This plugin reads electron density maps written in the MRC format, also used by the CCP4 suite. More information on this file format can be found in the CCP4 documentation at


This plugin is used only to read files. VMD does not currently support writing this file type.

CCP4 files are created using the native byte-order (i.e., "little-endian" or "big-endian") of the machine used to create them. This plugin can read maps created with either byte-order.

Density values
Only "mode 2" maps (those with density values stored as 32-bit floating point values) can currently be read.

Symmetry Records:
CCP4 maps contain information useful in crystallography, including a collection of records that describe the symmetry of the crystal. Since VMD does not make use of such information currently, these symmetry records are only printed to the terminal when the file is read, and ignored otherwise.