Method GetInterpolatedData

IO/Geometry/vtkGLTFDocumentLoader.cxx:1414–1551

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void vtkGLTFDocumentLoader::Animation::Sampler::GetInterpolatedData(float timeValue,
  size_t numberOfComponents, std::vector<float>* output, bool forceStep, bool isRotation) const
{
  // Find the previous and following keyframes
  vtkIdType prevKeyFrameId = 0;

  vtkIdType nextKeyFrameId =
    std::upper_bound(this->InputData->Begin(), this->InputData->End(), timeValue) -
    this->InputData->Begin();

  // If we didn't find the next keyframe, that means t is over the animation's duration.
  vtkIdType numberOfKeyFrames = this->InputData->GetNumberOfTuples();
  if (nextKeyFrameId == numberOfKeyFrames)
  {
    nextKeyFrameId = numberOfKeyFrames - 1;
    prevKeyFrameId = nextKeyFrameId;
    timeValue = this->InputData->GetValue(nextKeyFrameId);
  }

  // Animation hasn't started yet.
  else if (nextKeyFrameId == 0)
  {
    prevKeyFrameId = 0;
    timeValue = this->InputData->GetValue(prevKeyFrameId);
  }
  else
  {
    prevKeyFrameId = nextKeyFrameId - 1;
  }

  // Check if we are on an exact time stamp
  const bool exact = this->InputData->GetValue(prevKeyFrameId) == timeValue;
  // linear or spline interpolation
  if (this->Interpolation != Animation::Sampler::InterpolationMode::STEP && !exact && !forceStep)
  {
    // Normalize t. Set to zero when at the first keyframe, and set to one when at the last keyframe
    float tNorm = 0;
    float tDelta = 0;
    if (prevKeyFrameId == 0 && nextKeyFrameId == 0)
    {
      tNorm = 0;
    }
    else if (prevKeyFrameId == numberOfKeyFrames - 1 && nextKeyFrameId == numberOfKeyFrames - 1)
    {
      tNorm = 1;
    }
    else
    {
      const float prevTime = this->InputData->GetValue(prevKeyFrameId);
      const float nextTime = this->InputData->GetValue(nextKeyFrameId);
      tDelta = nextTime - prevTime;
      tNorm = (timeValue - prevTime) / tDelta;
    }

    if (this->Interpolation == Animation::Sampler::InterpolationMode::LINEAR)
    {
      std::vector<float> prevTuple(numberOfComponents);
      std::vector<float> nextTuple(numberOfComponents);