Documentation/Labs/OpenGLFilters

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Overview

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, Utkarsh Ayachit and Robert Maynard

Based on an original idea of Steve Pieper


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.

2016.06.09 SlicerAstro CPU-vs-GPU Filtering.png
Source: Finding faint HI structure in and around galaxies: scraping the barrel (Astronomy and Computing accepted)



Use Case

Based on the Steve Pieper implementation of the classes:

vtkOpenGLTextureImage
vtkOpenGLShaderComputation

here an Use case:

https://github.com/Punzo/SlicerAstro/tree/master/AstroSmoothing/Logic
https://arxiv.org/abs/1609.03782

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).

Ken Martin provided this structure in VTK: [1]

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.

Status

  • Ken wrote the base class for operation filtering on GPU [2]
  • and he gave also an example how to use it: [3]
  • An application of the class for filtering can also be found here: [4]

References