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Pull an object
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 Re: Pull an object
Posted by Livett on Fri Jan 21st at 4:50pm 2005

I am making a kind of cross between a catapult and a trebuchet.

I have it set up so that the arm is being held down by a rope, and you can pull a lever to which deactivates the length constraint and causes the arm to swing upwards because of the counter weight.

I need to make it so that another button pulls the arm back down to it's original position to be reloaded with ammunition. I have tried just turning the length constraint back on but it pulls the arm back to it's original position so fast that smashes into the floor and falls off it's hinge.

So any ideas on how to slowly pull an object back into posisition?





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 Re: Pull an object
Posted by Rof on Fri Jan 21st at 5:00pm 2005

I'm not sure about phys_lengthscontraint, but I think that phys_spring can take an input that can set it's length.

So you could add a phys_spring that's is usually turned off.
Then when it comes to reset the catapult, turn on the spring, and gradually shorten it (using multiple outputs and the "delay" field to make the spring gradually shorter over ~30 seconds or so).
That should make it pull the arm more smoothly, and the fact that it's a spring should make it less abrupt, anyway. (You might want to turn the "force only on stretch" spawnflag on, that should prevent the arm oscillating.)

Then when the spring has pulled back the arm, turn on the phys_lengthconstraint again, and turn off the spring.

You'll probably have to play with the timing and the spring constant, friction, etc., to make it look good.
[addsig]



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 Re: Pull an object
Posted by Livett on Fri Jan 21st at 5:03pm 2005

I will give that a try now



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 Re: Pull an object
Posted by Livett on Fri Jan 21st at 5:08pm 2005

The spring can't be turned on or off. Also it couldn't pull the arm back down.





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 Re: Pull an object
Posted by Dred_furst on Fri Jan 21st at 5:14pm 2005

try getting a phys_thruster to push the catapault back down, then re-enable the constraint when the phys_thruster hits a trigger.
[addsig]



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 Re: Pull an object
Posted by Rof on Fri Jan 21st at 5:23pm 2005

Hmm. You could set the spring length to be really long to turn if "off" (that way, as long as you have "force only on stretch" on, it won't interfere with the catapult operation).

And you might have to set the spring constant to a really high value to make it pull a heavy object. F = -kx, and all that.
[addsig]



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 Re: Pull an object
Posted by Nickelplate on Fri Jan 21st at 6:26pm 2005

keep your original setup only add a spring that pullsthe trebuchet upwards. then the spring should let the end down slowly enough that It wont bust off the hinge. [addsig]




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