View Full Version : Need Help! Objects Not Colliding

01 January 2011, 07:19 PM

Im having a major issue trying to get some bouncing balls to bounce down stairs, this is a project for my course and have been struggling for three days now.

I have managed to get the balls to bounce on certain parts of the stairs but there are a couple where the balls land and go straight through the step. It really is frustrating, i have looked through several threads and done what they have suggested; decreasing step size, increasing collision tollerance and increasing damping on both the balls and the steps but none seem to make a difference. Some were suggesting to look at the normals to check if they are facing the correct way, i dont know how to check this but assume they are correct as the steps were duplicated and some of them work

Really any help is greatly appreciated guys

01 January 2011, 09:37 PM
Can anyone help?

01 January 2011, 10:03 PM
Increase the tesselation value on the geoConnector (the number of triangles the stairs are evaluated with during collision testing). Also, if that isn't enough, set oversampling to something above 1 (2-4 should do the trick).

01 January 2011, 10:43 PM
thanks for the reply man, im having a bit of trouble trying to find the geo connector property, if you could help it would be great. Sorry, im just very new to Maya

01 January 2011, 11:08 PM
Select the stairs and in the attribute editor there should be a tab called geoConnector1 or some other suffix number.

Or, you can select the stairs and graph input/output connections in the hyperGraph panel. You should see the geoConnector there.

Or, you can select the particles, and in the attribute editor there should be a tab called geoConnector1 or some other suffix number.

OH, btw, hehe are you using particles, rigid Bodies or nCloth?

The collision object might have a node connected called nRigid (if you're using nCloth).
Sorry, I just assumed you were using particles....

If you're using rigid bodies, in the script editor, type:
ls -typ "rigidBody"
You will have the names of all rigidBodies in the scene returned. One of the is your stairs collision object.

Or, select your stairs object and run:
string $sel[] = `ls -sl`;
string $shapes[] = ` listRelatives -type "rigidBody" $sel[0]`;

01 January 2011, 11:10 PM
lol that might be the reason why i can't find this, sorry i should have specified, I am using active rigid bodys for the balls and passive rigid bodies for the stairs. This was the only way I knew at the time so if there are any better ways that would help


01 January 2011, 11:28 PM
Thanks alot pixelranger I will give that a try

01 January 2011, 11:36 PM
Are you using maya's built in rigid bodies? That may be your trouble right there. Try using Dynamica or PullDownIt. It'll sim much faster and be much more accurate.

01 January 2011, 12:54 AM
like the earlier post suggested increase the poly count in your stairs as "old school" rigids collide at the verts. if your still having issues then increase your subsampling to a higher value than 1. Mayas rigid bodies suck but are more then capable of simulating this.

01 January 2011, 01:13 PM
Yeah calibrix, I have looked into the dynamica plug in for maya, cant find many tutorials on using it but I will try this out today aswell.

Thanks Mandark I will try this out if I can't get dynamica to work, though its probably pretty straightforward.

01 January 2011, 12:38 PM
Hi Guys

I have posted this subject on the bullet forums aswell, but thought if I could get any help here also it would be good, I have got the balls going down stairs now but the animation isn't accurate at all at the moment, ive fiddled around with some of the options such as mass and friction but the balls just don't seem to bounce.

Another problem is that the animation plays so damn fast, it literally takes 200 frames to finish the animation so I dont have a chance to view the animation properly

If you guys can help it would be greatly appreciated

edit: Just so you guys know what sort of movement I am talking about, I was inspired by the Sony Bravia advert and would be great to get close to this kind of bounce

01 January 2011, 01:54 PM
To solve this problem (like in youtube video) you need nParticles with ball form preset.
because the RBD to simulate approx. the 100 million bulbs you have not come out, and do not need it.

02 February 2011, 12:35 PM
thanks for the reply, cant make out some of your message, I guess you are trying to recommend Particles instead of rigid bodies, if I had alot of time, I would be happy to try this but unfortunately I dont and have invested alot of time experimenting with the rigid bodies.

Anyone else have any suggestions?

02 February 2011, 05:28 PM
nParticles in maya 2009 and above i think. They have self collide properties that can do an ok job of faking rigid bodies especially if your object is a sphere. If you are using maya 2009 or above look into nParticles. As for time spent on rigid learning..the learning curve and the time needed to simulate nParticles is WAY lower.

good luck

02 February 2011, 11:05 PM
yeah mandark thanks for the advice, nParticles seems to do exactly what i need, thanks to all you guys

02 February 2011, 01:01 AM
You can get it to work without nParticles but you need to add divisions ot the stairs and then if the ball is really just a ball you can set it's Stand In to sphere on it's rigidbody.

The geoconnector mentioned earlier I think only applies to particle collisions so that's why you'd have to add divisions. Basically if the divisions in the colliding surface are spaced wider than the diameter of the ball then it will pass through the surface unless it happens ot touch a vert.

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