Forums > Beginner Poi Moves > The mathematics of a Figure8

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Analemma
Analemma

enthusiast
Location: West LA
Member Since: 22nd May 2003
Total posts: 384
Posted:There are threads about the mathematics of weaves and so on - but try to figure out what is behind this basic little move which forms (next to the circle) the fundamentals of Poi. Its not only the change of sides. Where is the pull (is there a pull?!?), what happens if you play extended/isolated Figure8, what different ways are there to play it, what happens with different Crossover Points . . . .

Ill leave the mathematical aspects to NYC and the aesthetical ones to your imagination smile


ubbloco


To learn - read. To know - write. To master - teach . . .

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Stout
Stout

Pooh-Bah
Location: Canada
Member Since: 12th May 2004
Total posts: 1872
Posted:That's what NYC was saying,,,,today, up until now it was just the 2 dimensional stuff.

What I was suggesting was we first define the shape of the path that one poi traces, which we don't need gravity or air resistance for.

This is one of the beauties of math,,the ability to make assumptions and leave thing out and still end up with a true statement.

We can assume that air resistance is non existent, or constant due to an assumed constant velocity and shape of a poi, we can assume the force of gravity is negated by the force exerted by the spinner. ,,,,for now.

What we need first is the 3 dimensional framework to build on. and I think we have two different equations when we keep the theoretical point of rotation fixed ( by holding your hand rigid..) and by moving the point of rotation back and forth. Try the wire loop model

I've looked around online and I haven't found anything suitable to describe this shape.

As for isolations ( those mad2) I wonder if they wouldn't be described by using a spinning staff as a model.


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NYC
NYC

NYC
Location: NYC, NY, USA
Member Since: 26th Aug 2001
Total posts: 9232
Posted:Ug... OK Kids, stay with me here. And thanks to Cole for trying to explain...

X = cos .5T
Y = sin T
Z = cos (.5T - pi/2)

Can we all agree that:
"NYC has come up with an overlysimplified theoretical three dimentional representaion of the path of a poi head when doing a figure 8"

It looks like a figure 8 from two sides (top and front) and like a circle from one (the side) which the above equations do. XZ is looking from the side in this case. XY and YZ from the front and top.

Gross Oversimplification right?


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Stout
Stout

Pooh-Bah
Location: Canada
Member Since: 12th May 2004
Total posts: 1872
Posted:And there you have it, I wish I had the capability to graph it and I'll look for someone who does.

That equation assumes a single fixed point of rotation right? in the center of the graph.

thank NYC


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Lavatwilight
Lavatwilight

old hand
Location: Wellington somerset, UK
Member Since: 11th Aug 2004
Total posts: 834
Posted:NYC you have/are doing a degree in maths? can i ask you to have a look at somethign for me, in a few months when its finished (all purley theoretical and all) damn shame im not going to uberstaff now

Drawings by chalk minds, strech between the stars

Kyle Mclean-
Contact without dance is like sex without wiggling.
A) it does feel as good
B) it does not look as good on film

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NYC
NYC

NYC
Location: NYC, NY, USA
Member Since: 26th Aug 2001
Total posts: 9232
Posted:No, No and No.
Well, yes on the damn shame about you not going to Uberstaff.

I'm just particularly good at 9th grade math and 10th grade physics. Which is really all you need to understand a figure 8.

Upon further reflection, the hand motion on a figure 8 is identical to the path of the poi, just smaller. It moves left to right using a sinusoidal pattern while making circles in the wheel plane.

Don't believe me? Just do a giant figure 8 and you'll see your hand follow the exact path that the poi would on a regular sized figure 8.

Any beginning poi move can be done by having the hand do a smaller version of the desired move but just 90 degrees ahead of the poi. I could draw force arrows and crap but that would take effort.

Now, before you all get cranky, you don't HAVE to do the complete move with your hand, you can just do a segment of the move and then 'cheat' for the rest of the move. So it feels like you're just 'pumping' at certain times, and you are.

As we get more advanced, that small flick can be applied at any point in the move just to keep the poi moving. But it's always 90 degrees ahead of the poi to achieve maximum pumpage.

For example, when doing a forward butterfly with your right hand (so just the circle) you can simply pump your hand up when the poi is at the bottom of the circle. Remember when it's at the bottom of the circle, it's moving at 90 degrees to that so it's moving left to right.

It'd be pretty easy to design a robot to do a figure 8. Just have one motor go left to right at the same time that another spins.


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Analemma
Analemma

enthusiast
Location: West LA
Member Since: 22nd May 2003
Total posts: 384
Posted:Written by:
X = cos .5T
Y = sin T
Z = cos (.5T - pi/2)




A Riddle:
If you do 2 Figure8s with 2 Poi in Splittime aka a 2beat weave, according to your equation one hand is following the other (I think this is what Z describes?!?)
But for a perfect 2beat weave the handles should rotate around the same spot. One leading, one following. 2 Different Figure8s?!? Can be seen when doing a 2 beat with a staff or meteors.
->
Written by:
the hand motion on a figure 8 is identical to the path of the poi, just smaller.


In general yes, specifially no wink

Where is my mistake confused

hug for the effort

andy


To learn - read. To know - write. To master - teach . . .

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NYC
NYC

NYC
Location: NYC, NY, USA
Member Since: 26th Aug 2001
Total posts: 9232
Posted:Oh easy answer.

When you're doing poi you are powering the poi by doing this "cheat" by staying a little off the center of rotation and pulling at 90 degrees.

When you're doing staff or meteors, it's the rotation of the wrist that powers the tool.

So a staff's center can stay on the center of rotation as long as you're willing to rotate it with your wrist.

And the poi need to recreate the move (or some portion of it) to give it the momentum.

If you could somehow power poi by rotating the wrist (like a club) then you could stay perfectly on the axis.

Any other questions? biggrin


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coleman
coleman

big and good and broken
Location: lunn dunn, yoo kay
Member Since: 29th Aug 2002
Total posts: 7330
Posted:yes - how do you power an isolation?

if your hand is opposite the poi head (which can plainly be seen to be the case), then the 90deg out of phase powering thing can't apply...

i'm thinking it has quite a bit to do with tension but i'll leave it to you to explain smile


cole. x


"i see you at 'dis cafe.
i come to 'dis cafe quite a lot myself.
they do porridge."
- tim westwood

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NYC
NYC

NYC
Location: NYC, NY, USA
Member Since: 26th Aug 2001
Total posts: 9232
Posted:Sure, the center of rotation of an isolation moves a small bit. That center of rotation is 90 degrees out of phase.



So even though the center of an isolation LOOKS like it's not moving, it has to be making a very small circle because it's 90 degrees ahead of the rotation of the hand and wick.


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NYC
NYC

NYC
Location: NYC, NY, USA
Member Since: 26th Aug 2001
Total posts: 9232
Posted:You can see this better as newbies like me and Kael isolate. wink



If you watch Kael's isolation vid you can see a bit of this going on in his buzzsaw isolations.



Again, as we get better we work on disguising that powering 'pump' motion to small flicks which make our circles look prettier.


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coleman
coleman

big and good and broken
Location: lunn dunn, yoo kay
Member Since: 29th Aug 2002
Total posts: 7330
Posted:cool


cole. x


"i see you at 'dis cafe.
i come to 'dis cafe quite a lot myself.
they do porridge."
- tim westwood

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NYC
NYC

NYC
Location: NYC, NY, USA
Member Since: 26th Aug 2001
Total posts: 9232
Posted:I'm surprised that you fellow geeks don't think about this stuff as your spinning, like I do. Maybe I'd be better if I just focused on doing the move, rather than deriving it. wink

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KaelGotRice
KaelGotRice

Basu gasu bakuhatsu - because sometimes buses explode
Location: Angel's Landing, USA
Member Since: 21st Jul 2003
Total posts: 1584
Posted:hehehe I'm a newb again!

I thought I always was one... wink


To do: More Firedrums 08 video?
Wildfire/US East coast fire footage
LA/EDC glow/fire footage
Fresno fire

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