Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!ucsd!sdcsvax!ucsdhub!hp-sdd!hplabs!hpda!hpcuhb!hp-ses!hpcc01!hpwrce!ted
From: ted@hpwrce.HP.COM ( Ted Johnson)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Graf3D and Color???
Message-ID: <7430014@hpwrce.HP.COM>
Date: 11 Apr 89 01:53:13 GMT
References: <6207@sdcsvax.UCSD.Edu>
Organization: Ye Olde Salt Mines
Lines: 34

(my mailer choked on this, so I'm posting it here)


>To: leeke@mips.csc.ti.com, ted@hpwrce.HP.COM
>Subject: Re: Graf3D and Color???
>
>>P.S. Speaking of B-splines, did 'ja notice all the bugs in the Bezier
>>     spline code in the Jan '89 MacTutor?  I wrote 'em a letter which
>>     showed the *correct* blending functions, but they never bothered
>>     to publish it.  :-(
>
>Ted:
>
>Could you send me the corrections?
>
>Thanks,

Here they are:

w1(t) = (1-t)**3     (not (t-1)**3)

w2(t) = 3t(1-t)**2   (not (3t**3(t-1))

w3(t) = 3t**2(1-t)    (not (3t(1-t)**2)

w4(t) = t**3   (the article got this one correct)


Strangely enough, the author got the first blending function
correct in his code.  The second one would also be correct,
but he got the 1 and the t backwards.


-Ted