Process hardware cliping using implicit function

xxyyy159 · May 31, 2022, 5:49am

vtkAbstractMapper provides a function,SetClippingPlanes, to cut the actor at hardware level,which might be several magnitudes faster. But I can’t set implicit function to it to get specific shape like below.

    vtkNew<vtkImplicitBoolean> boolean;
    boolean->SetOperationTypeToIntersection();
    boolean->AddFunction(p1);
    boolean->AddFunction(p2);
    boolean->AddFunction(p3);
    boolean->AddFunction(p4);

If there are any methods to do so please let me know.

mau_igna_06 · May 31, 2022, 9:33am

Please check this out:

github.com

Kitware/VTK/blob/6ec7669b382808d91d75d97be715b732e1cf3510/Rendering/VolumeOpenGL2/vtkOpenGLGPUVolumeRayCastMapper.cxx#L1325

      
        
                for (; i < 32; ++i)
                {
                  cropFlagsArray[i] = 0;
                }
            
            
    prog->SetUniform1iv("in_croppingFlags", numberOfRegions, cropFlagsArray);
              }
            }
            
            
//------------------------------------------------------------------------------
            void vtkOpenGLGPUVolumeRayCastMapper::vtkInternal::SetClippingPlanes(
              vtkRenderer* vtkNotUsed(ren), vtkShaderProgram* prog, vtkVolume* vol)
            {
              if (this->Parent->GetClippingPlanes())
              {
                std::vector<float> clippingPlanes;
                // Currently we don't have any clipping plane
                clippingPlanes.push_back(0);
            
            
    this->Parent->ClippingPlanes->InitTraversal();
                vtkPlane* plane;

xxyyy159 · June 1, 2022, 6:25am

I post a gif below to to show the result that the implicit function with four planes cuts a piece of mass out of a sphere.
And I tested the function you provided with the same planes, nothing was left in the renderer, much the same with what I experienced before.
want

mau_igna_06 · June 1, 2022, 7:58am

Maybe you need to create your own shader for this class
https://vtk.org/doc/nightly/html/classvtkOpenGLPolyDataMapper.html

I guess you would need to give different scalar values to the inside and the outside regions

Edit:

I’m not sure you can achieve want you want with a a mapper.
Unless you are rendering a tetrahedral mesh maybe.
Maybe you want to use a vtkClipPolyData and a vtkAppendFilter, but I’m not sure if it will work at the end

xxyyy159 · June 2, 2022, 4:09am

That’s pretty hardcore for me. I’m looking for a solution to process cliping faster than vtkTableBasedClipDataSet with 10 milions of cells rendering together and dynamically updating the result after per cliping.