Method UpdateClippingPlanesBuffer

Rendering/WebGPU/vtkWebGPUPolyDataMapper.cxx:1726–1789

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void vtkWebGPUPolyDataMapper::UpdateClippingPlanesBuffer(
  vtkWebGPUConfiguration* wgpuConfiguration, vtkActor* actor)
{
  if (this->GetNumberOfClippingPlanes() == 0)
  {
    // Release any previously allocated buffer
    if (this->ClippingPlanesBuffer)
    {
      this->ClippingPlanesBuffer.Destroy();
      this->ClippingPlanesBuffer = nullptr;
    }
    return;
  }
  if (this->GetNumberOfClippingPlanes() > 6)
  {
    // we only support up to 6 clipping planes.
    // this is a limitation of the shader code and the way we handle clipping planes.
    // if more than 6 clipping planes are needed, then we need to use a different approach.
    // for now, we just log a warning.
    vtkWarningMacro(<< "Too many clipping planes: " << this->GetNumberOfClippingPlanes()
                    << ", maximum is " << 6);
  }
  this->ClippingPlanesData.PlaneCount = std::min(this->GetNumberOfClippingPlanes(), 6);
  vtkMTimeType planesMTime = 0;
  for (vtkTypeUInt32 i = 0; i < this->ClippingPlanesData.PlaneCount; i++)
  {
    planesMTime = std::max(planesMTime, this->ClippingPlanes->GetItem(i)->GetMTime());
  }
  if (planesMTime < this->ClippingPlanesBuildTimestamp)
  {
    // no need to update the clipping planes buffer, it is already up to date.
    return;
  }
  // create a wgpu buffer for clipping planes if not already created.
  if (this->ClippingPlanesBuffer == nullptr)
  {
    const auto label = this->GetObjectDescription() + "-ClippingPlanesBuffer";
    wgpu::BufferDescriptor desc = {};
    desc.label = label.c_str();
    desc.mappedAtCreation = false;
    desc.size = vtkWebGPUConfiguration::Align(sizeof(this->ClippingPlanesData), 16);
    desc.usage = wgpu::BufferUsage::Storage | wgpu::BufferUsage::CopyDst;
    this->ClippingPlanesBuffer = wgpuConfiguration->CreateBuffer(desc);
  }
  vtkNew<vtkMatrix4x4> modelToWorldMatrix;
  std::array<double, 3> scale = { 1, 1, 1 };
  std::array<double, 3> shift = { 0, 0, 0 };
  for (vtkTypeUInt32 i = 0; i < this->ClippingPlanesData.PlaneCount; i++)
  {
    double planeEquation[4];
    actor->GetModelToWorldMatrix(modelToWorldMatrix);
    this->GetClippingPlaneInDataCoords(modelToWorldMatrix, i, planeEquation);

    // multiply by shift scale if set
    this->ClippingPlanesData.PlaneEquations[i][0] = planeEquation[0] / scale[0];
    this->ClippingPlanesData.PlaneEquations[i][1] = planeEquation[1] / scale[1];
    this->ClippingPlanesData.PlaneEquations[i][2] = planeEquation[2] / scale[2];
    this->ClippingPlanesData.PlaneEquations[i][3] = planeEquation[3] + planeEquation[0] * shift[0] +