Break Da Wabbit

[Rafal123]

Check this scene:

http://www.rafal.stnet.pl/wabbit.zip

,and this screen:

http://www.rafal.stnet.pl/wabbit.jpg

Short description is:

I got rabbit which is cutted to few parts and it use GLUE op in DOPs. I use force to move it from table. So it moves, get down - because of gravity - and hits the floor and then the wall - which is dops ground plane. After a collision with wall it sticks to that wall.

Can somebody explain why?

Also I have very strong(IMO) 'glueStrenght' attribute --> 100k, to break the rabbit. Is that normal?

p.s

geez.... and I thought Maya's dynamic engine is advanced stuff... pfffff.... me stupid

[craig]

First of all, your rabbit doesn't have a very good collision volume, which you can see in the Collision tab of the wabbit object, if you turn on "Show Collision Guide Geometry" (it helps to have the viewport in wireframe to see this). I set your Divisions parameter to 30x30x30, and this is much better.

Second, the default density of an RBD Object is 1000 kilos/cubic meter, which is the density of water. So your rabbit weighs over 13,000 kilos! That's why you have to have such large force values. I set the Density to 1 in the Physical tab of the wabbit object.

When you do that, and set the Uniform Force down to a value of -100, you get a reasonable simulation of a rabbit being blown off the table and falling apart as it hits the wall. Though I don't understand your actual question: the rabbit sticks to the wall because you have a uniform force that is much, much stronger than gravity, and so the pieces are held there.

I also set the Internal Glue strength to 100, which works much better. The Glue tab has no effect in this situation, so I set the values in there to the defaults.

Also, I don't see why one surface is a Ground Plane but the other is a box. Why not just use a Ground Plane for both?

Here is my version. Hope this answers your question(s).

(apparently, I have lost the permission to upload files, so I can't put my version here. When that gets sorted out, I'll post it)

[sibarrick]

try zipping the file before posting.... i think that does it

[Rafal123]

First of all, your rabbit doesn't have a very good collision volume,

man... it's your rabbit from your tutorial I found here:

http://www.sidefx.com/index.php?option=com...3857&highlight=

Second, the default density of an RBD Object is 1000 kilos/cubic meter, which is the density of water. So your rabbit weighs over 13,000 kilos!

whooahhh!!! heavy rabbit

When you do that, and set the Uniform Force down to a value of -100, you get a reasonable simulation of a rabbit being blown off the table and falling apart as it hits the wall.

I've changed the settigns to values you suggested but it's still strange. I mean uniform field has keyframed force. So force is negative only for certain frames at the beginning, then it's equal 0. So it should acts as a kind of impulse which pushes rabbit, do I think right?

Though I don't understand your actual question: the rabbit sticks to the wall because you have a uniform force that is much, much stronger than gravity, and so the pieces are held there.

again, but uniform field works only for few frames, so I don't understand. Does this rabbit accumulate velocity??? It works little better when I put, as you suggest, uniform force to -100 but.... I don't wanna -100 coz it looks too slow.

Also, I don't see why one surface is a Ground Plane but the other is a box. Why not just use a Ground Plane for both?

man, don't ask me it's scene from your tut... U put box there as a floor

Thanks for help.

[craig]

I've changed the settigns to values you suggested but it's still strange. I mean uniform field has keyframed force. So force is negative only for certain frames at the beginning, then it's equal 0. So it should acts as a kind of impulse which pushes rabbit, do I think right?

again, but uniform field works only for few frames, so I don't understand. Does this rabbit accumulate velocity???

No, that isn't the problem. The problem is that although you are animating the force, you have the parameter set to "Set Initial" - so the value is set to -200000 and then your animation to 0 is completely ignored. Set the parm to "Set Always" and you'll get something much more like you expect.

Sorry, I completely missed that the first time!

That, and the fact that the DOPs tutorial creates the ground box. Whoops!

[Rafal123]

hey Craig, thanks for info