Control RBD

[A-OC]

Hi all.

I wanna have an RBD setup like this:   youtu.be/yQlh_4dnZfM

which I do, but then I need to be able to set at will this angle, while the simulation is running:

 

For example, start at this angle, 180.  At frame 10 start turning towards 150, at frame 15 lock at 150 degrees.

I tried a combination of hinge and angular constraints but it's not behaving correctly.

 

Edited December 26, 2016 by A-OC

[Atom]

Have you tried basic parenting?

[A-OC]

stick.hip

Oh thanks, that sounded pretty promising, but upon testing a couple scenarios I couldn't make it work.

I'm attaching my basic hip file, hoping you guys could take a shot at it.

What I'm looking for is for it to behave as it had a servo driving the angle:

https://www.youtube.com/watch?v=bu3SPwzcocU

 

Edited December 27, 2016 by A-OC

[rich_lord]

I've wanted to get arvos working well for a really long time. Each time I have a go, I eventually hit a wall.

Here's a simple setup that comes close to working, hopefully someone else can take it from there.

Each arm has a hinge constraint to restrict the orientation axis and pin it to the previous piece.

Each arm also has an RBD Angular Spring Constraint to allow you to set the orientation. On this node you can set a Goal Rotation in world space that should allow you to angle it how you want.

Works great!..... well almost. The RBD Angular Constraint does not allow you to key Goal Rotation. It just uses whatever it finds first and then ignores the rest. So no animation of the servo

Weirdly, if you don't set a goal object, then it does allow you to key it, but very quickly there is fighting between all the objects as all the rotations all want to align to world space.

I've tried a million things, and never been able to solve this satisfactorily. Maybe its time to bug it.

 

 

rl_servo_03.hip

[rich_lord]

YAY!

I stopped being scared and dived inside the RBD Angular Spring Constraint node and worked out how to alter it so that rotations can be keyed. This means animated servo's seem possible with this setup(Though I'm not sure if this is the best method still)

When I dove inside, I noticed that there was an extra parameter not exposed. Rotation. I set that to evaluate always, and created a new parameter on the top level node. Worked a treat. Now you can key rotation and it should work as expected.

Now, how to get it with procedural constraints and packed geo.......

rl_servo_04.hip

[A-OC]

Duuuude ! you're the man !

I was ready to ditch houdini and go straight to a full-code solution!

I'm gonna need a few hours to play with this after work.

Thanks.

Nobody else tried to get servos working before ?
 

 

[rich_lord]

I havent seen much work on this in Houdini. Making procedural robots has always been a goal of mine, but I keep hitting walls when I find time to play around with it. Please post any results you get as I'm very interested!

[A-OC]

Will certainly do. If I get this working you'll shit bricks