Bullet Physics Hull option not working properly?

[Anonymous]

Hi

I've been looking at the Maya Bullet plugin and am having problems with objects not having the correct collision shape generated by the hull option in the collider properties. As I understand it the "hull" option should be used for objects that have open areas on their surface like a bowl, but when I use that option the collision mesh covers what would be the "top" of the bowl rather than the interior surface.

Is there a way to define the collision shape for the bullet solver rather than using the options in the pull down menu?

Anyone had this before and found a solution?

Cheers

Jim

[sean.heasley]

Hi @Anonymous

Did you use a passive rigid body on your bowl collider? I just made a simply bowl and when I went to add the collider I made sure it was set to mesh and/or compound so the collision box matches the shape of the bowl instead of making a box shape around it which it does by default.

Please let me know if this helps or if you need any more assistance!

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[Anonymous]

Hi Sean, thanks for the reply.

I wanted to make an "active" bullet object, however I also tried the mesh with the "passive" option.

I've included two images of the results.

Basically the "mesh" and "compound" option are the only ones that appear to work properly and then only if the object is "passive". The  collision shapes are all incorrect when I try to generate an "active" bullet object.

So can I force Bullet to use one of the correct collider shapes from the "passive" object set up with an "active" object? 

Note: The passive colliders were generated in the wrong world space unless I first zeroed out the object using bonus tools, a problem I've come accross before with Bullet.

Cheers

Jim

[Anonymous]

...and I also tried with the normals reversed with the same result.

Cheers

Jim

[sean.heasley]

Hi @Anonymous

Thanks for attaching the screenshots!

I see your confusion here but Hull is working as intended. Hull collision is a hull around a mesh that has no concavities. You can think of it as "gift wrapping", where nooks in the mesh are covered by a flat surface distended between the nearby folds instead.

If you want the proper collisions that take up the entire model then you need to use Mesh or Compound like you said in your previous post.

Please let me know if this makes sense or if you need any more assistance!

If one or more of these posts helped answer your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

Kudos are greatly appreciated. Everyone likes a thumbs up!

[RickyODonnell2341]

Hi Sean

Thanks for the reply

OK, so the "hull" option is working as intended, but the "compound" option doesn't work if the object is active and "mesh" is not an option for active objects, so currently I am still not able to generate an active (concave) bullet object with the correct collision shape.

I've tried this on several other simple concave meshes and am getting the same issue.

Cheers

Jim

[sean.heasley]

Hi @RickyODonnell2341

Wait now I'm confused, are you trying to set up the complex collisions for your box or for the bullet?

What kind of mesh are you using as a bullet?

The compound and mesh collisions will work for a non active collider like the bowl.

I just created a basic sphere with an active compound rigid body and then a bowl with a passive mesh rigid body and collisions work as expected.

[RickyODonnell2341]

Hi Sean

What I am trying to do with Bullet in Maya 2017 is to make an active bullet object from a simple concave mesh (polygons).

The only option I can see, is to seperate the mesh into smaller meshes and each smaller mesh has to be a box, sphere, plane or cylinder and then use the compound function.

So would this be the correct process for creating an active bullet object (in Maya 2017) from a mesh containing concave surfaces or one that isn't the same shape as a box, sphere, plane or cylinder ?

Cheers

Jim

[sean.heasley]

Hi @RickyODonnell2341

This is why I'm confused. If you have a complex object you should be able to use the Compound setting to get a collider that accurately matches your con caved mesh.

If that's not working for you, when you get a chance can you post some screenshots or video of what's going wrong on your machine?

If you need a video capturing program, Screencast is a great option that we use here at Autodesk

[sean.heasley]

Hey @RickyODonnell2341

Just wanted to check in to see how things were going. Any changes with this issue?

If your issue is resolved, please click Accept as Solution on the posts that helped you so others in the community can find them easily.