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Higher Quality Rendering

Sometimes images produced by screen capture aren't good enough; you may want a very large, high quality picture, or a picture with shadows, reflections, or high quality rendering of transparent surfaces. While VMD generally produces nice looking images in its graphics window, it was designed to generate its images very rapidly to maximize interactivity, which precludes the use of photorealistic rendering techniques that would slow down the operation of whole program. Instead of producing high quality images directly, VMD writes scene description files which can be used as input to several popular scanline rendering and ray tracing programs. Tables 6.1 and 6.2 list the currently supported output formats, and where appropriate rendering software may be obtained.

Table 6.1: Miscellaneous Rendering Options
Name Description Default Render Command
Raster3D$^1$ Fast raster file generator render < %s -sgi %s.rgb; ipaste %s.rgb
PostScript Direct PostScript Output ghostview %s &
Renderman Renderman RIB Format rgl - Can be rendered with BMRT, PRMan, Maya, etc
STL Stereolithography Format true - Renders Triangles Only
VRML-1 Virtual Reality Markup Language true - view this with VRML viewers like webspace
$^1$See for more info.

Table 6.2: Supported ray tracing formats.
Name Description Default Render Command
Tachyon$^1$ Very fast multiprocessor ray tracer tachyon -mediumshade %s -o %s.tga
POV3$^2$ POV-Ray 3.x ray tracer povray +H500 +W400 -I%s -O%s.tga +D +X +A +FT
Rayshade$^3$ Rayshade ray tracer rayshade < %s > %s.rle
Radiance$^4$ Radiosity ray tracer oconv %s > %s.oct; rview -pe 100 -vp -3.5 0 0 -vd 1 0 0 %s.oct
ART$^5$ VORT ray tracer render < %s -sgi %s.rgb; ipaste %s.rgb
$^1$See for more info.
$^2$See for more info.
$^3$See cek/rayshade/rayshade.html for more info.
$^4$See for Radiance
$^5$Available from along with the rest of VORT package

Making the raster image is a two step process. First you must make a scene description file suitable for the chosen rendering program, and then execute the program using the new file as input to produce the raster image output. The problem is that each of the external rendering programs support different output file formats, which may need to be converted to something more appropriate for you. It is impossible to predict what that might be, so we'll describe how to convert the different file types to RGB and let you use the tools listed in Table 6.1 to get what you need. Tachyon and Raster3D can produce SGI RGB files, so you don't need to do anything but specify this output format. POV-Ray produces Targa files, which can be converted on SGI machines with the program /usr/sbin/fromtarga. Rayshade creates RLE image files, which can be converted on SGI machines with /usr/sbin/fromutah. Radiance generates an .oct file, which can be converted with the rview and rpict commands in the Radiance distribution.

The free program display from ImageMagick - see -
should be able to read and convert between all of these formats.

We suggest using either Tachyon or Raster3D as they are generally the fastest programs. Both programs are easy to understand, and are fast even when rendering very complex molecules.

The generated scene files are plain text so they are very easy to modify. This is most often done to create a larger raster file, though some have other global options which you may wish to change. For instance, by default the Raster3D file turns shadows on. We suggest you consult the relevant renderer's documentation to determine what can be modified in the file.

To actually render the current image into an output file, first set up the graphics in VMD just as you wish the output to appear. Then, either use the Render form, or the following text command, to create the input file and start the rendering program going:

render method filename [render command]

method is one of the names listed in the first column of table 6.1, and filename is the name of the file which will contain the resulting image processing program script. Any text following this will be used as a command to be run to process the file. If %s appear in the command string, they will be replaced with the name of the script file.

next up previous contents index
Next: Known Problems Up: Rendering to Raster Image Previous: Screen Capture Using Snapshot   Contents   Index