Mark Coyle (coyle++at++dexter.psych.umn.edu)
Wed, 13 Apr 94 17:34:38 +0100
The specifics:
Hardware: SGI 310 VGXT 64 Meg Memory 1 Processor
Application:
I'm lucky in that the entire animation is controlled by me, with
no user input to control the scene. Other than the texture, which
I will get to in a moment, the only objects in the world is a road,
very basic, non-textured and not a performance problem. There are
4 other objects, each of which represents road signs. They will
be placed at about 1/4 mile intervals along the road (basically, you
can only see one of them at a time). These signs are texture mapped
using Designers Work Bench and saved as .flt files. The texture
is put on in the DWB application, so I do no explicit texture
calls in my application program.
The animation simply goes along the x coordinate at a designated speed,
for example 30 MPH, towards the signs.
My frame requirements aren't all that great, I could live with 15 frames/sec,
but not much lower than that.
The problem: I start out fine, going along towards sign # 1 at about
15 frames/second. Once I pass sign # 1, and sign # 2 comes into
view, I can get only 7-12 frames/second. This is the same for the
sign #2 and #3 boundries as well, i.e. the effect is not cummulative
in lowering my frame rate.
What I have done and what I know:
If I make sign#2 the same as sign # 1 (by just loading the same file
2X), I do NOT get the performance degradation. I have done some
profiling of the code, and it seems that when the frame rate is low, both the
CPU usage by sys and GFX (finowt) are much higher. Also, my CPU usage
during those times jumps way up, from about 20% to 80%.
SInce I know exactly what movement will happen, I have set my scene up so
that only the current sign is under the scene root. Once I pass it, I
remove and delete that child, and add the new sign to the scene. This
has some positive effects, but not much.
Am I doing somthing that I shouldn't? Or is there somthing I could do
that I'm not?
I'd like to think I could get at least 15 frames/sec out of this application.
Any ideas?
Thanks
Mark Coyle
HFRL
Computer Science Department
U of Minnesota
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