From: Ryan Hoffman (
Date: Fri Jan 03 2014 - 16:32:14 CST

My understanding about ray tracers in general is that the resulting colors are due to interactions between 'material' and 'lighting' settings. So a red apple under a green light source looks black. But maybe this is some other kind of user error, or maybe even a bug.

What system is this on? Were the binaries pre-compiled?

I'll play for a few more minutes and get back to you.

From: Hoy, Robert []
Sent: Friday, January 03, 2014 14:27
To: Smith, Tyler
Cc: Ryan Hoffman;
Subject: Re: vmd-l: Issues with tachyon internal renderer

Hi, Ryan. It's not a lighting issue -- the colors are completely different, and "right" in Snapshot" but "wrong" in Tachyon. Besides the TCL scripts, would you also like us to send you some PSF/PDB files, or anything else?

Thanks a lot for your help!


Robert Hoy
Assistant Professor of Physics
University of South Florida

On Jan 3, 2014, at 5:24 PM, Tyler Smith <<>> wrote:


On Fri, Jan 3, 2014 at 5:07 PM, Ryan Hoffman <<>> wrote:
Can we see some of the resulting Tcl script? Maybe a lighting issue?
From:<> [<>] On Behalf Of Tyler Smith [<>]
Sent: Friday, January 03, 2014 12:19
Cc: Robert Hoy
Subject: vmd-l: Issues with tachyon internal renderer

Hi All,
     I'm attempting to create a movie in vmd that shows how the local crystallization of a system of polymers evolves with time during quenching. A metric for local crystallization called the CCE norm was used to assign every monomer in the system a crystalline structure ( HCP, FCC, fivefold, unordered). Psf files were used to convey information about the crystalline structure using dummy variables; for example, all monomers with mass < .2 correspond to monomers with FCC ordering and are colored red. Every psf file gives local crystalline structure for one timestep in the quench, so in order to create a movie of evolving crystalline structure a new pair of psf and pdb files needs to be loaded in for every frame. As far as i know vmd can't internally create movies with multiple psf files, so I decided to render a series of bitmap images using vmd and then string them together using another program.

     A c++ program was used to create a long .tcl script that loads in the pdb and modified psf, colors the monomers accordingly, renders an image and then repeats for the next pair of files. This process worked well using the snapshot renderer, but I would prefer to generate higher quality images using Tachyon Internal. When the Tachyon Internal renderer is employed images are rendered but they are not colored correctly.

  Does anyone have any ideas as to why snapshot works and TachyonInternal doesn't? I'll attach the c++ scripts used to generate the .tcl scripts

     Also if there is an easier way to create movies with multiple psf files and custom coloring please let me know.