Bullet physics

vvvv beta question
1

Hello,

if I create a box with Box2D, it falls down, as expected.

When I use the Bullet physics plugin, the created soft bodies fall down, but the rigid bodies don’t. Does anyone know what I am doing wrong?

I would like the rigid bodies to fall down also, unless I specify that it shouldn’t obey gravity.

2

check mass, kinematic or static body’s won’t fall, it’s priority of active body’s only

3

Kinematic did the trick, thanks.

How should I interpret kinematic then? If I set Kinematic to 1, it doesn’t move at all, it doesn’t listen to ‘linear velocity’. But then I don’t understand the difference between is static, and is kinematic. Static, I would say, doesn’t move at all, but Kinematic sounds to me like ‘it can be moving’ (but it might not obey the laws of gravity).

On What is kinematic in physics? - Answers it says “Kinematics is a branch of classical mechanics which describes the motion of objects without consideration of the circumstances leading to the motion.”

But as far as I can tell for now, setting is kinematic to 1 has the same effect as setting is static to 1, that is, making the object completely inert.

So, I managed to get my rigid body to fall, but I don’t fully understand what the pins do yet…

4

If body is set as static it will never move.

For bodies to be dynamic (eg obey gravity), they need to:

  • have shapes with a mass != 0
  • Not been flagged as static/kinematic

Only way to move a kinematic body is to update it’s position/rotation manually (Using UpdateBody).

Difference between Static/Kinematic is when you update a kinematic body position, the engine will also update it’s velocity, which is quite useful for resolving contacts.

Updating a static body manually can be done, but they are not designed for it, so it will not update it’s velocity, and it can create some odd situations.

5

how exactly does one update the position/rotation of a kinematic body?

regarding the updatebody node:

  • ‘set_position’ doesen’t seem to work after i createrigidbody
  • rotation doesn’t seem to be available at all

do i have to bang other nodes when manual input ?

tx

bullet kinematic q.v4p (42.3 kB)

6

Hey, was fixed actually, but somehow forgot to release.

Will post new version in contribs soon (with few other fixes too).

7

Please see

bullet-physics-nodes-beta

Latest release should fix that.