[vtkusers] Light source similar to a flashlight?

[Bill Lorensen]

Move the light to 0,0,2 and you will see it. I'm not yet sure why this works.

On Sun, Nov 25, 2012 at 7:13 AM, David Doria <daviddoria at gmail.com> wrote:
> On Wed, Nov 21, 2012 at 11:40 AM, web-Dmitri web-Danewitz
> <d.danewitz at web.de> wrote:
>>
>> Thank you David,
>>
>> It still does not work for me. I made a very small example, explaining my
>> problem.
>>
>> What I expect to see when I shine on the surface is for it to look
>> something like this:
>> http://i.imgur.com/DpH6m.jpg
>>
>> Instead it looks like this:
>> http://i.imgur.com/Wz4ga.jpg
>>
>> But when I just make the surface to be shined on smaller (-5, 5, -5, 5,
>> -5, 5) instead of (-500, 500, -500, 500, -5, 5) it look like this:
>> http://i.imgur.com/Je5BD.jpg
>>
>> Is there a away to make it look like picture 1?
>>
>> Here's the short code used for this example:
>
>
> I can't get this to work either. I have simplified the example by creating a
> plane on which to shine the light. I have placed a sphere at the point that
> the light is supposed to be focused on. I have used a vtkLightActor to
> verify that the light is pointing where we expect. The scene looks correct
> without this line:
>
> renderer->AddLight(light);
>
> but as soon as I add that light, the plane disappears entirely (is black?)
> when viewed from any direction, and the sphere is only visible when viewed
> from the direction of the light.
>
> Can anyone explain what we are doing wrong here?
>
> #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, 1};
>
>
>   // 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->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); // commenting this line shows the plane in
> normal light
>
>
>   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, 0.0, 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();
>
>   renderWindowInteractor->Start();
>
>
> }
>
>
>
> David
>
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