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AppGameKit Classic Chat / Do AGK2 physics collisions always get reported as contacts?

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dirahl
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Posted: 2nd Jan 2015 22:29
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I'm creating simple spaceship game, just fly around and shoot the other guy's ship with missiles. I turned bullet physics on for the missiles, and everything seems to work fine..."nearly" all the time. Every once-in-a-while a missile will bounce off the ship (without a player death), or two missiles will bounce off each other. It doesn't seem to matter how fast they are going.

I check for collisions by examining the contact list. In these cases, it doesn't appear that the collisions are being reported to the contact list. I have debug code that reports the full contents of the list.

Is there a good place to go that really explains how the contact list works?

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Funnell7
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Posted: 2nd Jan 2015 23:00
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I don't know the answer to your question, sorry!, but could you not make the missiles sensors (SetSpritePhysicsIsSensor(Spr, 1)? Assuming you are detecting collisions correctly, this should stop any bouncing off...
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swissolo
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Posted: 2nd Jan 2015 23:42
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Be sure to check both A and B of the contact list. Honestly though I believe it may be an AppGameKit bug.

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dirahl
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Posted: 3rd Jan 2015 15:54
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I figured it out. I'm not sure if you'd call it a bug or not. I was using SetSpriteAngle, which apparently doesn't check for physics collisions (not a surprise, since it doesn't have the word "Physics" in it). Therefore, bullets would bounce off the ship any time the player was rotating it during contact. It's not an obvious behavior; clearly the check was done at some level, or the bullet wouldn't have bounced. But the check didn't make it to the contact list, so maybe you'd call that a bug.

Thanks for your responses, though. I've been messing with it for less than a week, so I'm bound to do some dumb things.
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unlikely
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Posted: 4th Jan 2015 00:12
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I had something similar to this happen... I never did figure out what was causing it, but now that you've posted that, it sounds likely. I would call it a bug for sure.
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rfwarrior
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Posted: 11th Feb 2015 20:02
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Aaarrrggghhh.


I've just spent ages trying to debug something similar.

if setSpriteAngle is set on a sprite with physics enabled that object will not report collisions.

So - the question is, can anyone suggest any work arounds?

could I have an invisible sprite that I rotate and allocate the resulting image to the sprite with physics?

I'll see if I can come up with something and will post back if I get it working.
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rfwarrior
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Posted: 11th Feb 2015 20:39
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Okay I've investigated further.

From what I can tell if you use setSpriteangle then collision detection won't work on that sprite for that cycle.

In my code I was setting sprite angle even if it hadn't changed and so no collisions were detected.

so I changed my code to only use setSpriteAngle. that fixed the collision detection, unless I was holding my left or right rotate buttons.

So I changed my code further to only check the rotate buttons every other cycle - I had to change my rotation angle from 2 to 4 to keep the rotation speed the same.

Collision detection is now working flawlessly.

By cycle I mean each iteration round the do /sync loop.

Hope this helps someone.
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