VMD-L Mailing List

From: Zilong HE (he-zilong053_at_g.ecc.u-tokyo.ac.jp)
Date: Tue Sep 24 2024 - 02:00:00 CDT

Howdy, VMD users and developers,

In a Windows 10 computer with Intel graphics driver, when
displaying atoms as spheres with VDW drawing method, the GLSL rendering
mode in a 32-bit VMD 1.9.3 has been spotted to show two kinds of baffling
artifacts. Although they only affect visual quality in the graphical window
and not in the rendered results using e.g. Tachyon, resolving them is
still good to relieve eye strain a bit.

Under perspective projection, all spheres look very deformed, with at least
two fragmented surfaces intertwining at different angles. Upscaling spheres
with the size parameter or zooming in for a close-up look will make it
worse.

Under orthographic projection, if any material with opacity between 0.5 and
1.0 is selected like Glass2 and Translucent, and the line of sight is not
aligned with the z-axis, then some kind of dark shading of atoms occurs
with noisy, curved, pixelated edges as well as sharp, straight edges. It
makes a dazzling, strobing visual effect when atoms are rotated. The
display settings of near clip and far clip seem to interact with the
shading.

The issues have been posted to another forum as well by a friend of mine
with a methane as example: [external link to image, note the screenshots in
(b) and (a), compared with Tachyon rendering in (d) and (c)]
https://urldefense.com/v3/__http://bbs.keinsci.com/forum.php?mod=attachment&aid=OTgyMDB8NzhjZGNiZmR8MTcyNzE1Mjg4M3w2MDkzN3w0NTg0Mg*3D*3D&noupdate=yes__;JSU!!DZ3fjg!971Xpk8-B3b5YqzfqESdw6HAHODCGsfCUta12GDf3HvQ9DWpijxfHRbh4f29Pljtdu4P4LL7kzA4rqLxSTkUAFJRpfBjcMa31pc$
Neither
of us have enough knowledge about the inner workings of OpenGL in VMD. If
it is okay, we would also like to translate and crosspost useful
information in this discussion to that forum.

Any help is gladly appreciated. Thank you.

Regards,
Zilong