Capability to read/write MRC files
MRC is a file format for imaging data in 3D electron microscopy, where the result of the technique is a three-dimensional grid of voxels each with a value corresponding to scattering potential. It was developed by the MRC (Medical Research Council) Laboratory of Molecular Biology. This file format is supported by many software suites for molecular biology that support volumetric data, such as IMOD and Chimera. The file format is described in http://en.wikipedia.org/wiki/MRC(fileformat), see also http://www2.mrc-lmb.cam.ac.uk/image2000.html and http://bio3d.colorado.edu/imod/doc/mrc_format.txt.
There is an ITK module that contains classes for reading and writing image files in the MRC file format, see http://www.itk.org/Doxygen/html/group__ITKIOMRC.html. Since ITK-based image analysis has previously been made available to ParaView through VTK plug-ins, it is perhaps it is not that hard to add MRC read/write capabilities to Paraview.