Subject:
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Re: rotating models in MBC 0.4.1d Cocoa
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Newsgroups:
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lugnet.cad.dev.mac
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Date:
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Wed, 23 Jul 2003 20:23:49 GMT
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Viewed:
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1634 times
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In lugnet.cad.dev.mac, Andrew Allan wrote:
> > What seems to happen is that during the rotation my computer decides
> > to try to render the whole model instead of continuing with the low
> > complexity rotation.
>
> This is a problem I've been wrestling with since I commenced with Objective-C.
> Normally to engage slow drawing mode what I do is I time the redraw operation by
> using glFinish(). This command is supposed to prevent the application from
> continuing until all OpenGL commands have been executed. It works fine in
> classic and carbon environments, however in cocoa it doesn't appear to work at
> all, since control appears to be returned to the program instantly.
I'm not sure I completely understand the above. What are you timing? If you
are just timing how long the glFinish takes, then a change in its behavior might
not be indicative of a bug in the new OpenGL drivers. And if you time how long
you have spent since the same point in your rendering loop from the previous
frame, then it really shouldn't matter if the glFinish is working properly.
Your program shouldn't be allowed to get ahead by more than a single buffer
swap, so at most you should be one frame late in realizing that the redraw is
slow.
Note that I haven't done any Cocoa OpenGL programming, but if you want to know
how long it takes to draw a single frame, you generally need to grab a single
time reading for each frame, and just compare the current one to the last frame.
Taking a reading at the "beginning" and "end" of the frame can lead to less
predictable results. Of course, for the first frame, you have to take your
initial reading at the beginning of the frame, because you have no previous
frame to judge against.
--Travis Cobbs (tcobbs@REMOVE.halibut.com)
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Message has 1 Reply:
 | | Re: rotating models in MBC 0.4.1d Cocoa
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| Travis, To date I have used this apporach in both C and Objective-C: The mouse drag subroutine on the first loop through saves the current system time in a global variable. An event is then sent to initiate redrawing of the model. The the model is (...) (21 years ago, 23-Jul-03, to lugnet.cad.dev.mac)
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Message is in Reply To:
| | Re: rotating models in MBC 0.4.1d Cocoa
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| (...) This is a problem I've been wrestling with since I commenced with Objective-C. Normally to engage slow drawing mode what I do is I time the redraw operation by using glFinish(). This command is supposed to prevent the application from (...) (21 years ago, 23-Jul-03, to lugnet.cad.dev.mac)
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