From: Brendan Dennis (
Date: Mon Jan 30 2023 - 20:16:39 CST


I provide research IT support to a lab that makes heavy use of VMD. They
recently purchased several new Linux workstations with NVIDIA RTX A5000
GPUs, which are only compatible with CUDA 11.1 and above. If they attempt
to use the binary release of VMD 1.9.4a57, which is built against CUDA 10
and OptiX 6.5.0, then they run into problems with anything using GPU
acceleration. Of particular note is rendering an image using the internal
TachyonL-OptiX option; the image is rendered improperly, with a severe
checkered pattern throughout.

I have been attempting to compile VMD 1.9.4a57 from source for them in
order to try and get GPU acceleration working. Although I am able to
compile against CUDA 11.2 successfully, the maximum version of OptiX that
appears to be supported by VMD is 6.5.0. When built against CUDA 11.2 and
OptiX 6.5.0, the image checkering still occurs on render, but is not nearly
as severe as it was with the CUDA 10 binary release. My guess is that some
version of OptiX 7 is also needed to fix this for these newer GPUs.

In researching OptiX 7 support, it appears that how one would use OptiX in
one's code changed pretty substantially with the initial 7.0.0 release, but
also that CUDA 11 was not supported until the 7.2.0 release. It
additionally looks like Tachyon 0.99.5 uses OptiX 7, and I was able to
build the libtachyonoptix.a library with every OptiX 7 version <= 7.4.0.
However, there does not appear to be a way to use this external Tachyon
OptiX library with VMD, as all of VMD's OptiX support is internal.

Is there any way to use an external Tachyon OptiX library with VMD? If not,
is there any chance that support for OptiX 7 in VMD is not too far off on
the horizon, perhaps even in the form of a new alpha Linux binary release
built against CUDA 11.1+ and OptiX 7.2.0+? For now, I've had to tell people
that they'll need to make due with using the Intel OSPray or other
CPU-based rendering options, but I imagine that's going to get frustrating
fairly quickly as they watch renders take minutes on their brand new
systems, while older workstations with older GPUs can do them in seconds.

Brendan Dennis (he/him/his)
Systems Administrator
UCSD Physics Computing Facility;!!DZ3fjg!6Pk3uKQJXsVVUBSNiEN5nlGSFRbvhvd-zrWzv6WpfLenvQEvVvxE_ux5Q9DAtJmubWIicqFWxYWVawU-ciHx-3E1Yw$ 
Mayer Hall 3410
(858) 534-9415