It is also possible to make side-by-side stereo plots, and to plot the screen menu. These options are chosen in the Plot_setup menu. The parameters defining the stereo are in the last few lines of the O meta-file. The way this is done is to display the root object ( disp_all) in the left viewport, then change the point of view slightly, and display it again in the right viewport. The left and right viewports can overlap on the paper, and you may have to play with these values to get things right. The maximum viewports has a dimension of 1 in both directions, so the plotting area is square
viewport 0 1 0 1
Use ghostscript to quickly check things. In the same manner, the Z-thickening can be changed. The Z-thickening is used to create an illusion of three-dimensionality and is determined by the thickness of the slab. Thus, if the object is near the far end of the viewing volume (that is, near the back slab), it will be drawn with thin lines, and if is near the front, it will be drawn with thick lines. The size of the text varies in the same way. You can use the text_size command to adjust the overall size of the text characters, and the slab to adjust the front and back sizes of the letters. Z-thickening can also be adjusted by changing the values using the thick command. There is currently an unfortunate limitation in oplot, which will be changed sometime: the viewing operation is set when an object is displayed. This means that the same Z-thickening is applied to all sub-objects in a composite object. In other words, the disp_bonds object in the O output file, may contain molecules, maps and text, which will get the same Z-thickning parameters applied. The way around this is to display molecule, text and map objects in their individual objects, varying the slab parameter for each according to need.