Nat, PyMOL's ray-tracer is pretty simple -- it just divides 3D space up into equally sized boxes, so that ray-intersection and identification calculation can be performed rapidly. The smaller the boxes, the fewer the number of partial geometries will be present in the box.
Hash_max is a hint to the ray tracer about the maximum number of subdivisions it should allow on each axis. In principle, the amount of RAM used is a 3rd-order function of this value. However, the ray-tracer will often use less RAM than that for a variety of reasons. PyMOL usually ships with hash_max set to 100, since that is reasonable for a machine with 256 MB of RAM. 300 is about the highest I've tried, and you could easily require over a Gig of RAM for a situation like that. However, there is definitely a point of diminishing returns, which depends on scene complexity, total number of pixels, etc. Typically each ray-tracing scene will have a different optimum, but usually 140-180 gives the shortest overall rendering times. Cheers, Warren -- mailto:war...@delanoscientific.com Warren L. DeLano, Ph.D. Principal Scientist DeLano Scientific LLC Voice (650)-346-1154 Fax (650)-593-4020 > -----Original Message----- > From: pymol-users-ad...@lists.sourceforge.net [mailto:pymol-users- > ad...@lists.sourceforge.net] On Behalf Of Nat Echols > Sent: Sunday, October 05, 2003 2:28 PM > To: pymol-users@lists.sourceforge.net > Subject: RE: [PyMOL] Pymol script screenplay > > > By the way, you can also use extra RAM to speed up ray-tracing > > by 2-3 fold if you set hash_max to 150-200. > > Wait, I'm curious - what does this command do, and what are the limits? > For a machine with 2GB of memory, what can I get away with? Will I have > problems if I run multiple invocations of PyMOL at once? > > -Nat > > > > ------------------------------------------------------- > This sf.net email is sponsored by:ThinkGeek > Welcome to geek heaven. > http://thinkgeek.com/sf > _______________________________________________ > PyMOL-users mailing list > PyMOL-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/pymol-users
