Render Form

Figure 3.20: The Render form

This form is used to create a file with an image of the currently displayed graphics scene. VMD can write input script files for a number of image processing packages. These packages are listed in table 8.1. Once VMD creates an input script in one of the supported formats, the particular package can use this file to create a final output image. See Chapter §  for more information on how rendering is performed.

Rendering

The rendering process works in two stages. The first step writes an input file for the image processing program selected in the Output Formats browser, and the second (optionally) starts the rendering process. The file is given the name entered in the Output Filename field; a default name is given when a new format is selected, so it is best to hold off entering the filename until after the file format is selected. Another way to select the filename is available by pressing the List... button, which opens up a file browser.

Pressing the Go button writes the data file. After that, the Render Command is executed. The default command should start the appropriate rendering program if it is available.

The fastest of the currently supported programs is Raster3D. The rendering command for it has been set up to call the SGI program ipaste when the RGB output file is finished. VMD will wait for the rendering to finish, which causes VMD to freeze, so you may want to run the job in the background. This can be done by enclosing the existing text with ()'s and putting an & at the end. For example, the way to make the Raster3D render command run in the background is:

        (render < %s -sgi %s.rgb; ipaste %s.rgb)&

Caution

There are some issues to consider when using the rendering commands, which can lead to discrepancies between the scene displayed in the VMD graphics display window and the image generated by the image processing application. These issues include:

• The near and far clipping planes are ignored;
• The colors or intensities may be slightly different, due to different colormaps, gamma values, or lighting models;
• The rendering commands do not currently support stereo output, so even if the display is currently in stereo mode, a non-stereo perspective will be used for the rendering program input script;
• Text is generally not available as a graphics primitive in the image processor input scripts, so label text will not appear, although the lines of bond, angle, etc. labels will be drawn. The only exception is in Postscript output, which supports text output.
• Dotted spheres are not drawn with dots.
• The background color may be black, as not all output formats support a background color other than black;
• Cylinders will look slightly different; in VMD cylinders are drawn as cylindrical polygons with N facets, while they may appear as smooth in the final output (which is generally looked upon as an improvement!)