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loriwang

Please someone give me some advice

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Hello everyone. I am apologize for my english first because it is not my I home language. I want to write a class to represents a balloon (or it is said bubble - a plastic or rubber ball filled with gas in it). The behaviour is jumping (when it hit something it will be pressed and then jump away). Are there any books or materials I can take a reference? And your advice is helpful. [Edited by - loriwang on February 4, 2008 10:07:16 PM]

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Quote:
Original post by loriwang
Hello everyone. I am apologize for my english first because it is not my I home language.

If english is not your native language, you should be careful with spelling. Things like "plz" and "advz" will make it even harder to understand you, and thereby less likely to try to help.
Quote:
I want to write a class to represents a balloon (or it is said bubble - a plastic or rubber ball filled with gas in it). The behaviour is jumping (when it hit something it will be pressed and then jump away). Are there any books or materials I can take a reference? And your advzs are all helpful.
It sounds like you want not only the physics of a bubble bouncing around, but also the way in which the ball stretches and deforms in response to collisions. Is this correct?

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Original post by Sneftel
If english is not your native language, you should be careful with spelling. Things like "plz" and "advz" will make it even harder to understand you, and thereby less likely to try to help.

Thanks, I will follow your advice.
Quote:
Original post by Sneftel
It sounds like you want not only the physics of a bubble bouncing around, but also the way in which the ball stretches and deforms in response to collisions. Is this correct?

Yes, that is exactly what I want to do.

[Edited by - loriwang on February 4, 2008 10:49:05 PM]

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If you don't need exact physical correctness, I'd advise you to treat those as two separate problems. Making a ball bounce around is a relatively simple task; you just need to keep track of the position and velocity of the ball, and use Euler integration (or something more complex) to move the ball around. As for the deformation, I'd advise you to fake that. Simply detect collisions (and the amount of impulse associated with the collision) and use that to set up a "stretch" animation which plays after the collision. If you want to get more fancy, you could treat the ball as having a smaller radius than it actually does, so that the ball actually flattens against a surface it collides against before bouncing off.

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Original post by Sneftel
If you want to get more fancy, you could treat the ball as having a smaller radius than it actually does, so that the ball actually flattens against a surface it collides against before bouncing off.

But how to deal with a collision between the ball and the point of knife or something like that? (assume the ball is unbreakable) How to present the deformation?

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Original post by loriwang
Hello everyone. I am apologize for my english first because it is not my I home language.


There were some errors, with your English. But, it is not the worst I've seen. You communicated your idea well, I think.

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Original post by loriwang
Quote:
Original post by Sneftel
If you want to get more fancy, you could treat the ball as having a smaller radius than it actually does, so that the ball actually flattens against a surface it collides against before bouncing off.

But how to deal with a collision between the ball and the point of knife or something like that? (assume the ball is unbreakable) How to present the deformation?

That's more difficult, and will require something closer to actual deformable bodies. You may be able to simulate it with a mass-spring system, using a ring of point masses as the "surface" of the ball, pulled together by springs between adjacent particles, yet pushed outward by a force emanating from the centroid of the particles. That should actually get you pretty far, although collision detection might be a bit tricky if you actually want to collide realistically with something as tiny as a knife-point.

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Original post by grhodes_at_work
There were some errors, with your English. But, it is not the worst I've seen. You communicated your idea well, I think.


Oh, thanks for your encouragement. However if someone can points out my errors that is more appreciative. :)

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Original post by Sneftel
That's more difficult, and will require something closer to actual deformable bodies. You may be able to simulate it with a mass-spring system, using a ring of point masses as the "surface" of the ball, pulled together by springs between adjacent particles, yet pushed outward by a force emanating from the centroid of the particles. That should actually get you pretty far, although collision detection might be a bit tricky if you actually want to collide realistically with something as tiny as a knife-point.

I will look for some reference about mass-spring system and to see if I can work out my idear. Thanks for your advice.

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Original post by loriwang
Quote:
Original post by grhodes_at_work
There were some errors, with your English. But, it is not the worst I've seen. You communicated your idea well, I think.


Oh, thanks for your encouragement. However if someone can points out my errors that is more appreciative. :)


Don't worry about it, the errors were small and insignificant. You're polite and appreaciative, something the community often (and should) appreaciates more than simple grammatical/sentence-structural errors.

Best of luck with your project, it's too far above my competence yet so I have no advice, yet. :)

EDIT: A typo, of course.

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