Documentation/Labs/OpenGLFilters

Here we summarize some efforts for enabling image processing (filtering/smoothing) in VTK/Slicer using OpenGL.

The reason behind this page is trying to coordinate the various projects regarding this subject.

Meetings

9th June 2016

Attended by: Davide Punzo, Jean-Christophe Fillion-Robin, Ken Martin.

In order to implement efficient filtering, OpenGL solution seems the best that fits our needs:

• no requirement on external library (CUDA or OpenCL).
• performance boosting is fairly good to allow almost interactive filtering up to volume of ~10^8 voxels.

Use Case

Based on the Steve Pieper implementation of the classes:

vtkOpenGLTextureImage
vtkOpenGLShaderComputation

here an Use case:

https://github.com/Punzo/SlicerAstro/tree/master/Smoothing/Logic
https://www.overleaf.com/read/jbxxsqtctpgv

Full integration in VTK

For a full integration of the openGLfilters pipeline in VTK, it will be ideal to have a general purpose class:

VTKOpenGLImageAlgorithm

this class will have the duty to:

• handle the I/O communication between the vtkImageData and the GPU Texture using fully the VTK shader infrastructure, since the shader infrastructure is already available in VTK (safe binding, automatic versioning, etc... http://www.vtk.org/Wiki/Shader_In_VTK).
• child classes will handle different approach (e.g. multipass/iterative filtering).

Next steps

• Talk with Steve and getting his feedback.
• Ken will be very happy to contribute a base class vtkOpenGLImageAlgorithm
  • Timeline: in 2-3 weeks after his vacation
  • Most likely derived from vtkImageAlgorithm, the class will integrate feature from VTK/Rendering/OpenGL/vtkGaussianBlurPass.h to facilitate the use of custom shaders to implement GPU based filters.

References

• Developer_Meetings/20150609
• Developer_Meetings/20150901
• https://github.com/pieper/CommonGL/tree/master/GLFilters
• http://www.vtk.org/Wiki/Shader_In_VTK
• VTK/Imaging/General/vtkImageGaussianSmooth.h