Editing Ray (section)

==Performance==
*The ray performance depends on distance between camera and molecule.
If the distance is big rendering takes much time. If the distance is too small distant parts of molecule dissolve.
<gallery>
Image:Close_ray.png|Too close to molecule
Image:Middle_ray.png|Normal distance
</gallery>
* Tip: If you have a rather complicated scene that is zoomed into only a part of the molecule, you can speed up the ray tracing by hiding everything else outside of a certain range of the zoomed-on point.  For example, if I have a large molecule and I'm looking only at the 30-atom ligand bound to it, then I can do something like the following:
<source lang="python">
# setup your complex scene
...

# zoom on the hetero atom (ligand and not water) within 5 Angstroms
select hh, het and not resn HOH
zoom hh, 5

# turn on depth cueing
set depth_cue, 1

# now, select stuff to hide; we select everything that is 
# farther than 8 Ang from our main selection
select th, (all) and not ( (all) within 8 of hh) )

hide everything, th

# any additional commands you want
...

ray
</source>
As an example of the efficacy of this method, I ray traced a rather complex scene with all the atoms visible here's the output of ray:
<source lang="bash">
PyMOL>ray
 Ray: render time: 24.50 sec. = 146.9 frames/hour (941.88 sec. accum.).
</source>
and here is the result when I soft-clipped everything else using the above method:
<source lang="bash">
PyMOL>ray
 Ray: render time: 47.93 sec. = 75.1 frames/hour (989.80 sec. accum.).
</source>
The two images in the following gallery show the results of the rendering.
<gallery>
Image:Ray_method_off.png|normal ray tracing.  This took twice as long to make as the image to the right.  Same size, and DPI.
Image:Ray_method_on.png|manually hiding things you won't see anyway.  This took 1/2 the time to render as compared to the same sized & DPId image at left.
</gallery>

===Memory===
If memory is an issue for you in PyMOL, try executing your rendering from a script rather than a PyMOL session file.  An unfortunate unavoidable consequence of the fact that we use Python's portable, platform-independent "pickle" machinery for PyMOL session files.  Packing or unpacking a Session or Scene file thus requires that there be two simultanous copies of the information to reside in RAM simultaneously:  one native and a second in Python itself.

So when memory is a limiting factor, scripts are recommended over sessions.