Hi,

Guest

NH

Nathan Hellweg

Mon, Oct 14, 2024 9:01 PM

I found a bug that was causing the textures to happen.

I found a bug that was causing the textures to happen.

SP

Sanjeev Prabhakar

Mon, Oct 14, 2024 10:57 PM

This looks interesting

Can you share the reference paper?

On Tue, 15 Oct, 2024, 2:31 am Nathan Hellweg via Discuss, <

discuss@lists.openscad.org> wrote:

I found a bug that was causing the textures to happen.

OpenSCAD mailing list

To unsubscribe send an email to discuss-leave@lists.openscad.org

This looks interesting
Can you share the reference paper?
On Tue, 15 Oct, 2024, 2:31 am Nathan Hellweg via Discuss, <
discuss@lists.openscad.org> wrote:
> I found a bug that was causing the textures to happen.
>
>
> _______________________________________________
> OpenSCAD mailing list
> To unsubscribe send an email to discuss-leave@lists.openscad.org
>

NH

Nathan Hellweg

Tue, Oct 15, 2024 1:13 AM

Of course.

It was at:

http://www.math.tau.ac.il/~niradyn/papers/butterfly.pdf

but the link isn't super reliable, so I've attached a copy.

On Tue, Oct 15, 2024 at 04:27:55AM +0530, Sanjeev Prabhakar wrote:

This looks interesting

Can you share the reference paper?

On Tue, 15 Oct, 2024, 2:31???am Nathan Hellweg via Discuss, <

discuss@lists.openscad.org> wrote:

I found a bug that was causing the textures to happen.

OpenSCAD mailing list

To unsubscribe send an email to discuss-leave@lists.openscad.org

Of course.
It was at:
http://www.math.tau.ac.il/~niradyn/papers/butterfly.pdf
but the link isn't super reliable, so I've attached a copy.
On Tue, Oct 15, 2024 at 04:27:55AM +0530, Sanjeev Prabhakar wrote:
> This looks interesting
> Can you share the reference paper?
>
>
> On Tue, 15 Oct, 2024, 2:31???am Nathan Hellweg via Discuss, <
> discuss@lists.openscad.org> wrote:
>
>
> > I found a bug that was causing the textures to happen.
> >
> >
> > _______________________________________________
> > OpenSCAD mailing list
> > To unsubscribe send an email to discuss-leave@lists.openscad.org
> >

SP

Sanjeev Prabhakar

Tue, Oct 15, 2024 2:09 AM

Thanks Nathan

Let me read and see what can be done with this new knowledge

On Tue, 15 Oct, 2024, 6:43 am Nathan Hellweg, <

nate-openscadforum@pedantic.org> wrote:

Of course.

It was at:

http://www.math.tau.ac.il/~niradyn/papers/butterfly.pdf

but the link isn't super reliable, so I've attached a copy.

On Tue, Oct 15, 2024 at 04:27:55AM +0530, Sanjeev Prabhakar wrote:

This looks interesting

Can you share the reference paper?

On Tue, 15 Oct, 2024, 2:31???am Nathan Hellweg via Discuss, <

discuss@lists.openscad.org> wrote:

I found a bug that was causing the textures to happen.

OpenSCAD mailing list

To unsubscribe send an email to discuss-leave@lists.openscad.org

Thanks Nathan
Let me read and see what can be done with this new knowledge
On Tue, 15 Oct, 2024, 6:43 am Nathan Hellweg, <
nate-openscadforum@pedantic.org> wrote:
> Of course.
>
> It was at:
>
> http://www.math.tau.ac.il/~niradyn/papers/butterfly.pdf
>
> but the link isn't super reliable, so I've attached a copy.
>
> On Tue, Oct 15, 2024 at 04:27:55AM +0530, Sanjeev Prabhakar wrote:
> > This looks interesting
> > Can you share the reference paper?
> >
> >
> > On Tue, 15 Oct, 2024, 2:31???am Nathan Hellweg via Discuss, <
> > discuss@lists.openscad.org> wrote:
> >
> >
> > > I found a bug that was causing the textures to happen.
> > >
> > >
> > > _______________________________________________
> > > OpenSCAD mailing list
> > > To unsubscribe send an email to discuss-leave@lists.openscad.org
> > >
>

JD

John David

Wed, Oct 16, 2024 11:41 AM

Sanjeev & Nathan,

Another potential source for this topic is Gerald Farin's "Curves and

Surfaces for CAGD: a practical guide". When I was looking up the proper

name I found an PDF version online <

https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I

think one of the big additions starting with his 5'th addition was the

introduction of "Blossom" notation (which simplified many of the equations

by a factor of 5 or 10). It has been decades since I took his CAGD class,

and probably have forgotten most of the details, but he has some gems in

there with surface decimation and interpolation.

Hope this helps,

EBo --

On Mon, Oct 14, 2024 at 10:10 PM Sanjeev Prabhakar via Discuss <

discuss@lists.openscad.org> wrote:

Thanks Nathan

Let me read and see what can be done with this new knowledge

On Tue, 15 Oct, 2024, 6:43 am Nathan Hellweg, <

nate-openscadforum@pedantic.org> wrote:

Of course.

It was at:

http://www.math.tau.ac.il/~niradyn/papers/butterfly.pdf

but the link isn't super reliable, so I've attached a copy.

On Tue, Oct 15, 2024 at 04:27:55AM +0530, Sanjeev Prabhakar wrote:

This looks interesting

Can you share the reference paper?

On Tue, 15 Oct, 2024, 2:31???am Nathan Hellweg via Discuss, <

discuss@lists.openscad.org> wrote:

I found a bug that was causing the textures to happen.

OpenSCAD mailing list

To unsubscribe send an email to discuss-leave@lists.openscad.org

OpenSCAD mailing list

To unsubscribe send an email to discuss-leave@lists.openscad.org

Sanjeev & Nathan,
Another potential source for this topic is Gerald Farin's "Curves and
Surfaces for CAGD: a practical guide". When I was looking up the proper
name I found an PDF version online <
https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I
think one of the big additions starting with his 5'th addition was the
introduction of "Blossom" notation (which simplified many of the equations
by a factor of 5 or 10). It has been decades since I took his CAGD class,
and probably have forgotten most of the details, but he has some gems in
there with surface decimation and interpolation.
Hope this helps,
EBo --
On Mon, Oct 14, 2024 at 10:10 PM Sanjeev Prabhakar via Discuss <
discuss@lists.openscad.org> wrote:
> Thanks Nathan
> Let me read and see what can be done with this new knowledge
>
> On Tue, 15 Oct, 2024, 6:43 am Nathan Hellweg, <
> nate-openscadforum@pedantic.org> wrote:
>
>> Of course.
>>
>> It was at:
>>
>> http://www.math.tau.ac.il/~niradyn/papers/butterfly.pdf
>>
>> but the link isn't super reliable, so I've attached a copy.
>>
>> On Tue, Oct 15, 2024 at 04:27:55AM +0530, Sanjeev Prabhakar wrote:
>> > This looks interesting
>> > Can you share the reference paper?
>> >
>> >
>> > On Tue, 15 Oct, 2024, 2:31???am Nathan Hellweg via Discuss, <
>> > discuss@lists.openscad.org> wrote:
>> >
>> >
>> > > I found a bug that was causing the textures to happen.
>> > >
>> > >
>> > > _______________________________________________
>> > > OpenSCAD mailing list
>> > > To unsubscribe send an email to discuss-leave@lists.openscad.org
>> > >
>>
> _______________________________________________
> OpenSCAD mailing list
> To unsubscribe send an email to discuss-leave@lists.openscad.org
>

SP

Sanjeev Prabhakar

Wed, Oct 16, 2024 12:51 PM

Wow

Great and Thanks John for sharing this book

There is a lot to study now for me in next few weekends.

On Wed, 16 Oct, 2024, 5:11 pm John David, ebo.2112@gmail.com wrote:

Sanjeev & Nathan,

Another potential source for this topic is Gerald Farin's "Curves and

Surfaces for CAGD: a practical guide". When I was looking up the proper

name I found an PDF version online <

https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I

think one of the big additions starting with his 5'th addition was the

introduction of "Blossom" notation (which simplified many of the equations

by a factor of 5 or 10). It has been decades since I took his CAGD class,

and probably have forgotten most of the details, but he has some gems in

there with surface decimation and interpolation.

Hope this helps,

EBo --

On Mon, Oct 14, 2024 at 10:10 PM Sanjeev Prabhakar via Discuss <

discuss@lists.openscad.org> wrote:

Thanks Nathan

Let me read and see what can be done with this new knowledge

On Tue, 15 Oct, 2024, 6:43 am Nathan Hellweg, <

nate-openscadforum@pedantic.org> wrote:

Of course.

It was at:

http://www.math.tau.ac.il/~niradyn/papers/butterfly.pdf

but the link isn't super reliable, so I've attached a copy.

On Tue, Oct 15, 2024 at 04:27:55AM +0530, Sanjeev Prabhakar wrote:

This looks interesting

Can you share the reference paper?

On Tue, 15 Oct, 2024, 2:31???am Nathan Hellweg via Discuss, <

discuss@lists.openscad.org> wrote:

I found a bug that was causing the textures to happen.

OpenSCAD mailing list

To unsubscribe send an email to discuss-leave@lists.openscad.org

OpenSCAD mailing list

To unsubscribe send an email to discuss-leave@lists.openscad.org

Wow
Great and Thanks John for sharing this book
There is a lot to study now for me in next few weekends.
On Wed, 16 Oct, 2024, 5:11 pm John David, <ebo.2112@gmail.com> wrote:
> Sanjeev & Nathan,
>
> Another potential source for this topic is Gerald Farin's "Curves and
> Surfaces for CAGD: a practical guide". When I was looking up the proper
> name I found an PDF version online <
> https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I
> think one of the big additions starting with his 5'th addition was the
> introduction of "Blossom" notation (which simplified many of the equations
> by a factor of 5 or 10). It has been decades since I took his CAGD class,
> and probably have forgotten most of the details, but he has some gems in
> there with surface decimation and interpolation.
>
> Hope this helps,
>
> EBo --
>
> On Mon, Oct 14, 2024 at 10:10 PM Sanjeev Prabhakar via Discuss <
> discuss@lists.openscad.org> wrote:
>
>> Thanks Nathan
>> Let me read and see what can be done with this new knowledge
>>
>> On Tue, 15 Oct, 2024, 6:43 am Nathan Hellweg, <
>> nate-openscadforum@pedantic.org> wrote:
>>
>>> Of course.
>>>
>>> It was at:
>>>
>>> http://www.math.tau.ac.il/~niradyn/papers/butterfly.pdf
>>>
>>> but the link isn't super reliable, so I've attached a copy.
>>>
>>> On Tue, Oct 15, 2024 at 04:27:55AM +0530, Sanjeev Prabhakar wrote:
>>> > This looks interesting
>>> > Can you share the reference paper?
>>> >
>>> >
>>> > On Tue, 15 Oct, 2024, 2:31???am Nathan Hellweg via Discuss, <
>>> > discuss@lists.openscad.org> wrote:
>>> >
>>> >
>>> > > I found a bug that was causing the textures to happen.
>>> > >
>>> > >
>>> > > _______________________________________________
>>> > > OpenSCAD mailing list
>>> > > To unsubscribe send an email to discuss-leave@lists.openscad.org
>>> > >
>>>
>> _______________________________________________
>> OpenSCAD mailing list
>> To unsubscribe send an email to discuss-leave@lists.openscad.org
>>
>

NH

Nathan Hellweg

Tue, Oct 22, 2024 2:31 PM

I started reading on this, and ran into some confusion about the norm ellipse

stuff in Chapter 2. I found errata about it at:

https://www.farinhansford.com/books/cagd/errata5.html

Which include:

...

p. 20, Section 2.3 should be skipped because the equation P^TAP = I is incorrect. Also, the ellipse in Figure 2.5 is not accurate. For a derivation of the norm ellipse, see our lecture slides for Practical Linear Algebra. Start at slide 35 - principal components analysis in the file http://www.farinhansford.com/books/pla/material/chap16.pdf (Karen Daniels, Bob Marceau, Franck Kamayou, and Adam Russell) [11/14].

...

But, the referenced pdf doesn't seem to mention norm ellipses at all. (The only

referenced ellipse is an "action ellipse".) Do you remember anything about

that? I've also tried searching for "norm ellipse" on line without finding

clarification. FWIW, it also looks like "norm ellipse" doesn't show up

anywhere else in the book. So maybe I should just leave it be and read on.

On Wed, Oct 16, 2024 at 07:41:41AM -0400, John David wrote:

Sanjeev & Nathan,

Another potential source for this topic is Gerald Farin's "Curves and

Surfaces for CAGD: a practical guide". When I was looking up the proper

name I found an PDF version online <

https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I

think one of the big additions starting with his 5'th addition was the

introduction of "Blossom" notation (which simplified many of the equations

by a factor of 5 or 10). It has been decades since I took his CAGD class,

and probably have forgotten most of the details, but he has some gems in

there with surface decimation and interpolation.

Hope this helps,

EBo --

--

Nathan

I started reading on this, and ran into some confusion about the norm ellipse
stuff in Chapter 2. I found errata about it at:
https://www.farinhansford.com/books/cagd/errata5.html
Which include:
...
p. 20, Section 2.3 should be skipped because the equation P^TAP = I is incorrect. Also, the ellipse in Figure 2.5 is not accurate. For a derivation of the norm ellipse, see our lecture slides for Practical Linear Algebra. Start at slide 35 - principal components analysis in the file http://www.farinhansford.com/books/pla/material/chap16.pdf (Karen Daniels, Bob Marceau, Franck Kamayou, and Adam Russell) [11/14].
...
But, the referenced pdf doesn't seem to mention norm ellipses at all. (The only
referenced ellipse is an "action ellipse".) Do you remember anything about
that? I've also tried searching for "norm ellipse" on line without finding
clarification. FWIW, it also looks like "norm ellipse" doesn't show up
anywhere else in the book. So maybe I should just leave it be and read on.
On Wed, Oct 16, 2024 at 07:41:41AM -0400, John David wrote:
> Sanjeev & Nathan,
>
>
> Another potential source for this topic is Gerald Farin's "Curves and
> Surfaces for CAGD: a practical guide". When I was looking up the proper
> name I found an PDF version online <
> https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I
> think one of the big additions starting with his 5'th addition was the
> introduction of "Blossom" notation (which simplified many of the equations
> by a factor of 5 or 10). It has been decades since I took his CAGD class,
> and probably have forgotten most of the details, but he has some gems in
> there with surface decimation and interpolation.
>
>
> Hope this helps,
>
>
> EBo --
>
--
Nathan

JD

John David

Tue, Oct 22, 2024 10:10 PM

Not off the top of my head (it has been 20+ years since I first cracked the

book), but give me a couple of days to check.

I started writing a note about the two different CAGD series, the one with

his wife Dianne Hansford "Essentials of CAGD", and Gerald Farin's "Curves

and Surfaces: a practical guide". But I see that the erata is specifically

on a website for the 5'th edition. That said, I will give it a quick try:

I think his reference to the "norm ellipse" is to the references he gives

(including [90] F. Bookstein. Fitting conic sections to scattered data.

CGIP, 9:56-71,1979). I see the term "norm ellipse" used in figure 2.5 (pg

22) and elsewhere on pages 20, and 21. One other term that might be helpful

is osculating circles and planes (pg. 179-189) and see if that helps.

I think this is one that you might have to write Dianne about (the erata

site gives her email address).

Hope this helps.

EBo --

On Tue, Oct 22, 2024 at 10:31 AM Nathan Hellweg <

nate-openscadforum@pedantic.org> wrote:

I started reading on this, and ran into some confusion about the norm

ellipse

stuff in Chapter 2. I found errata about it at:

https://www.farinhansford.com/books/cagd/errata5.html

Which include:

...

p. 20, Section 2.3 should be skipped because the equation P^TAP = I is

incorrect. Also, the ellipse in Figure 2.5 is not accurate. For a

derivation of the norm ellipse, see our lecture slides for Practical Linear

Algebra. Start at slide 35 - principal components analysis in the file

http://www.farinhansford.com/books/pla/material/chap16.pdf (Karen

Daniels, Bob Marceau, Franck Kamayou, and Adam Russell) [11/14].

...

But, the referenced pdf doesn't seem to mention norm ellipses at all.

(The only

referenced ellipse is an "action ellipse".) Do you remember anything about

that? I've also tried searching for "norm ellipse" on line without finding

clarification. FWIW, it also looks like "norm ellipse" doesn't show up

anywhere else in the book. So maybe I should just leave it be and read on.

On Wed, Oct 16, 2024 at 07:41:41AM -0400, John David wrote:

Sanjeev & Nathan,

Another potential source for this topic is Gerald Farin's "Curves and

Surfaces for CAGD: a practical guide". When I was looking up the proper

name I found an PDF version online <

https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I

think one of the big additions starting with his 5'th addition was the

introduction of "Blossom" notation (which simplified many of the

equations

by a factor of 5 or 10). It has been decades since I took his CAGD

class,

and probably have forgotten most of the details, but he has some gems in

there with surface decimation and interpolation.

Hope this helps,

EBo --

--

Nathan

Not off the top of my head (it has been 20+ years since I first cracked the
book), but give me a couple of days to check.
I started writing a note about the two different CAGD series, the one with
his wife Dianne Hansford "Essentials of CAGD", and Gerald Farin's "Curves
and Surfaces: a practical guide". But I see that the erata is specifically
on a website for the 5'th edition. That said, I will give it a quick try:
I think his reference to the "norm ellipse" is to the references he gives
(including [90] F. Bookstein. Fitting conic sections to scattered data.
CGIP, 9:56-71,1979). I see the term "norm ellipse" used in figure 2.5 (pg
22) and elsewhere on pages 20, and 21. One other term that might be helpful
is osculating circles and planes (pg. 179-189) and see if that helps.
I think this is one that you might have to write Dianne about (the erata
site gives her email address).
Hope this helps.
EBo --
On Tue, Oct 22, 2024 at 10:31 AM Nathan Hellweg <
nate-openscadforum@pedantic.org> wrote:
> I started reading on this, and ran into some confusion about the norm
> ellipse
> stuff in Chapter 2. I found errata about it at:
>
> https://www.farinhansford.com/books/cagd/errata5.html
>
> Which include:
>
> ...
> p. 20, Section 2.3 should be skipped because the equation P^TAP = I is
> incorrect. Also, the ellipse in Figure 2.5 is not accurate. For a
> derivation of the norm ellipse, see our lecture slides for Practical Linear
> Algebra. Start at slide 35 - principal components analysis in the file
> http://www.farinhansford.com/books/pla/material/chap16.pdf (Karen
> Daniels, Bob Marceau, Franck Kamayou, and Adam Russell) [11/14].
> ...
>
> But, the referenced pdf doesn't seem to mention norm ellipses at all.
> (The only
> referenced ellipse is an "action ellipse".) Do you remember anything about
> that? I've also tried searching for "norm ellipse" on line without finding
> clarification. FWIW, it also looks like "norm ellipse" doesn't show up
> anywhere else in the book. So maybe I should just leave it be and read on.
>
> On Wed, Oct 16, 2024 at 07:41:41AM -0400, John David wrote:
> > Sanjeev & Nathan,
> >
> >
> > Another potential source for this topic is Gerald Farin's "Curves and
> > Surfaces for CAGD: a practical guide". When I was looking up the proper
> > name I found an PDF version online <
> > https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I
> > think one of the big additions starting with his 5'th addition was the
> > introduction of "Blossom" notation (which simplified many of the
> equations
> > by a factor of 5 or 10). It has been decades since I took his CAGD
> class,
> > and probably have forgotten most of the details, but he has some gems in
> > there with surface decimation and interpolation.
> >
> >
> > Hope this helps,
> >
> >
> > EBo --
> >
>
> --
> Nathan
>

NH

Nathan Hellweg

Wed, Oct 23, 2024 12:35 PM

Thank you. It just seemed like something that might have come up for someone

who went through the book in the past. I did also notice a typesetting error

that isn't mentioned in the errata list. So I guess I can write to her.

On Tue, Oct 22, 2024 at 06:10:24PM -0400, John David wrote:

Not off the top of my head (it has been 20+ years since I first cracked the

book), but give me a couple of days to check.

I started writing a note about the two different CAGD series, the one with

his wife Dianne Hansford "Essentials of CAGD", and Gerald Farin's "Curves

and Surfaces: a practical guide". But I see that the erata is specifically

on a website for the 5'th edition. That said, I will give it a quick try:

I think his reference to the "norm ellipse" is to the references he gives

(including [90] F. Bookstein. Fitting conic sections to scattered data.

CGIP, 9:56-71,1979). I see the term "norm ellipse" used in figure 2.5 (pg

22) and elsewhere on pages 20, and 21. One other term that might be helpful

is osculating circles and planes (pg. 179-189) and see if that helps.

I think this is one that you might have to write Dianne about (the erata

site gives her email address).

Hope this helps.

EBo --

On Tue, Oct 22, 2024 at 10:31???AM Nathan Hellweg <

nate-openscadforum@pedantic.org> wrote:

I started reading on this, and ran into some confusion about the norm

ellipse

stuff in Chapter 2. I found errata about it at:https://www.farinhansford.com/books/cagd/errata5.html

Which include:

...

p. 20, Section 2.3 should be skipped because the equation P^TAP = I is

incorrect. Also, the ellipse in Figure 2.5 is not accurate. For a

derivation of the norm ellipse, see our lecture slides for Practical Linear

Algebra. Start at slide 35 - principal components analysis in the file

http://www.farinhansford.com/books/pla/material/chap16.pdf (Karen

Daniels, Bob Marceau, Franck Kamayou, and Adam Russell) [11/14].

...But, the referenced pdf doesn't seem to mention norm ellipses at all.

(The only

referenced ellipse is an "action ellipse".) Do you remember anything about

that? I've also tried searching for "norm ellipse" on line without finding

clarification. FWIW, it also looks like "norm ellipse" doesn't show up

anywhere else in the book. So maybe I should just leave it be and read on.On Wed, Oct 16, 2024 at 07:41:41AM -0400, John David wrote:

Sanjeev & Nathan,

Surfaces for CAGD: a practical guide". When I was looking up the proper

name I found an PDF version online <

https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I

think one of the big additions starting with his 5'th addition was the

introduction of "Blossom" notation (which simplified many of the

equations

by a factor of 5 or 10). It has been decades since I took his CAGD

class,

and probably have forgotten most of the details, but he has some gems in

there with surface decimation and interpolation.Hope this helps,

EBo --

--

Nathan

Thank you. It just seemed like something that might have come up for someone
who went through the book in the past. I did also notice a typesetting error
that isn't mentioned in the errata list. So I guess I can write to her.
On Tue, Oct 22, 2024 at 06:10:24PM -0400, John David wrote:
> Not off the top of my head (it has been 20+ years since I first cracked the
> book), but give me a couple of days to check.
>
>
> I started writing a note about the two different CAGD series, the one with
> his wife Dianne Hansford "Essentials of CAGD", and Gerald Farin's "Curves
> and Surfaces: a practical guide". But I see that the erata is specifically
> on a website for the 5'th edition. That said, I will give it a quick try:
>
>
> I think his reference to the "norm ellipse" is to the references he gives
> (including [90] F. Bookstein. Fitting conic sections to scattered data.
> CGIP, 9:56-71,1979). I see the term "norm ellipse" used in figure 2.5 (pg
> 22) and elsewhere on pages 20, and 21. One other term that might be helpful
> is osculating circles and planes (pg. 179-189) and see if that helps.
>
>
> I think this is one that you might have to write Dianne about (the erata
> site gives her email address).
>
>
> Hope this helps.
>
>
> EBo --
>
>
> On Tue, Oct 22, 2024 at 10:31???AM Nathan Hellweg <
> nate-openscadforum@pedantic.org> wrote:
>
>
> > I started reading on this, and ran into some confusion about the norm
> > ellipse
> > stuff in Chapter 2. I found errata about it at:
> >
> > https://www.farinhansford.com/books/cagd/errata5.html
> >
> > Which include:
> >
> > ...
> > p. 20, Section 2.3 should be skipped because the equation P^TAP = I is
> > incorrect. Also, the ellipse in Figure 2.5 is not accurate. For a
> > derivation of the norm ellipse, see our lecture slides for Practical Linear
> > Algebra. Start at slide 35 - principal components analysis in the file
> > http://www.farinhansford.com/books/pla/material/chap16.pdf (Karen
> > Daniels, Bob Marceau, Franck Kamayou, and Adam Russell) [11/14].
> > ...
> >
> > But, the referenced pdf doesn't seem to mention norm ellipses at all.
> > (The only
> > referenced ellipse is an "action ellipse".) Do you remember anything about
> > that? I've also tried searching for "norm ellipse" on line without finding
> > clarification. FWIW, it also looks like "norm ellipse" doesn't show up
> > anywhere else in the book. So maybe I should just leave it be and read on.
> >
> > On Wed, Oct 16, 2024 at 07:41:41AM -0400, John David wrote:
> > > Sanjeev & Nathan,
> > >
> > >
> > > Another potential source for this topic is Gerald Farin's "Curves and
> > > Surfaces for CAGD: a practical guide". When I was looking up the proper
> > > name I found an PDF version online <
> > > https://www.cin.ufpe.br/~mdlm/files/Farin-5a_edicao.pdf> As a note, I
> > > think one of the big additions starting with his 5'th addition was the
> > > introduction of "Blossom" notation (which simplified many of the
> > equations
> > > by a factor of 5 or 10). It has been decades since I took his CAGD
> > class,
> > > and probably have forgotten most of the details, but he has some gems in
> > > there with surface decimation and interpolation.
> > >
> > >
> > > Hope this helps,
> > >
> > >
> > > EBo --
> > >
> >
> > --
> > Nathan
> >

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