Higher Quality Rendering
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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 and 8.2 list the currently
supported output formats, and where appropriate rendering software
may be obtained.
Table 8.1:
Miscellaneous Rendering Options
Name
Description
Default Render Command
Gelato
NVIDIA Gelato PYG Format
rgl – High quality GPU-accelerated rendering
PostScript
Simple Vector PostScript Output
ghostview %s &
Raster3D
Fast raster file generator
render < %s -sgi %s.rgb; ipaste %s.rgb
RenderMan
RenderMan RIB Format
rgl – Render with Aqsis, Gelato, Maya, RenderDotC, PRMan
STL
Stereolithography Format
true – Renders Triangles Only
VRML-1
Virtual Reality Markup Language V1.0
true – View with VRML viewers like webspace
VRML-2
Virtual Reality Markup Language V2.0
true – View with VRML viewers like webspace
See http://www.bmsc.washington.edu/raster3d/
for more info.
Table 8.2:
Supported ray tracing formats.
Name
Description
Default Render Command
Tachyon
Very fast, high quality multiprocessor ray tracer
tachyon -aasamples 2 -mediumshade %s -format TARGA -o %s.tga
POV3
POV-Ray 3.x ray tracer
povray +H500 +W400 -I%s -O%s.tga +D +X +A +FT
Rayshade
Rayshade ray tracer
rayshade < %s > %s.rle
Radiance
Radiosity ray tracer
oconv %s > %s.oct; rview -pe 100 -vp -3.5 0 0 -vd 1 0 0 %s.oct
ART
Simple VORT ray tracer
art %s 500 650
See http://www.photonlimited.com/
for more info.
See http://www.povray.org/
for more info.
See http://www-graphics.stanford.edu/ cek/rayshade/rayshade.html
for more info.
See http://radsite.lbl.gov/radiance/HOME.html
for Radiance
Available from ftp://gondwana.ecr.mu.oz.au/pub
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 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 http://www.imagemagick.org/
– 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 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
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.
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Up: Scene Export and Rendering
Previous: Screen Capture Using Snapshot
