Hi Jason, You can have Chimera print out the density map values used for the slice display in the volume tracer dialog by adding a line to the Python code. Edit file chimera/share/VolumePath/gui.py to add "print values" after the interpolated_values() call: values = data_region.interpolated_values(xyz_list, vertex_xform, use_subregion = True) print values Use the same indentation for the "print values" line as the preceding one since that is important in Python. If you restart Chimera and place a marker on your virus map it will output the array of values to the reply log which you can display with menu entry Favorites / Reply Log. You can copy and paste the values from there. If you just want slices along the x, y or z axes you could get the exact values from the map (no interpolation) by setting the volume region bounds (volume menu Features / Region bounds) to just include a 1 dimensional slice (for example x range 83 83 1, y range 97 97 1 -- ranges are <min> <max> <step>) then open the attached Python script that will print the values for just that region. Tom # Print active volume data values to reply log. from VolumeViewer import active_volume v = active_volume() print v.matrix().ravel()