindowInteractor->SetRenderWindow(renderWindow);
>
>
>   renderWindow->Render();
>
>
>   renderer->AddLight(light); // must do this after renderWindow->Render();
>
>
>   renderWindowInteractor->Start();
>
>
> }
>
>
>



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