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Old 27-12-2006, 12:28 PM   #1
TAZINLWFL
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Question Dynamic Pendulum

I need a little bit of help.

I found an old walkthough (from Maya 2.5 i think)
it shows you how to make a Newton's Pendulum...

It just doesnt work for me...


I've attached the file...

maybe someone can figure it out?

Thanks
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Old 27-12-2006, 12:30 PM   #2
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forgot to attach the file
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File Type: mb pendulum.mb (202.2 KB, 160 views)
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Old 27-12-2006, 02:21 PM   #3
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can you also provide a link to the walkthrough?
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Old 27-12-2006, 02:29 PM   #4
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I've just had a look at your file Tazinlwfl, there's just a few things I noticed and straigtened out.

The ball that was moving initially is off-center. This is helping to cause an unsatisfactory bounce. I also noticed that this ball was rotated some. A quick reset transformations, before moving the ball back to the rest position solved that.

Next, I found that by placing the axis of a sphere at the point of contact between the frame and the two nails suspending it, caused undesirable results. I simply reset the axis to the center of the sphere.

After I'd straightened out the above, there still remained the question of how to get the balls moving. If the axis was left up between where the 2 nails touched the frame, and the ball rotated, it took the right position but was positively useless during simulation.

What I found was that the ball responded to the dynamics simulation much better if the ball was moved into it's initial position rather than being rotated into it.

So, I created a locator, scaled it to make selection easier and then positioned it at the center of the sphere that was to start the animation. I then placed the axis of this locator between where the two nails that suspend this ball touch the frame. I was then able to rotate the locator into a good position to start the animation(45 deg). Then I grabbed the ball, moved it so it's center was v-snapped to the locator. Since the ball was moved and not rotated, I then had to rotate it by the same amount that the locator was rotated by (45 deg).

If I didn't use a locator to position the ball at it's starting position, I couldn't be sure it was the right distance away from the point it was suspended from - meaning that it'd hang higher or lower than it should have.

Simon

EDIT: wondered about a link to the walk-thru, but see that that's since been covered.
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File Type: zip modifiedpendulum.zip (25.4 KB, 118 views)

Last edited by enhzflep : 27-12-2006 at 02:34 PM.
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Old 27-12-2006, 03:13 PM   #5
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It sounds like you have solved it.... thank you...

unfortunately, I am using version 6.5, so I cant open your edited version.

I followed what you did, and did notice the first ball was off-center... (oops)... i reset all locations so that all of the balls are in a line resting (as if it stopped)... now you said to reset the axis, and move the ball to the initial position (not rotate) using a locator as a guide, right?


EDIT:
Did everything... still not working... played with some settings, and it still doesnt seem to work... if you got it to work, which settings did you use?



and the link for the walkthrough doesnt work anymore (from the old alias site)
I found a PDF with it all there... I can share if you'd like...[

Last edited by TAZINLWFL : 27-12-2006 at 03:27 PM.
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Old 27-12-2006, 11:48 PM   #6
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Ah, gad-dammit. Knew I should have saved it as an .ma file.

Hmm. Sorry I've been unclear in my instructions. I've just gone through it all again just to make sure I've not missed a step. So, here's what I did, verbatim.

Fixing Newton's Pendulum

PART I - Align the balls
~~~~~~~~~~~~~~~~~~~~~~~~
1) Load file
2) Using front view, select left-most sphere
3) Modify->Reset Transformations
4) Translate by 5 in Y axis


PART II - Reset axii
~~~~~~~~~~~~~~~~~~~~
1) For each sphere, move the pivot to it's center.


PART III - Setting the start position
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1) Create a locator
2) Set the ScaleX, ScaleY and ScaleZ of the locator
to 1.5 in the channel box. This makes it easier to grab a hold of.
3) Move the locator to the center of the left-most sphere.
4) Move the pivot of this locator directly up
until it is the same height as the top of the frame.
5) Select the locator AND the ball and set RotateZ to -45 deg.
Note: This will make the ball rotate in place and the locator
swing around it's pivot point.
6) Move the already-rotated ball so it's pivot lies on top of the locator
you just positioned(with the -45 deg rotate).
7) Hit play.

Here's the .ma file of the scene. I believe you can edit the file by hand and get maya to open it.
Just change 1/all of these 3 lines to reflect the version you'd like to open it with

requires maya "7.0";
fileInfo "product" "Maya Unlimited 7.0";
fileInfo "version" "7.0";

Simon
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File Type: zip modifiedpendulum_ma.zip (68.2 KB, 70 views)
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Old 28-12-2006, 08:27 AM   #7
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lol....

um...:headbang:

not to be a pain, but i really dont know how to open that file either.... if I import or open directly, it says unknown version 7, and I dont know how to change those 3 lines... (i'm very much a newbie)...

I'd like to learn that too, if you could help.... :bow:

THANKS!!!
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Old 28-12-2006, 08:39 AM   #8
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Wait.... I found it online already!!

You have to open it with a text editor (like Notepad) and the first couple of lines has that info.... i changed it to 6.5... and it opened fine!!!


GREAT!!!


Now.... does the pendulum work like its supposed to.....

....


...


um.... not really.... i'll upload a movie....
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Old 28-12-2006, 08:50 AM   #9
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Movie is attached.... rendered 200 frames...

does yours come out different?
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File Type: zip newtonspendulum.zip (177.4 KB, 69 views)
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Old 28-12-2006, 09:20 AM   #10
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Cool, glad you got that thing with the .ma files sussed. Wouldv'e mentioned that thing with the notepad if I'd realised, sorry.

As for the animation, uh-huh. That's exactly how mine turns out.

What exactly are you after may I enquire? Do you want it so that just the outside two balls fly away from the bunch in the center, or do you want something like what it's doing now, where all of the balls break apart now and then.

If you play with the gravity field you get a different effect, it's currently at 18.6, or double earth's. Setting it to 9.8 gives a slower animation, with less forcefull impacts.

You may find that playing around with the Bounciness, Damping, Static Friction and Dynamic Friction fields of the balls will give you a more pleasing result.

Just shift select all of the balls then edit these fields in the channel box. This way you avoid having to set each attribute for each of the five balls. You just set each one once and all 5 balls are modified simultaneously.

I found a bounciness of 0.95, Damping 0.1, Static Friction 0.1, Dynamic Friction 0.8 gave a result that I liked better.

Now to find that tute and learn more about the rigid solver...

Simon
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