expressions question 2004-05-25 - By stefan@(protected)
Back
well... I did a few test to try and get this "wheel" to be
moving. And the expression that came out was:
Fc + ( cylinder.kine.global.posx * 360.0 ) / ( ( 2.0 *
cylinder.cylinder.radius ) * PI ) * -1.0
But if the "wheel" stops (no translation X), it's still
spinning. And it's not rotating correctly. I tried to add
more decimals (ex. 360.0000) which it rounded down to what
you see. So it's not moving correctly. But if I move it
manualy in realtime it rotates correct.
So, anyone knows why? Or how would the expression be
correctly written?
Best regards
stefan andersson
p.s. the cylinder is rotated x=90 to get it standing up
alex dinnin <adinnin@(protected)> wrote:
> Thanks everyone for your help !!!
>
> Got it working a treat now !!!
>
> Alex
>
> Graham D Clark <mail@(protected)> wrote:
> use getBBox to get the geometries min max values as
diameter then use that
> value as diameter in the line where you apply your
expression,
> or if you need the radius to animate over time (and the
object has been frozen
> or has no radius parmeter) then afaik you'll need to make
a scop for it.
> it gets a little trickier if you want to 'steer' your
wheel too and have it
> roate correclty in any direction but animating the wheels
on paths and using
> path percentage value to rotate can make that math a lot
easier
> -- ---- ---- ---- ---- ---- --
> http://www.grahamdclark.com
> 2nd hand TD
>
> -- --Original Message-- --
> From: owner-xsi@(protected)
[mailto:owner-xsi@(protected)] On Behalf Of
> alex dinnin
> Sent: May 25, 2004 12:40 PM
> To: XSI@(protected)
> Subject: Re: expressions question
>
>
> Am I correct in saying then, that if you have frozen the
object !!! you can not
> use the radius ???
>
> thanks for the help on this everyone....
>
> Peter Twardo <peliosis_v2@(protected)> wrote:
>
> Well, since the amount of rotation, depends on both :
translation, and radius
> of an object, your expression could't work.
>
> I hope this helps:
>
> (Try changing radius of your cylinder or whatever if you
havent frozen it)
>
>
>
> ' ******************************************
>
> CreatePrim "Cylinder", "MeshSurface"
>
> Rotate , 90, 0, 0, siAbsolute, siParent, siObj, siX
>
> ResetTransform "cylinder", siCtr, siRot, siXYZ
>
> InspectObj "cylinder.kine.local"
>
> AddExpr "cylinder.kine.local.rotz"
>
> SetExpr "cylinder.kine.local.rotz",
>
"cylinder.kine.local.posx*-(360/(2*PI*cylinder.polymsh.geom.cylinder.radius))"
>
> ' ******************************
>
>
>
> Peter
>
>
>
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