VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Thu Mar 31 2016 - 10:19:22 CDT

Hi,
  Depth of field is sampled when antialiasing samples are taken, so
the way to achieve a smoother depth of field bokeh effect when doing
batch ray tracing for movie rendering is to crank up the antialiasing
samples significantly, e.g.:
   render aasamples TachyonLOptiXInternal 256
   render aasamples TachyonInternal 256

You can similarly get higher quality AO lighting by cranking up the AO
samples, but Tachyon and TachyonL-OptiX both use a scheme where AO samples
are taken during shading of every ray-object first-hit intersection, so
the AA sample count and AO sample count are effectively multiplicative.
By default, VMD tells Tachyon and TachyonL-OptiX to use 12 AA samples
per pixel, and 12 AO lighting samples per-hit. So that should help you
determine what settings you prefer when rendering your movies.

I should also warn you that if you're using the TachyonL-OptiX GPU ray tracer
to render high resolution movies with very large sample counts, you may want
ensure that your NVIDIA driver configuration has the "interactive" flag
set to "false" so that long running GPU ray tracing kernels (over 2 seconds)
don't trigger the X-Windows server's application termination scheme,
here's a snippet from xorg.conf as an example:

Section "Device"
    Identifier "Device0"
    Driver "nvidia"
    VendorName "NVIDIA Corporation"
    BusID "PCI:2:0:0"
... you get the idea...

    # prevent OptiX timeouts
    Option "Interactive" "false"
EndSection

Let me know if you have further questions.

Cheers,
  John Stone
  vmd_at_ks.uiuc.edu

On Thu, Mar 31, 2016 at 08:27:50AM -0400, Kyle Mills wrote:
> Hello,
> I'm trying to use depth-of-field (DOF) in TachyonOptiX renders using the
> movie maker, and I can't figure out how to modify the number of DOF
> samples to get a smooth image.A The default blur is rather grainy, and
> I'd like to increase the DOF samples...say with a command like
> render dofsamplesA TachyonLOptiXInternal 30
> Thank-you for the help,
> Kyle 

-- 
NIH Center for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
http://www.ks.uiuc.edu/~johns/           Phone: 217-244-3349
http://www.ks.uiuc.edu/Research/vmd/