Author Topic: Collision Trouble  (Read 2911 times)

Offline AGP

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Collision Trouble
« on: May 04, 2014, 02:02:12 am »
I'm trying to have my character collide against walls without getting stuck or ever going through them. The following code is problematic. My question is broad, I know, but maybe I'm doing something wrong...

Code: [Select]
     private SimpleVector collide(SimpleVector directionToHead) {
silmaria.collisionObject.setVisibility(true);
SimpleVector direction = hero.get(0).checkForCollisionEllipsoid(directionToHead, new SimpleVector(.15f, 2f, .15f), 5);//.5f, 2f, .5f), 5
silmaria.collisionObject.setVisibility(false);
if (directionToHead.x != direction.x || directionToHead.z != direction.z) {
     collidedThisFrame = true;
     float multiplier = -2f;
     if (currentAnimation == WALKS)
multiplier = -3.5f;
     direction.x = multiplier*directionToHead.x;
     direction.z = multiplier*directionToHead.z;
}
else collidedThisFrame = false;
return direction;
     }

Offline EgonOlsen

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Re: Collision Trouble
« Reply #1 on: May 04, 2014, 01:08:21 pm »
You world setup seems to suffer from some "tiny scale syndrom"...with an ellipsoid this small, chances are that floating point errors and inaccuracies add to up to some jittering or similar problems. You might want to increase the size of everything. If that's not possible, try to adjust Config.collideEllipsoidThreshold to a lower value and see if that helps.

Offline AGP

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Re: Collision Trouble
« Reply #2 on: May 26, 2014, 11:23:51 pm »
I'm going to play around with this tonight. You seem to have approved the idea of making a World.getFullBounds() or some such method (for informing us, in world units, the size of our scenes). Have you gotten around to making this?

Also, for that soccer test I'm making, how do I get the direction in which the player kicked the ball (the exact direction of the collision with which to translate the ball)?

Offline EgonOlsen

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Re: Collision Trouble
« Reply #3 on: May 27, 2014, 08:13:44 pm »
No, i haven't done anything like that yet. To be honest, i forgot about it.... ::)

About the direction...i'm not sure. I don't think that this really relates to a normal collision detection. I would rather implement it as part of the game physics, which in case of a soccer game, i don't feel to be covered by a "simple" 3d collision detection.

Offline AGP

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Re: Collision Trouble
« Reply #4 on: May 27, 2014, 08:26:41 pm »
OK, let's say I do it as part of the game physics. How could I even get the direction of the kick (maybe that's more of a Bones question...)?

Offline AGP

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Re: Collision Trouble
« Reply #5 on: May 27, 2014, 11:35:03 pm »
I didn't mean the direction that the player is facing, by the way. I meant the direction his foot is going at the moment of the collision.

Offline EgonOlsen

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Re: Collision Trouble
« Reply #6 on: May 27, 2014, 11:46:23 pm »
OK, let's say I do it as part of the game physics. How could I even get the direction of the kick (maybe that's more of a Bones question...)?
I would simply try to approximate it. He will always kick into the same direction (relative to his body) or doesn't he?

Offline AGP

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Re: Collision Trouble
« Reply #7 on: May 27, 2014, 11:52:45 pm »
Always the same direction is fine. But how could I differentiate between different kicks if not by the angle of the collision (which, I suppose, would be a function of the distance between the player and the ball).

Offline EgonOlsen

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Re: Collision Trouble
« Reply #8 on: May 28, 2014, 04:13:21 pm »
Yes, something like that. Maybe based on the angle between the player's direction and the direction vector from the player to the ball or something like this.

Offline AGP

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Re: Collision Trouble
« Reply #9 on: June 16, 2014, 07:48:15 am »
I'm having two collision-related problems in the soccer game. The first one is a huge performance hit. The second one is that I made it so that when the player walks up to the ball a force is added to the ball in the direction in which the player is headed. It works for the first couple of times but if I keep running in the ball's direction I will eventually go through it.

By the way, the crowd's transparency looks horrible in hardware. The following texture (first frame of several, obviously) looks far from opaque:


Offline EgonOlsen

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Re: Collision Trouble
« Reply #10 on: June 16, 2014, 05:33:43 pm »
What kind of performance hit? Who is colliding with what and where does the performance drop happens?
About the texture: Setting it to a higher transparency value should fix this (try 100 or 200 for example).

Offline AGP

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Re: Collision Trouble
« Reply #11 on: June 21, 2014, 12:48:12 pm »
I think that the performance hit actually took place when I switched to hardware, not with the collision, after all. Now that I'm calling compileAndStrip() on everything, I'm getting distinctly better (if still mediocre) performance.

By the way, what kind of a hit could I expect if I disable mipmapping for all textures (and there's a couple of dozen at 1024x1024)?

Offline EgonOlsen

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Re: Collision Trouble
« Reply #12 on: June 21, 2014, 01:32:53 pm »
Depending on the mesh's complexity, it might help to use an OcTree for collision detection (not rendering).

Offline AGP

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Re: Collision Trouble
« Reply #13 on: June 22, 2014, 02:42:32 am »
What about my mipmapping question?

Offline EgonOlsen

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Re: Collision Trouble
« Reply #14 on: June 22, 2014, 11:07:19 am »
Hard to tell....it might go from a pretty big hit to none at all. It highly depends on the hardware and the bandwidth available to the GPU.