[vtkusers] Problem with color and shading when rendering vtkimagedata

[Aron Helser]

I have no experience with volume rendering in vtk, so my best suggestion is
to look at some of the examples:
https://lorensen.github.io/VTKExamples/site/Cxx/#volume-rendering
and see how the parameters are set there, compared to your code.
You might have success modifying one of the examples to use your data.

On Wed, Dec 12, 2018 at 4:15 PM shadab anwar <sk.shadabanwar at gmail.com>
wrote:

> Hi Aron,
> Thanks for your reply.
> I am not using any specific example.
>
> I am trying to render voxels using imagedata, I have used the above code
> for doing so.
> The problem I am facing is that whenever I rotate the image after
> rendering I don't get proper shading and uniform coloring. Instead, I am
> getting above rendering results, where you can see the few voxels are
> shaded as black!
> I am not able to understand where I am going wrong. I tried changing
> few shading and lighting parameters but no success.
>
> I am a newbie, apology If my problem is too basic!
>
>
> On Wed, Dec 12, 2018 at 4:06 PM Aron Helser <aron.helser at kitware.com>
> wrote:
>
>> Can you be more specific? How do the images differ from what you expect?
>> Is there are particular VTK example you are following that you are trying
>> to change?
>> https://lorensen.github.io/VTKExamples/site/Cxx/
>>
>> Aron
>>
>> On Wed, Dec 12, 2018 at 1:40 PM shadab anwar <sk.shadabanwar at gmail.com>
>> wrote:
>>
>>> Guys,
>>> Waiting for reply!
>>>
>>> Please help!
>>>
>>>
>>>
>>>
>>> On Wed, Dec 5, 2018 at 2:08 PM shadab anwar <sk.shadabanwar at gmail.com>
>>> wrote:
>>>
>>>> Hey amigos,
>>>>
>>>> VTK noob here!
>>>>
>>>> I facing a few problems while rendering vtkimagedata. The code snippet
>>>> as follows,
>>>>
>>>>
>>>>  int X =4, Y=4, Z=4;
>>>>
>>>>        imageData->SetDimensions(X,Y,Z);
>>>>
>>>>        imageData->SetSpacing(1,1,1);
>>>>
>>>>        imageData->AllocateScalars(VTK_INT,1);
>>>>
>>>>
>>>>
>>>>  for (int k = 0; k < Z ; k++)
>>>>
>>>>        {
>>>>
>>>>            for (int j = 0; j < Y ; j++)
>>>>
>>>>            {
>>>>
>>>>                for (int i = 0; i < X ; i++)
>>>>
>>>>                {
>>>>
>>>>                    int* voxel = static_cast<int*>(imageData->GetScalarPointer(i, j, k));
>>>>
>>>>                       voxel[0] = 10;
>>>>
>>>>
>>>>                }
>>>>
>>>>            }
>>>>
>>>>        }
>>>>
>>>>
>>>>  for (int i=2;i!=-1;i--)
>>>>
>>>>        {
>>>>
>>>>        int* voxel = static_cast<int*>(imageData->GetScalarPointer(2,i,i));
>>>>
>>>>         voxel[0]=0;
>>>>
>>>>         }
>>>>
>>>>
>>>>     mapper->SetBlendModeToComposite();
>>>>
>>>>      mapper->SetRequestedRenderModeToRayCast();
>>>>
>>>>       mapper->SetInputData(imageData);
>>>>
>>>>      compositeOpacity->AddPoint(10,1);
>>>>
>>>>       color->AddRGBPoint(10,1,0,0);
>>>>
>>>>      compositeOpacity->AddPoint(0,0);
>>>>
>>>>        color->AddRGBPoint(0,0,0, 0);
>>>>
>>>>        volumeProperty->SetAmbient(0.3);
>>>>
>>>>         volumeProperty->SetDiffuse(0.4);
>>>>
>>>>         volumeProperty->SetSpecular(0.8);
>>>>
>>>>        volumeProperty->SetInterpolationType(0);
>>>>
>>>>         volumeProperty->ShadeOn();
>>>>
>>>>         volumeProperty->SetColor(color);
>>>>
>>>>          volumeProperty->SetScalarOpacity(compositeOpacity);
>>>>
>>>>           renderer->SetBackground(0.5, 0.5, 0.5);
>>>>
>>>>         volume->SetMapper(mapper);
>>>>
>>>>         volume->SetProperty(volumeProperty);
>>>>
>>>>         renderer->AddViewProp(volume);
>>>>
>>>> I am getting the below results,
>>>>
>>>>
>>>> [image: image for forum.jpg]  [image: image for forum2.jpg]
>>>> [image: image for forum3.jpg]
>>>>
>>>>
>>>> It can be seen that everytime I rotate my image I don't get a proper
>>>> shading and color for the object. I have tried changing the lightining
>>>> properties and shading properties but no sucess.
>>>>
>>>> I would be really thankful if anyone could help me.
>>>>
>>>>
>>>> Just for your information I am mechanical engineering with a bit of programming knowledge, so if my question is irrattional please forgive me.
>>>>
>>>>
>>>>
>>>>
>>>> Best,
>>>>
>>>> Shadab
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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