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AppGameKit Classic Chat / Using StepPhysics breaks physics forces

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Yaro
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Posted: 27th Jun 2015 23:43
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I recently tried using StepPhysics(1.0/60.0) to make my game deterministic, but when I do objects I used to move with SetSpritePhysicsForce no longer work. When I comment out the StepPhysics line it works correctly. Objects that I move with SetSpritePhysicsImpulse still work as intended. Has anybody encountered this problem before? Is there a work around?
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baxslash
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Posted: 28th Jun 2015 10:40
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StepPhysics is called internally anyway during the Update2D call. Does the same thing happen if you use Update2D? If not it could be there is a bug in StepPhysics...

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Markus
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Posted: 28th Jun 2015 12:54
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it works, but this stepphysics must behind this command.


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Yaro
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Posted: 29th Jun 2015 02:14
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Thanks Markus, moving it to the end of the frame made it work! Not sure if it should be treated as a bug or if it should just be documented that it needs to be called after forces/impulses.
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baxslash
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Posted: 29th Jun 2015 09:47
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I'm not sure why creating forces and impulses would not work after calling stepPhysics as they should just be applied during the next loop... can you provide example code?

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Impetus73
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Posted: 29th Jun 2015 10:04
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I guess there is a rendering pipeline, that flushes after every physics sync, in the physics system?

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Did Amiga / AMOS programming in the 90's.
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baxslash
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Posted: 29th Jun 2015 11:07
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Quote: "I guess there is a rendering pipeline, that flushes after every physics sync, in the physics system?"

Yes but if he is applying the forces after StepPhysics then I would expect the force to be applied next time StepPhysics is called... unless something in the general Sync or Update does it. That's why I would like to see an example to try to track the bug down.

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Impetus73
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Posted: 29th Jun 2015 13:16
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I just think it would be best to always call all the sync commands at the very end of the loop, with the sync() command last.

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Did Amiga / AMOS programming in the 90's.
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Yaro
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Posted: 1st Jul 2015 05:14
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I tried to isolate it but then it wasn't working at all even when I did it right before the sync. I got kind of deep in some refactoring since this, after I clean that up I'll try to get something usable.
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Paul Johnston
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Posted: 1st Jul 2015 17:56
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Sync was accidentally clearing forces even when it didn't call StepPhysics itself. I'll change this for the next version so forces will only be cleared once, after the physics has been stepped.
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baxslash
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Posted: 1st Jul 2015 20:29
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Awesome thanks Paul!

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