2 times 45degree Cardial Joint ---- SOLUTION

[k-arts]

Hit there Geniuses,



front view


top view

I tried and tried, but I cannot fix this!!!

The GOAL:

When i start animate rotating one site the other end should rotate as well.
But, important is that the blue boxes and the middle yellow part should rotate in the correct physical direction.
It is logic, but i tried it with constraints and expressions.
It simply does not look good.

If no one knows a solution maybe somebody knows a place or link concerning these physical problems in 3D Studio Max?

If there is any more needed information pls ask..

--> Here is the File for testing http://www.K-Arts.de/FTP/90d Transfer Knee.zip

Thank u very much

.::. Lisa :P

[J_Bug]

I couldn't open your file so I just recreated it quick.

It really depends on what the final animation needs to be and how dynamic you want it but if you arrange your pivots properly you can just animate something like this by hand. Here's an example, which could also be wired to function from a dummy rotation.

www.dtoxx.com/J_Bug/45x2DegRot.max

For a more dynamic solution I will usually create a basic animation of it's functionality and then try to break each part down for wiring by adding dummies where needed. The rotations of these objects are continuous due to a P-Curve Out-Of-Range Type Relative Repeat.

Does this level work for what you're trying to animate? If not maybe a good base to start from

Let me know if you need further explanation on how to wire it and I'll try to take some time later to work on it.

A better forum for getting more answers to things like this might be the Discreet support site.

--Jon

[k-arts]

Keyframe Animation

Hi thanks for ur time...

But check the small movie how it should work.
The three parts are moving seperatly.

RIGHT CLICK AND SAVE THE QUICKTIME MOVIE

It is much more complicated!!

Thx for ur answer!!!!

SOSOOOSOSOOO Lovely

[J_Bug]

Let me think about it but now that I can see that animation I'd say that the two blue cube like hinges which have 2 axis of freedom are rotating equally on each axis but just slightly offset in time. It would take a while to figure out exactly what's happening but let me ask someone here at work who deals with mechanical linkages. This seems like a common setup so he may know the extents of the mechanics.

I'm sure MAX can do this in the end but what your looking for would be better suited for an application like Unigraphics. Can you get the file from the animation you linked to? Where did that animation come from?

--Jon

[J_Bug]

After asking around I've found that it's just two "Universal Joints" like a 4x4 would have. You could find what relative angle for each axis of the two blue links is at a certain rotational values of the entire joint and then keyframe and let MAX find the in-betweens through linear interpolation. By viewing the Quicktime you have... Zero, 45, 90, 180 degrees should all place the blue links in a specific pose that you can recreate by rotating them incrementally to match. As you do this you can record what these rotational changes are and then apply them through an expression.

On another note, If you don't need the overall spline angle to change from 90 degrees then you really don't even need an expression, just hand animation.

Hope it helps Let me know how it comes out. Wish I could help more.

--Jon

[k-arts]

Hi there,

Thx for the responses.

I made the animation by keyframes. The problem ... it is a part of a very big complex machine. And i dont wont to spend too much time for animating it.

!!! Each box is affected by TWO different rotational forces. HOW could an expression handle this?

How could i apply an expression like that?

thx
LISA

[RErender]

I think it might be possible with reactor but I think the way the pins intersect in your model would be a problem, maybe if you changed that... I spent a few hours last night trying to do it with an IK solver it was close but I couldn't get the constraints quite right, I'll probably keep trying ( I love a challenge). Let you know if I get something

[k-arts]

thx cool

btw if u really come close.

Maybe u share ur file so i can get a look at it or someone else to attach the last thought

greets

[SEANT]

One quick note which may influence how this mechanism would be animated (it certainly influences how a universal joint behaves in reality). On a single universal, the output doesn't reproduce the input with perfect fidelity. The angular velocity of the output varies through a 360 degree rotation, and the magnitude of this variation is directly related to the included angle.

These acceleration-deceleration pulses can be negated in the final output by pairing two universals together, but the joints must be shifted 90 degrees with respect to each other. That 'shift' is shown in the QT movie but not the model above.

I don't know if these pulses could influence an animation project much, but they do disrupt mechanism enough for car manufactures to avoid them in favor of CV (Constant Velocity) Joints for use in FWD vehicles.

Sean

[losbellos]

I'll jump in as well, interesting

[losbellos]

So I've made it that it works without constarits, straight.
But for keepeng the angle, somehow I have to limit the rotation, only to the right axis. This I dont know how to do it riht this moment but if u can handle that, I'll send you the max file. But I'll try it also.

See the video what I mean, it works in any situation, even on high speed rotation, if dont use too high acceleration..

www.freeweb.hu/losbellos/test.avi
(divx) 640*480