// $Id: interpxyz.hoc,v 1.2 2005/09/10 23:02:15 ted Exp $
/* Compute xyz coords of nodes in a model cell 
   whose topology & geometry are defined by pt3d data.
   Expect sections to already exist, and that the xtra mechanism has been inserted
 */

objref xx, yy, zz, length       // original data, irregularly spaced
objref xint, yint, zint, range  // interpolated data, spaced at regular intervals

proc grindaway() { local ii, nn, kk, xr
	forall {
	  if (ismembrane("xtra")) {
		// get the data for the section
		nn = n3d()
		xx = new Vector(nn)
		yy = new Vector(nn)
		zz = new Vector(nn)
		length = new Vector(nn)

		for ii = 0,nn-1 {
			xx.x[ii] = x3d(ii)
			yy.x[ii] = y3d(ii)
			zz.x[ii] = z3d(ii)
			length.x[ii] = arc3d(ii)
		}

		// to use Vector class's .interpolate() 
		// must first scale the independent variable
		// i.e. normalize length along centroid
		length.div(length.x[nn-1])

		// initialize the destination "independent" vector
		range = new Vector(nseg+2)
		range.indgen(1/nseg)
		range.sub(1/(2*nseg))
		range.x[0]=0
		range.x[nseg+1]=1

		// length contains the normalized distances of the pt3d points 
		// along the centroid of the section.  These are spaced at 
		// irregular intervals.
		// range contains the normalized distances of the nodes along the 
		// centroid of the section.  These are spaced at regular intervals.
		// Ready to interpolate.

		xint = new Vector(nseg+2)
		yint = new Vector(nseg+2)
		zint = new Vector(nseg+2)
		xint.interpolate(range, length, xx)
		yint.interpolate(range, length, yy)
		zint.interpolate(range, length, zz)

		// for each node, assign the xyz values to x_xtra, y_xtra, z_xtra
        // don't bother computing coords of the 0 and 1 ends
        // also avoid writing coords of the 1 end into the last internal node's coords
		for ii = 1, nseg {
			xr = range.x[ii]
			x_xtra(xr) = xint.x[ii]
			y_xtra(xr) = yint.x[ii]
			z_xtra(xr) = zint.x[ii]
		}
	  }
	}
}