comp.lang.idl-pvwave archive: archive » Re: Is there somebody familiar with nurbs or b-Spline?

Home » Public Forums » archive » Re: Is there somebody familiar with nurbs or b-Spline?

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Is there somebody familiar with nurbs or b-Spline? [message #55539 is a reply to message #55537]

Mon, 27 August 2007 08:05

Vince Hradil
Messages: 574
Registered: December 1999

Senior Member

On Aug 27, 4:19 am, airy.ji...@gmail.com wrote:
> In fact,I'm still trying to read the DXF file into IDL.The Spline in
> the DXF is construct with nurbs line.The IDL have a
> method :Spline_P,but it can't reconstruct completely the same
> shape.Who can tell me how to use the nurbs create the Spline.I know
> it's complex and hard to describe,so ,if there are some source code
> can be showed it would be perfect.
> Thanks!

This function worked for me:

First I get all the controlpts for the spline. Then, in my function
ncp=# of control points, the controlpts are (in my case) 2 X ncp.
nsegs is the number of line segments per controlpt that I want to make
my spline into (4L is usually enough for me). The returned value is
the 2 X (nsegs*ncp) line segments needed to dray a polyline.

Hope this helps.

function eval_spline, ncp, controlpts, nsegs

tarray = findgen(nsegs)/(nsegs)
np = (ncp-1)/3

sval = fltarr(2,nsegs*np+1)
for i=0l, np-1 do begin
p0 = controlpts[*,3*i]
p1 = controlpts[*,3*i+1]
p2 = controlpts[*,3*i+2]
p3 = controlpts[*,3*i+3]

sval[*,nsegs*i] = p0
for j=1l, nsegs-1 do begin
t = tarray[j]
vert = p0*(1-t)*(1-t)*(1-t) + p1*3.0*t*(1-t)*(1-t) +
p2*3.0*t*t*(1-t) + p3*t*t*t
sval[*,nsegs*i+j] = vert
endfor
endfor
sval[*,nsegs*np] = controlpts[*,ncp-1]

return, sval
end

Report message to a moderator

[Message index]

		Re: Is there somebody familiar with nurbs or b-Spline? By: airy.jiang on Mon, 27 August 2007 08:46
		Re: Is there somebody familiar with nurbs or b-Spline? By: Vince Hradil on Mon, 27 August 2007 08:05
		Re: Is there somebody familiar with nurbs or b-Spline? By: airy.jiang on Mon, 27 August 2007 21:41

Previous Topic:	Weighted histogram
Next Topic:	Is there somebody familiar with nurbs or b-Spline?

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Wed Oct 08 19:14:03 PDT 2025

Total time taken to generate the page: 0.00427 seconds