next up previous contents index
Next: Caveats Up: Scene Export and Rendering Previous: Screen Capture Using Snapshot   Contents   Index

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 8.1 lists the currently supported output formats, and where appropriate rendering software may be obtained.

Table 8.1: Miscellaneous Rendering Options
Name Description
ART$ ^1$ Simple VORT ray tracer
Gelato NVIDIA Gelato PYG Format
PostScript Simple Vector PostScript Output
POV3$ ^2$ POV-Ray 3.x ray tracer
Radiance$ ^3$ Radiosity ray tracer
Raster3D$ ^4$ Fast raster file generator
Rayshade$ ^5$ Rayshade ray tracer
RenderMan PIXAR RenderMan RIB Format, render with Aqsis,
  Pixie, PRMan, RenderDotC
STL Stereolithography format, triangles only
Tachyon$ ^6$ Fast, high quality parallel ray tracer
TachyonInternal$ ^6$ Faster, built-in Tachyon engine that generates images directly
  from VMD internal data structures with no intermediate step
TachyonLOptiXInternal Built-in GPU-accelerated version of Tachyon
  for NVIDIA GPUs (available on supported platforms)
TachyonLOptiXInteractive Interactive, built-in, GPU-accelerated version of Tachyon
  for NVIDIA GPUs (available on supported platforms)
VRML-1 Virtual Reality Markup Language V1.0
VRML-2 Virtual Reality Markup Language V2.0
Wavefront Wavefront .OBJ/.MTL scene format, loads into 3DS Max,
  Blender, Maya, and others
X3D$ ^7$ X3D declarative scene format
X3DOM$ ^8$ Open source HTML5-based X3D viewing system

$ ^1$ Available from along with the rest of VORT package
$ ^2$ See
$ ^3$ See
$ ^4$ See
$ ^5$ See
$ ^6$ See
$ ^7$ See
$ ^8$ See

Making the raster image is usually a two step process, e.g. with the exception of the built-in TachyonInternal and TachyonLOptiXInteractive renderers. 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 external rendering programs typically 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 Targa and let you use the tools listed in Table 8.1 to get what you need. Raster3D, Tachyon, and POV-Ray can produce Targa files, so you don't need to do anything but specify this output format. Rayshade creates RLE image files, which can be converted using ImageMagick. Radiance generates an .oct file, which can be converted with the rview and rpict commands included 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 Tachyon or Raster3D as they are generally the fastest programs. These 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 window, 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 8.1, 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: Caveats Up: Scene Export and Rendering Previous: Screen Capture Using Snapshot   Contents   Index