Collision detection using particles

[ame]

I'm trying to use particles as collision detection. I can render the particles as spheres, but the collision detection occurs at the centre of the sphere. Is there any way that I can make the whole sphere detect the collision, instead of just the centre, as in a bounding sphere?

[msimon]

Sounds like you might need a custom script for that one. I know a work-around for one individual particle per particle object, but I don't think that's what you need. I would try finding the scripts (if their even in there) in the Maya script files that have to do with particle collision, and see if some type of distance from particle center variable exists and can be changed. Also, check out the mel documentation dealling with particle collision. Another approach might be to have an invisible surface that the particles collide with offset exactly the particle radius from the visible surface you want them to appear to collide with. Just an idea.

[jtk77]

I know there is a way to expland an objects bounding box in 2.5 but I'm not sure if you can do that on a per particle bases. --Maybe you can make your collition object's bounding box a little bigger and see if the particles read that as their collition. to get the right look .
--ps can't spell don't try .

"Wow! How'd you do that! That looks like somthing out of a movie!"
--some guy at work .

"Wow! How'd you do that! That looks like somthing out of a movie!"
--some guy at work .

[ame]

There is this object class MBoundingBox that takes in two parameters to specify the corners. However, I'm not sure how to use the class objects. And if I'm not mistaken, the bounding box is a read-only value and I couldn't edit the value. Do you know how to expand the bounding box, like you said?

And thanks for the idea on using an invisible surface to give the illusion of collision with the actual, smaller object. May consider using that if there's no easier way of doing it.

Thanks again for all your tips, msimon and jtk77.

[jtk77]

You can change the bounding box , I don't know if it will effect the particles collition , but to make the box around an object bigger in Maya 2x go to the objects attributes , under object display there is Bounding Box settings(min.max settings) try it and post if it changes where that particles hit at all . I'd try it out but I can't even look at Maya right now ...think i hurt my eyes ..

"Wow! How'd you do that! That looks like somthing out of a movie!"
--some guy at work .

[ame]

Ya, I did try that. It's a read-only attribute. The boxes are all greyed out. By the way, I'm using Maya 2.5. Are there any settings I have to do to make it editable?

Another thing is that, I have this expression that rotates a joint about the Z-axis. So, whenever contact occurs ( using the particles for collision detection), the joint will be locked(intended). This is done using the particle collision event procedure, which runs a mel script to lock the joint.

When I run the animation, the joint is locked when the particle detects a collision, but it will still rotate, ie. the locking has no effect. I rotate it manually when it's locked and it won't rotate(which is correct). So, how come?