btSoftBody Mysteries

[Herleson]

Hello Friends,

I'm starting some studies about Bullet's soft body simulation. Since the manual has only two pages about it, I started to dive into the demo.

After simulate successfully some soft bodies, some questions arose:

- What is sparseSDF and it's role in simulation? I managed to understand that's kind of a graph, and it's used when a softbody collides.
- What is the "m" parameter in btSoftBody's constructor? All codes that I saw in the demo, its value is zero.
- Is there any way to reduce the size of the shape collision for each node in a mesh?
- What is the default mass of a node in a mesh?

Best Regards!

[Mako_energy02]

I don't know the answers to the first and third question you have. But I can say that the "m" parameter in the soft body constructor is an array for Mass. If left null, the mass for each node in the soft body will default to 1.

[Herleson]

Hello Mako_energy02,

Thanks for the fast reply. It helped me a lot.

Now let's wait for another Bullet Pro explains us exactly what is the sparseSDF struct.

Best Regards!

[Herleson]

Hello Everyone,

I'm still confused about these two questions:

- What is sparseSDF and it's role in simulation? I managed to understand that's kind of a graph, and it's used when a softbody collides.
- Is there any way to reduce the size of the shape collision for each node in a mesh?

Can any Bullet Pro help?

Best Regards!

[majestik666]

sparseSDF for sparse Signed Distance Field is a memory structure
to figure out the distance from the soft body to its environment and
to handle collisions from there, sparse being opposed to a full grid, in this
one the values only exists in a sparse grid to allow faster processing.

Not sure I understand your second question though, what size do you
want to change ?

[Herleson]

Hello majestik666,

Thanks for your answer! It will help me on my studies about Bullet's SoftBody component.

Do you know some references about this data structure and the collision algorithms used by Bullet (Papers, books, sites, etc.)?

The second question is about the size of the AABB shape of each vertice of a mesh. Bullet uses a cube shape for each vertice, and I wish to know if it's changeable.

Best Regards!