Re: OpenGL Display List under OS X
Re: OpenGL Display List under OS X
- Subject: Re: OpenGL Display List under OS X
- From: Steven Langer <email@hidden>
- Date: Thu, 3 Jul 2003 10:29:28 -0700
Message: 3
Cc: email@hidden
From: Geoff Stahl <email@hidden>
Subject: Re: X11 and OpenGL drawing together in one window
Date: Wed, 2 Jul 2003 11:17:49 -0700
To: Robert Cox <email@hidden>
On Wednesday, July 2, 2003, at 11:08 AM, Robert Cox wrote:
We have an brain surface visualization program that uses OpenGL to
render the surfaces. The user can draw a region-of-interest (ROI) on
the projected surface. During the mouse movement part of the drawing,
the program just draws (with XDrawLines) over the user's trace. When
the user releases the mouse button, then the surface is re-rendered
with the ROI properly shaded, colored, etc. This dual method is for
speed - we can't render the surface fast enough to keep up with mouse
movements (about 300,000 triangles - takes about 0.25 s to redraw on
my iMac, 0.20 on my PowerBook).
I suspect this can be improved drastically. I have a 300,000 polygon
model that animates very smoothly. You should look to display lists
for static data or vertex array range or vertex array object for
dynamic data (see <http://developer.apple.com/opengl> for more info on
these extensions).
---
Geoff Stahl
3D Software Engineer
Apple
I have an OpenGL application that uses display lists because my users
frequently want to rotate a scene around after it appears. If you run
the program across the network using glx (i.e. OpenGL commands moved
across the network by X11), the display list is transferred once and
subsequent rotations only have to send a coordinate transformation
across the network. This yields highly interactive cross-network
applications without using extensions like server-side vertex arrays
(in this context the server is the machine where you are viewing the
scene).
I have run my program on various flavors of Unix, Linux, and Windows
and never noticed a significant difference in performance between
direct rendering and using display lists when running locally.
When running under OS X, display lists are roughly half as fast as
direct rendering. I discussed this issue with John Harper
<email@hidden> and it appears that this performance issue has
nothing to do with the X11 server - it seems to be an issue with the
underlying OS X OpenGL implementation.
At this time I have to recommend using direct rendering for programs
running locally on a Mac, but I would still use display lists for
cross-network programs.
Steve Langer
email@hidden
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