+2 votes

I have made a rigidbody and it can collide with static body.
However, I have made a several copies of the rigidbody and they don't collide with each other. And the rigidbody can collide with other different rigidbodies.

What's the problem?

Thanks

in Engine by (249 points)

yes, the RigidBody has Concave Polygon Shape.
Does it matter?

I have tried enable Contact Monitoring and set Contacts Reported to 1 but didn't help.
Anyway, thank you.

I am not sure it's intended or a bug.
but, according to my test,
RigidBody with ConcaveShape does not collide to each other.

Convex vs Convex : collide
Convex vs Concave : collide
Concave vs Concave : not collide

I asked godot dev team about this.
it's normal(?) for now about rigidbody collision with these conditions.

Convex vs Convex : collide
Convex vs Concave : collide
Concave vs Concave : not collide

there is -convcolonly option for exporting Convex polygon shape for collision.

http://docs.godotengine.org/en/3.0/getting_started/workflow/assets/importing_scenes.html#create-collisions-col-colonly-convcolonly

Thank you so much.
How to note your comment as answer?

BTW, why it is normal? I don't get the idea why Concave vs Concave : not collide
Is there any reason behind?

Thanks again.

2 Answers

+4 votes
Best answer

Rigidbody collides with each other with this polygon shape.

Convex vs Convex : collide
Convex vs Concave : collide
Concave vs Concave : not collide

There is -convcolonly option for exporting Convex polygon shape for collision.

http://docs.godotengine.org/en/3.0/getting_started/workflow/assets/importing_scenes.html#create-collisions-col-colonly-convcolonly

There should be something need to implement for colliding Rigidbody with Concave polygon shape with each other.

http://kmamou.blogspot.com.ar/2011/10/hacd-hierarchical-approximate-convex.html

It probably will be implemented at 3.1 or later.

by (9,768 points)
selected by

Thank you so much.
But may I ask why the concave do not collide with concave?
Is it harder to implement than convex collision?

Thanks

i am not expert on physics.
but according to document,
it seems to be internal processing to make concave polygon to multiple convex polygon to detect collision.

+2 votes

This sounds like it could be a collision layer/mask issue.

Check out this post for some clarification on how to set these.

by (391 points)

no. The rigidbody is in the same mask and layer. So it should be able to collide with its copies

Have you tried reparenting the collision shape?

The collision shape is direct child of the rigidbody.
Thank you

Can you share a project with us so we can see?

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