compatible with PoissonRecon

This release contains a version of filter_mrc which has the minimal features to generate an oriented point cloud which can be read and refined by PoissonRecon. PoissonRecon is an implementation of the Screened Poisson Reconstruction algorithm which is useful for automatic closure of membrane surfaces.

Further refinement of the mesh is probably necessary to reduce bulges and make a smooth reasonable looking (minimal-energy) surface. Currently this can be done with the aid of MeshLab. A mesh-voxelizer will be needed if you want to determine which voxels lie inside and outside the membrane. (This has not been implemented yet.)

A brief tutorial for how to extract closed membrane surfaces from CryoEM tomograms can be found (with links to further documentation) here.

While this code works, unfortunately the process is still slow. The entire process of automatically segmenting a closed surface from a membrane requires a similar amount of time and effort compared to manual segmentation.
In the future, some of these external processing tools will either be automated or included with the download and customized for use with CryoEM tomograms. The eventual goal is to make this as automatic as possible.