Terrain ground plane ignored- objects fall through...

[cwalrus]

So weird- 

 

For the first 40 frames of the debris sim, the RBD objects completely ignore the terrain that I selected as the ground plane / static object.

 

Then suddenly at around frame 41, all the objects jump to new positions, and they start to respect the ground plane....

 

Anyone heard of this?

 

I've attached the file but lots of Geo is not attached....
 

 

I should add - it appears to be ignoring the substeps I have cranked up as well (they're at 24) - at least, it ignores them until around frame 41. .... 

 

EDIT- 

I went into the DOP network and everything behaves differently in there - but still ignoring the ground plane!

Dune_Shot03_16.hiplc

Edited February 10, 2016 by cwalrus

[Atom]

Every 3D package has this problem. You can't reliably collide with a paper thin object. Instead of using a grid try using a box or simply extrude your grid down a bit. The initial velocities may be exceeding the z-bounding area of the plane then as velocities settle down they actually can collide.

[cwalrus]

I've suspected that, because of similar experiences in Maya, but extruding the static terrain did not help. 

 

So I've tried:

 

1-increasing substeps

2- increasing  uniform divisions on the static object in the DOP

3- extruding the terrain object

 

and still the debris just flies right through it. 

 

Any other suggestions? 

 

Thank you people

 

EDIT:

 

starting to suspect maybe because I'm using RBDPacked objects of a pre-fractured object, rather than straight-forward RBD objects for my sim....? See file above 

Edited February 10, 2016 by cwalrus

[3iart]

Perhaps it is ignoring it because it isn't there?

 

Have you viewed your collision volume? By default it's a blue color in dops.

 

Perhaps your debris has no collision volume.

 

Try viewing both to verify that they exist.

 

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[cwalrus]

Thanks for that good tip. It does look really odd. Check it out - there are holes / canyons in it:

 

[cwalrus]

On further testing, I can put down either a ground plane, or a grid, and the debris reacts with it correctly. (It doesn't fall through the 'floor'.)

 

But the moment I apply "Mountain" to the grid (to make it match the hi-rez terrain) it loses the ability to recognize the ground as a static object. (and yes, that means applying "Mountain", and THEN making it a static object.)

 

How can I get around this? obviously I need my debris to react with the terrain... is there some setting or mysterious button I'm not clicking?

 

thanks for help!!

[3iart]

You need to think in terms of volumes. just adding a mountain to a grid doesn't make it a volume.

 

You need to find a way to make it "air tight"

 

a simple, but not always effective, solution is to cookie it with a box.

 

You might also turn up your volume resolution.

 

Try creating a sdf iso offset to determine the optimal resolution.

 

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EDIT:

you may also want to limit your geo to the area that is actually being collided with.

Edited February 10, 2016 by 3iart

[cwhite]

Your file doesn't work due to several missing files, including the terrain (e.g. $HIP/abc/terrainReduced.obj). But if you're using the Bullet solver then the parameters on the Bullet Data tab are what you should be experimenting with.

[cwalrus]

Well actually, turning it into a static object does 'make it a volume'  - in that the collision area is calculated by default as "Volume Based Collision Detection" on the Static Object node.

 

Oddly enough, now I've discovered if I add a UV projection to the grid before the mountain, it recognizes it!  What is going on here?

[cwalrus]

Thanks Cameron - Yes I said that in my first post - I have not included all the .bgeo's etc. You can still view the parameters. 

[cwhite]

Thanks Cameron - Yes I said that in my first post - I have not included all the .bgeo's etc. You can still view the parameters. 

 

The volume parameters that you modified on the static object's RBD Solver tab don't have any effect if you're using the Bullet solver. All of the parameters on the Bullet Data tab are still at their defaults, but if your terrain is concave you probably shouldn't be using a convex hull collision shape.

[cwalrus]

Really? Well that could be exactly it! I assumed since it showed me a collision guide on the RBD solver tab it was using that... 

 

But if it is only using that Bullet solver tab that changes everything- and yes, I should change concave to convex. Thanks... stand by....

[cwalrus]

Cameron, you're my hero!

 

Also, all people named Cameron are typically great, I've found.

 

Thanks! That was it!

[3iart]

You can view collision geo in bullet also. The solver determines the type of collision you are using.

Edited February 10, 2016 by 3iart