VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Tue Oct 06 2020 - 10:46:04 CDT

Hi,
  You can place objects at a fixed screen location by
purposefully setting the view transformation matrices
for the molecule(s) of interest, and toggling those
molecules (F)ixed in the GUI (or by script commands).
If you're not a computer graphics expert, you may find
calculation of the view transformation matrices to be
a somewhat daunting task, but these are concepts
that are well documented in basic computer graphics
texts, so if you want perfect control over on-screen
placement, that's really the only way to get it.

In general VMD computes the view transforms by computing
an axis-aligned bounding box for the top molecule's contents,
and applying a scaling operation such that it should fit
within the VMD view frustum with typical camera/display
screen height and distance parameters. This auto-scaling
is the main reason that you get varying outcomes for a given
set of coordinates for things like text, even when they are
in their own independent molecule. By setting the transformation
matrices yourself and locking them (making the molecule "fixed")
you prevent the autoscaling behavior from impacting the view.

Best regards,
  John Stone
  vmd_at_ks.uiuc.edu

On Mon, Oct 05, 2020 at 07:39:02PM +0000, Goedde, Chris wrote:
> Hi all,
>
> Is there a way to place text (or other graphics objects) at a fixed (x, y) location on the display, independent of atomic coordinates or the rotation or scaling state of the view?
>
> Thanks,
>
> Chris
> 

-- 
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/