[no subject]

Thanks,
Serguei

-----Original Message-----
From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf
Of Bradley Gabe
Sent: October 19, 2006 2:14 PM
To: XSI(at)Softimage.COM
Subject: RE: Motion along a specified vector

Ah yes, the good old wheel problem.

One way I like to solve this one is to ignore the local axis vector
altogether! Instead, it's very easy to use global space and plot a curve
that represents total distance traveled. Then you can set up an
expression that relates the distance being traveled to the wheel's
circumference.

Here's a function that plots a distance traveled. Just input an
X3DObject:

function BG_PlotDist(obj)
{
	// Find or add "Distance" property
	prop = obj.properties('Distance');
	if(!prop){
		prop = obj.AddProperty('CustomProperty', false,
'Distance');
	}

	// Find or add "sum" parameter
	param = prop.parameters('sum');
	if(!param){
		param = prop.AddParameter3('sum', siFloat, 0, 0, 100000,
true);
	}
	
	// Get scene settings
	Play = Dictionary.GetObject('PlayControl');
	sF = Play.In.value;
	eF = Play.Out.value;
	iter = 1;

	// Store Fcurve data in an array
	valArr = new Array();

	// Calculate global distance traveled
	sum = 0;
	var i=0;
	for(var f = sF; f<=eF; f+= 1/iter){
		
		// Grab current global pos
		pos0 = XSIMath.CreateVector3();
		obj.Kinematics.Global.Transform(f).GetTranslation(pos0);
		
		// Grab global pos from last frame
		pos1 = XSIMath.CreateVector3();
	
obj.Kinematics.Global.Transform(f-1/iter).GetTranslation(pos1);
		
		// Subtract last pos from current pos to get velocity
		pos0.SubInPlace(pos1);

		// Add length of vel to sum
		sum += pos0.Length()
		valArr[i++] = f
		valArr[i++] = sum
	}
	param.AddFcurve2(valArr, 20);
}	



> Thanks for the helps guys!
> I will read up on vector projection and will give it a try.
> 
> And yes I am aware that I will not get the full value. I am working on
a
> wheel and basically I only want to register the movement that takes
> place along the direction (vector) that the wheel is pointing at.
> 
> Thanks,
> Serguei
> 
> -----Original Message-----
> From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On
Behalf
> Of Thomas Helzle
> Sent: October 19, 2006 7:20 AM
> To: XSI(at)Softimage.COM
> Subject: Re: Motion along a specified vector
> 
> Hi Serguei,
> 
> but you are aware that you will not get the "full" value of the
> movement? (that would be the vector length of the change itself)?
> 
> For you case, you will have to project the movements vector onto your
> "value-vector" and then compute the resulting vectors length.
> 
> BTW. Since there were a lot of questions regarding vector math lately,
I
> want to recommend the following book:
> "3D Math Primer for Graphics and Game Development"
> http://www.amazon.com/exec/obidos/ASIN/1556229119/thomahelzlges-21
> (watch the line wrap)
> It does a very good job in explaining vector and matrix math from a
> beginner to intermediate level, with really fun and clear examples and
> methodology.
> 
> A very good online ressource can be found here:
> http://chortle.ccsu.edu/VectorLessons/vectorIndex.html
> 
> Best regards,
> 
> Thomas Helzle
> 
> 
> 
> 
> On Thu, 19 Oct 2006 00:06:07 +0200, Serguei Kalentchouk
> <serguei.kalentchouk(at)ubisoft.com> wrote:
> 
> > Hey all,
> >
> > I am trying to find a way to isolate motion along a specified
vector?
> >
> > What I would like is to transform something in x and y and get a
value
> > of how much it moved along a vector that I specify.
> >
> > Any help would be much appreciated.
> >
> >
> > Cheers!
> >
> >
> > Serguei K.
> >
> > - Ubisoft Cinematics -
> >
> >
> 
> 
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