Strange behavior of the physic engine

Unity Engine
1

hi

currently developing a pool game in unity i reached the state where i have to add effect on the cue ball, i found two ways to do it :

1- use an animation of the cue plus Rigidbody.AddForceAtPosition(vecF, pos.transform.position, ForceMode.Impulse);where :
VecF is calculated by a mathematical equation from the rotation angle of the cue .
pos is a dummy GameObject add as a child object to the cue positioned right near the impact position.

result :
it doesn’t work at all it gives the same result as if i add CueBall.RigidBody.AddRelativeForce((Vector3)ForceV ector,ForceMode.Impulsion); => basic pool play no effect over the cue ball

2- use the cue like in the real world to push the cue ball the physic engine give me some strange behavior :

here’s an example in the real world

and look what happen in unity

thanks for reading, if someone know how to fix neither of the two methods or has a tip to apply effect over the cue ball except does i mentioned above it would be helpful :wink:

2

Its very likely that your setup suffers from incorrect physical materials and rigidbody setups (mass) that cause this.

3

the physic setup is quietly tweaked since with the default setting all balls move and stuck in the left rail : no rebound no friction …etc.

i created my own physical material based on a opensource project how used physX as a physic engine :

http://code.google.com/p/mybilliard01/source/browse/wiki/CoefficientsForBilliardPhysics.wiki

the mass of the cue is set to 1 the angular drag is set to : 0.05 the rest is like the setup in the link above

Edit : the physic project setting is also tweaked

4

He’s trying to apply side english. I.e., he hits the ball on the left/ride side and the ball’s bounce against the pad (but not immediate path) is affected. I made a quick sim using reasonable physics materials, masses, and a capsule tip mesh and English just wasn’t happening “the right way”.

Perhaps accurately modeling a stroke requires more complexity? With a real cue stick, there may be more than one point in contact with the ball, the contact may last longer than one instant/impulse, and the angle may not be 100% straight-on throughout. Depending on your timeline, I might be tempted to cheat! Simply apply a torque to a ball when it’s hit propotional to the force and how off-center the hit was. :slight_smile:

PS - I ran into an issue while attempting to model a billards table. How did you handle this?

http://forum.unity3d.com/threads/67320-Help-my-rigidbodies-have-insomnia!

5

Angular velocity is clamped by default. Try checking the project physics settings and make sure you cranked it up.

6

Hi all

back again :stuck_out_tongue:

i tried different things(new cues different size, trie different ForceMode, tweaking the project physic … etc.) nothing seems to work to only solution i could came up with was to apply AddForceRelative to the ball apply another one when the ball touch another GameObject (except the table) but its apply only when the ball come to sleep state again … (the ball move hit 2/3 rails then the second AddForce is applied )

    void OnCollisionExit(Collision collisionInfo)
    {
        if (collisionInfo.gameObject != GetComponent("table"))
        {
            ball.rigidbody.AddRelativeForce(0, 0, 1, ForceMode.Acceleration);
        }
    }

is there anyway to apply the AddForce methode on the first collision encountred ?

lulz

7

I don’t think you’re making your problem very clear. The cues in your video just look they have too much friction on them. Why would you be using AddForce or AddRelativeForce? Why not put a collider on your pool stick?

8

i used two methods one with the collider on the stick => it gives a strange behavior (second video) not a replica on whats happen in the real world

and another method who use addForceAtPosition(on the ball this time) to simulate the impact point of the cue with the cue ball => again this doesn’t work at all with side kicks (side english)

and finally addForce and AddRelativeForce is for the cue not the ball :wink: in order for the cue to hit the ball i must give it a velocity so i used addForce

hope i was clear :slight_smile: my english is poor so :stuck_out_tongue:

9

Ok, that makes it a little clearer. Can you define what you mean by “strange behavior”? Are you expecting the ball to spin and go towards the direction it’s spinning?

10

what should happend is what on the second (none unity) video (APA Dr Cue …etc.)

but when i try it on unity it give me a different result (last video / second unity video)

basicly when you shoot a ball from the sides it move in straight line when it collide with an object (rails/ other balls) it bounce with additionnel angle to the left or the right (depend on if it was a left side shoot or right one) if you shoot the ball in the center it bounce with no additionnel angle