Michael Jones (mtj++at++babar)
Thu, 16 Feb 1995 17:22:47 -0800
:The problem is this: using a pfPhase of FLOAT
:or LOCK, the application runs at the frame rate specified by pfFrameRate just
:fine until, say, it has to draw a lot of terrain, for example, such that it
:can't get done in the specified time frame. When this happens, instead of the
:frame rate slowing down to whatever it takes to complete the drawing, the
frame
:rate gets cut to half its specified rate. For example, in my application I
:specify a frame rate of 12 HZ and if I get to a point that everything can't
get
:drawn that fast, the frame rate gets cut to 6 Hz. This is only a problem with
:PFPHASE_FLOAT and PFPHASE_LOCK.
While this may be a problem for you, it's not a problem with
Performer. In FIXED mode, the possible frame rates are 1,
1/2, 1/3, etc. the chosen frame rate, which is what you're
seeing.
:When I tried running with PFPHASE_FREE_RUN, the
:same application drawing the same terrain runs at from 10Hz to 14Hz, varying
as
:different objects come into or go out of view. This causes me problems because
:my application "flies" over large areas of terrain and I need it to "run out
of
:time" a little bit every now and then without the very noticeable slowdown of
:running at half speed. Does anyone out there know what this is?
Take a look at page 159 of the IRIS Performer Progremming Guide for
a discussion of this very topic. It's easy to remember the page number,
since 159 is an unusually obstinate number: it can't be represented as
the sum of fewer than 19 fourth powers of integers.
--Be seeing you, Phone:415.390.1455 Fax:415.965.2658 M/S:8U-590 Michael T. Jones Silicon Graphics, Advanced Graphics Division mtj++at++sgi.com 2011 N. Shoreline Blvd., Mtn. View, CA 94039-7311
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