Joints Extension

Nvm, redownloaded and now it works for the most part. For some reason the dolls knees are revolving the opposite directions. The demo in the dropbox is correct though.

this is outstanding extension! Thanks

Thanks, have been using this alot..

Although seem to have found a bug, unsure if its with the physics or the joints

Imagine a platform, using a line joint, with a -10 to 10 limit, only travelling on the X axis.

When the platform motor is running as a negative speed (platform moving to the left)
Any objects on the platform stay on the platform when it hits the -10 limit.

When the platform motor is running as a positive speed (platform moving to the right)
Any objects on the platform get pushed off the platform at the speed of the motor when it hits the 10 limit.

This also happens on the vertical Y axis, moving up (negative speed motor) the objects stop at the top.
Moving down, positive speed motor, the objects are pushed into the ground at the speed of the motor, less noticeable like this though..

edit:

Further testing seems to suggest its when its pushed into the limit, if the platform has gravity, the gravity pushing the platform down into the Y axis, causes any objects on the platform to be pushed into the platform at the same speed the platform is moving at

edit 2:

In case anyone else has this problem, I just resolved this by setting motor speed to 0 when it hit the limit..

Hi:

I'm using the joints extension to create an octopus with dangling tentacles.  It's basically the same as the ragdoll man in the ragdoll demo. The tentacles are purely for visual effect, they won't do anything else other than hang there.

The problem is that I want the gravity quite high, so that the tentacles hang low instead of "floating". but if I increase the weight of the tentacles (or the gravity in the scene), they start to drag the octopus's head down (even if the octopus's head is not affected by gravity, his tentacles are, and so the joint pulls them all down together).

I can't set the octopus's head to "cannot be pushed" because I need it to collide with some other actors.

If I increase the mass of the octopus's head until it's very high, I start to get buggy tentacle movement.

Any help?

Hello,

Is there a way to set the angle of a revolute joint?

Thank you!

Not on my PC at the moment so cannot remember, but can't you set limits on the joint to set the angle?

Yes

Hello,

Is there a way to set the angle of a revolute joint?

Thank you!

In order to limit the angle of a revolute joint, you need to use two blocks: one which is "enable limit of revolute joint" and then another which sets that limit.

If you don't want the joint to move at all, you need to use a weld joint.

Just bumpity bumping this up:

Hi:

I'm using the joints extension to create an octopus with dangling tentacles.  It's basically the same as the ragdoll man in the ragdoll demo. The tentacles are purely for visual effect, they won't do anything else other than hang there.

The problem is that I want the gravity quite high, so that the tentacles hang low instead of "floating". but if I increase the weight of the tentacles (or the gravity in the scene), they start to drag the octopus's head down (even if the octopus's head is not affected by gravity, his tentacles are, and so the joint pulls them all down together).

I can't set the octopus's head to "cannot be pushed" because I need it to collide with some other actors.

If I increase the mass of the octopus's head until it's very high, I start to get buggy tentacle movement.

Any help?

I wonder whether this would work. Have another actor type, and give it a blank animation the same size of the octopus head. Set that to 'cannot be pushed' and make it a sensor (perhaps it doesn't even need a collision box - I'm not sure). Then, attach all the legs to that actor type. Then, in a 'when updating' event, set the x and y of that type to the x and y of the head. This may work, but if it doesn't (also likely), reply here and I will try to think of something else.

I'm not sure I communicated what I meant, I want to be able to "point" the revolute joint by setting it's angle, as opposed to turning on a motor.
(I'm using this to have a character swing the sword in a combo, and at the end of each move I want to set the angle, so when you do the combo over and over again it doesn't get misaligned.)

Wait, I'll try setting limits and then removing them almost right away...

It worked!

Thanks!

I wonder whether this would work. Have another actor type, and give it a blank animation the same size of the octopus head. Set that to 'cannot be pushed' and make it a sensor (perhaps it doesn't even need a collision box - I'm not sure). Then, attach all the legs to that actor type. Then, in a 'when updating' event, set the x and y of that type to the x and y of the head. This may work, but if it doesn't (also likely), reply here and I will try to think of something else.

I did try that, but it seems that Joints don't work well with "set X to..." blocks (somebody earlier in this thread mentioned that). Thanks for your idea though.

Rather than setting the x and y, could you try, pushing very sharply towards the octopus head?

Rather than setting the x and y, could you try, pushing very sharply towards the octopus head?

I like your thinking. A lot. I'll try that when I'm next dealing with that issue. Thanks!

The link for the box 2d manual in the OP seems to be broken.

Hi,

I'm having difficulty as there doesnt seem to be any documentation/examples? Can anybody give me an example of a puley joint or a revolute joint between two actors?

Thank you!