plib-users

Re: [Plib-users] Problem with rotations results

[Steve B. <sjb...@ai...>]

Ben Woodhead wrote:

> Wow, I had no idea the results returning from a matrix were that like that.. I 
> understood what you meant, when you said h <> h, and so on. But I didn't 
> realise just how off they would actually be.

Yes - well, it's a mathematical fact.  There are an infinite number of ways
to represent an arbitary rotation matrix in terms of Euler angles - and the
code has no way to know which one you wanted - so it just picks one.

It's hard to know what else we could do.

> Anyway back to the point, I was 
> wrong about the 0 and 180, its at 90 degrees that cause the problem. Here is 
> the header, pitch and role from the 3 different rotations. Take a close look 
> at the pitch.

(BTW: The word is "Roll" - not "Role" and "Heading" - not "Header")

> Pitch
> Header: -0.000000, Pitch: 88.002075, Role: -0.000000
> Header: -0.000000, Pitch: 89.004166, Role: -0.000000
> Header: 0.000000, Pitch: 90.000000, Role: 90.000000

Eh?  Are you sure the heading was zero?  I'd expect it to
be -90 or something.

But anyway - this *is* classic 'Gymbal Lock'.

As Norman suggested, you can visualise it in these
terms:

     "A hunter walks South one mile from his tent, then
      he is chased due East for one mile by a ferocious Bear.
      Having escaped, he walks North for one mile and finds
      himself back at his tent.  What colour was the Bear?"

     (White!)

> As you can see in pitch when it hits 90 on pitch, role also goes to 90. The 
> one thing that I just noticed is that non of the other rotations get to 
> exactly 90.0. 

It's not so much that Roll or Pitch is special, it actually comes
about that way because of the order of rotational operations.

The bottom line is that Mat-to-Coord is working OK - it's just
that you have to understand it's limitations.

----------------------------- Steve Baker -------------------------------
Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
URLs : http://www.sjbaker.org
        http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
        http://prettypoly.sf.net http://freeglut.sf.net
        http://toobular.sf.net   http://lodestone.sf.net

Re: [Plib-users] The examples

[Steve B. <sjb...@ai...>]

Sebastian Ude wrote:

> Aaargh - Steve, the 'config.guess', 'config.sub', 'install-sh', 'missing'
> and 'mkinstalldirs' scripts (automatically copied into the directory when
> doing "autoconf") are missing in the plib_examples, p-guide and exposer
> tarballs.


So, I use 'make dist' to make the distribution tarball - and it *used* to
work.  Something must have happened to 'Makefile.am's "extra-dist" entry.

Ah - yes - checking the CVS records, I see that *SOMEONE* has removed the
entry requiring those files.

That happened between version 1.5 and 1.6 of examples/Makefile.am ...and
that entry was committed by....

     Revision 1.6, Wed May 8 21:24:24 2002 UTC (4 months ago) by ude

Hmmmm - someone by the name of "ude" ??

----------------------------- Steve Baker -------------------------------
Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
URLs : http://www.sjbaker.org
        http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
        http://prettypoly.sf.net http://freeglut.sf.net
        http://toobular.sf.net   http://lodestone.sf.net

[Plib-users] RE: Problem with rotations

[McEvoy, N. <nic...@ds...>]

Ben Woodhead wrote:
>As you can see in pitch when it hits 90 on pitch, role also
>goes to 90. The one thing that I just noticed is that non of
>the other rotations get to exactly 90.0.
>Any ideas, thanks for all your help steve.

You really gotta take Steve's advice on this ... it is gymbal lock ... read
and understand those links he mentioned. :-)

I had the same trouble when I started with matrices ... it drove me crazy
(and still does) ... my model flipped all over the place when I hit 90 pitch
... I even tried Quats (eg. sgHPRToQuat) ... which (I thought) should avoid
the problem ... but unfortunately I couldn't get them to work either ... I'm
still not sure why !?

I now use ODE (a physics engine) and PLIB for the graphics.  ODE does all
the rotation work for me and avoids the 'gymbal lock' problem ... but before
I found ODE I did fix the problem you are having by doing the following
(notice I never let the pitch hit exactly 90) ...

// If the eyepoint it pitched by 90 degrees - then roll and heading do the
same
// thing and the whole thing goes crazy ... so ensure we never point exactly
90.
if (mPosition.hpr[1] == 90.0f)
	mPosition.hpr[1] -= 0.2f;
if (mPosition.hpr[1] == -90.0f)
	mPosition.hpr[1] += 0.2f;

// Update player hpr
sgMat4 POS, ROT;
sgMakeCoordMat4(POS, &mPosition);
sgMakeRotMat4(ROT, mDirChange);
sgPreMultMat4(POS, ROT);
sgSetCoord(&mPosition, POS);

I hope that helps.

Good luck !

Nick
http://members.ozemail.com.au/~ndmcevoy/

[Plib-users] (no subject)

[Antonio L. <sup...@ho...>]

Hello everybody, I'm programming a stunt racing game but I have graphics 
problems - I'm using plib1.6.0 on win$ - I tried tuxkart and no such problem 
occour so it's my mistake for sure.
Please look at members.xoom.virgilio.it/Devas fot the files snapshot1.jpg , 
snapshot2.jpg and snapshot3.jpg.
In short, polygons are disappearing and reappearing and I don't understand 
if I have to tune some params (I checked that near and far plane are 0.01 
and 1000 so this clipping should not be related to it).
What I would liked to achieve in the shots was to have my car inside a big 
box, modeled in my favourite 3d proggy (blender) and exported to ac format.
The lower face of the box (the one where the car sits on) has more triangles 
as I have modeled a terrain.
The normals of the faces are toward the inside of the box.
I have also placed a model of a "ramp", the orange polygons.
As you can see triangles disappear, the ramp become segmented as soon as I 
move a bit the point of view (see difference between snapshot3 and 
snapshot2)...
if I make the box bigger, it completely disappear (even the floor, which is 
near the camera, is not visible) any suggestion would be greatly 
appreciated!!



_________________________________________________________________
Chat with friends online, try MSN Messenger: http://messenger.msn.com

Re: [Plib-users] The examples

[<ha...@sl...>]

About the OpenGL Context, are you using Red Hat 7.2?  If so, I believe 
they updated their Mesa package to fix this problem.

--
Brian


On Tue, 10 Sep 2002, Ramy Sadek wrote:

>Hi all. I hope I'm not stating a known or obvious problem.
>
> The examples don't work for me. If I try to get 1.6.1, configure 
>complains about install-sh missing. If I run the compile by hand (which 
>works) for, say, viewer, I get an error complaining that ssgInit is 
>called without a valid OpenGL context. This seems bizarre since I 
>haven't touched the code itself.
>
>Anyone have similar problems?
>
>-Ramy
>
>
>
>-------------------------------------------------------
>In remembrance
>www.osdn.com/911/
>_______________________________________________
>plib-users mailing list
>pli...@li...
>https://lists.sourceforge.net/lists/listinfo/plib-users
>

-- 
Brian Hayward

Re: [Plib-users] The examples

[Sebastian U. <ud...@ha...>]

On Tue, 10 Sep 2002, sa...@ic... (Ramy Sadek) wrote:
> Date: Tue, 10 Sep 2002 14:35:16 -0700
> To: pli...@li...
> From: sa...@ic... (Ramy Sadek)
> Reply-To: pli...@li...
> Subject: [Plib-users] The examples
>
> Hi all. I hope I'm not stating a known or obvious problem.
>
>  The examples don't work for me. If I try to get 1.6.1, configure 
> complains about install-sh missing. If I run the compile by hand (which 
> works) for, say, viewer, I get an error complaining that ssgInit is 
> called without a valid OpenGL context. This seems bizarre since I 
> haven't touched the code itself.

Aaargh - Steve, the 'config.guess', 'config.sub', 'install-sh', 'missing'
and 'mkinstalldirs' scripts (automatically copied into the directory when
doing "autoconf") are missing in the plib_examples, p-guide and exposer
tarballs.

Argh !


- Sebastian

[Plib-users] The examples

[Ramy S. <sa...@ic...>]

Hi all. I hope I'm not stating a known or obvious problem.

 The examples don't work for me. If I try to get 1.6.1, configure 
complains about install-sh missing. If I run the compile by hand (which 
works) for, say, viewer, I get an error complaining that ssgInit is 
called without a valid OpenGL context. This seems bizarre since I 
haven't touched the code itself.

Anyone have similar problems?

-Ramy

Re: [Plib-users] Problem with rotations

[Norman V. <nh...@ca...>]

Ben Woodhead writes:


> Ok, sorry my fault, it really was converting it back and forth between
euler
> and matrix. If I keep the matrix the hole time you just see a quick jump
to a
> different axe and then back. But this still does not explain why only
pitch
> does this.
>
> It seems to be only when pitch hits either 0 or 180 (and no others do
this).
> It will rotate with its feet around the x axes, but when x hits 0 or 180,
it
> roles so that its feet are on the y axes rotated 90 degrees. If that makes
> any sence.

Ben

Another way to think about this is
What direction(s) can you walk in if you are
EXACTLY at one of the Poles ?

< not exacly the same problem but very close >

Norman

Re: [Plib-users] Problem with rotations results

[Ben W. <be...@ec...>]

Wow, I had no idea the results returning from a matrix were that like tha=
t.. I=20
understood what you meant, when you said h <> h, and so on. But I didn't=20
realise just how off they would actually be.. Anyway back to the point, I=
 was=20
wrong about the 0 and 180, its at 90 degrees that cause the problem. Here=
 is=20
the header, pitch and role from the 3 different rotations. Take a close l=
ook=20
at the pitch.

Header
Header: 88.999992, Pitch: 0.000000, Role: -0.000000
Header: 89.999992, Pitch: 0.000000, Role: -0.000000
Header: 90.999992, Pitch: 0.000000, Role: -0.000000

Pitch
Header: -0.000000, Pitch: 88.002075, Role: -0.000000
Header: -0.000000, Pitch: 89.004166, Role: -0.000000
Header: 0.000000, Pitch: 90.000000, Role: 90.000000

Role
Header: -0.000000, Pitch: 0.000000, Role: 88.999992
Header: -0.000000, Pitch: 0.000000, Role: 89.999992
Header: -0.000000, Pitch: 0.000000, Role: 90.999992

As you can see in pitch when it hits 90 on pitch, role also goes to 90. T=
he=20
one thing that I just noticed is that non of the other rotations get to=20
exactly 90.0.=20

Any ideas, thanks for all your help steve.
Ben

Re: [Plib-users] Problem with rotations

[Ben W. <be...@ec...>]

Ok, sorry my fault, it really was converting it back and forth between eu=
ler=20
and matrix. If I keep the matrix the hole time you just see a quick jump =
to a=20
different axe and then back. But this still does not explain why only pit=
ch=20
does this.=20

It seems to be only when pitch hits either 0 or 180 (and no others do thi=
s).=20
It will rotate with its feet around the x axes, but when x hits 0 or 180,=
 it=20
roles so that its feet are on the y axes rotated 90 degrees. If that make=
s=20
any sence.=20

Thanks for your help, has anybody actually tried the code.

Ben

Re: [Plib-users] Problem with rotations

[Ben W. <za...@ec...>]

Ok, I see what you are talking about and it makes sence. But why would this
only cause a problem with pitch. I know that is questionable to return back
from a matrix, so I tried it just using the matrix and not returning it back
and got the same results..

Ben
----- Original Message -----
From: "Steve Baker" <sjb...@ai...>
To: <pli...@li...>
Sent: Tuesday, September 10, 2002 1:47 AM
Subject: Re: [Plib-users] Problem with rotations


>
>
> Ben Woodhead wrote:
>
> > Ya, I don't have a problem with that.. It seems to be sgMakeRotMat(mat,
> > h,p,r) where pitch is set to something other then 0. Then I converted it
> > back to sgCoord and used transform...
>
> Could your confusion be this:
>
>     * You take three angles (H,P,R) and convert them into a matrix M
>       (using sgMakeRotMat...or whatever).
>
>     * Then you convert M *BACK* into an sgCoord and extract (H',P',R').
>
> Do you expect (or rely upon) H' == H,  P' == P and R' == R ???
>
> If so, then that's not right.  There are an infinite number of values
> for H,P,R that all generate the exact same rotation matrix.  Hence, when
> you convert a matrix *BACK* into three Euler angles, you don't get the
> same three angles back...although the three angles you get *DO* perform
> the same effective rotation as the three you put in.
>
> Hence, it's possible to say things like:
>
>      H =   0
>      P = 180
>      R =   0
>
> ...then convert to a matrix...convert back again and get back:
>
>      H' = 180
>      P' =   0
>      R' = 180
>
> ...totally different numbers - but having the same exact same effect.
>
> If that is your problem, then it's not something that we can fix - it's
> just the way math works.
>
> ----------------------------- Steve Baker -------------------------------
> Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
> URLs : http://www.sjbaker.org
>         http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
>         http://prettypoly.sf.net http://freeglut.sf.net
>         http://toobular.sf.net   http://lodestone.sf.net
>
>
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by: OSDN - Tired of that same old
> cell phone?  Get a new here for FREE!
> https://www.inphonic.com/r.asp?r=sourceforge1&refcode1=vs3390
> _______________________________________________
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> pli...@li...
> https://lists.sourceforge.net/lists/listinfo/plib-users
>

Re: [Plib-users] Problem with rotations

[Ben W. <za...@ec...>]

That is a good question, and I don't know the answer. But why would it work
for header and role.

h=1
p=0
r=0
this works fine and rotates around. same with
h=0
p=0
r=1
it also works fine. Its just
h=0
p=1
r=0
That causing the problem. And why would it jump to another axe and the come
back.
I did also try this with just a matrix, were I created the rotation matrix
with sgMakeRot4, then muliply it by the location and running the transform
without converting it back to euler, but I got the same result.
The thing I find weird is that its only when it hits one axe that it jumps
to anyother one.
Anyway I don't know, I can't find the problem, and I have a test problem
that does it, but I just don't understand why its doing it, so I can't
really explain.
Ben


----- Original Message -----
From: "Steve Baker" <sjb...@ai...>
To: <pli...@li...>
Sent: Tuesday, September 10, 2002 1:47 AM
Subject: Re: [Plib-users] Problem with rotations


>
>
> Ben Woodhead wrote:
>
> > Ya, I don't have a problem with that.. It seems to be sgMakeRotMat(mat,
> > h,p,r) where pitch is set to something other then 0. Then I converted it
> > back to sgCoord and used transform...
>
> Could your confusion be this:
>
>     * You take three angles (H,P,R) and convert them into a matrix M
>       (using sgMakeRotMat...or whatever).
>
>     * Then you convert M *BACK* into an sgCoord and extract (H',P',R').
>
> Do you expect (or rely upon) H' == H,  P' == P and R' == R ???
>
> If so, then that's not right.  There are an infinite number of values
> for H,P,R that all generate the exact same rotation matrix.  Hence, when
> you convert a matrix *BACK* into three Euler angles, you don't get the
> same three angles back...although the three angles you get *DO* perform
> the same effective rotation as the three you put in.
>
> Hence, it's possible to say things like:
>
>      H =   0
>      P = 180
>      R =   0
>
> ...then convert to a matrix...convert back again and get back:
>
>      H' = 180
>      P' =   0
>      R' = 180
>
> ...totally different numbers - but having the same exact same effect.
>
> If that is your problem, then it's not something that we can fix - it's
> just the way math works.
>
> ----------------------------- Steve Baker -------------------------------
> Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
> URLs : http://www.sjbaker.org
>         http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
>         http://prettypoly.sf.net http://freeglut.sf.net
>         http://toobular.sf.net   http://lodestone.sf.net
>
>
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by: OSDN - Tired of that same old
> cell phone?  Get a new here for FREE!
> https://www.inphonic.com/r.asp?r=sourceforge1&refcode1=vs3390
> _______________________________________________
> plib-users mailing list
> pli...@li...
> https://lists.sourceforge.net/lists/listinfo/plib-users
>

Re: [Plib-users] Problem with rotations

[Steve B. <sjb...@ai...>]

Ben Woodhead wrote:

> Ya, I don't have a problem with that.. It seems to be sgMakeRotMat(mat,
> h,p,r) where pitch is set to something other then 0. Then I converted it
> back to sgCoord and used transform...

Could your confusion be this:

    * You take three angles (H,P,R) and convert them into a matrix M
      (using sgMakeRotMat...or whatever).

    * Then you convert M *BACK* into an sgCoord and extract (H',P',R').

Do you expect (or rely upon) H' == H,  P' == P and R' == R ???

If so, then that's not right.  There are an infinite number of values
for H,P,R that all generate the exact same rotation matrix.  Hence, when
you convert a matrix *BACK* into three Euler angles, you don't get the
same three angles back...although the three angles you get *DO* perform
the same effective rotation as the three you put in.

Hence, it's possible to say things like:

     H =   0
     P = 180
     R =   0

...then convert to a matrix...convert back again and get back:

     H' = 180
     P' =   0
     R' = 180

...totally different numbers - but having the same exact same effect.

If that is your problem, then it's not something that we can fix - it's
just the way math works.

----------------------------- Steve Baker -------------------------------
Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
URLs : http://www.sjbaker.org
        http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
        http://prettypoly.sf.net http://freeglut.sf.net
        http://toobular.sf.net   http://lodestone.sf.net

Re: [Plib-users] Problem with rotations

[Ben W. <za...@ec...>]

Sorry Steve,  its not role I was talking about its pitch (rotating around
the x axes).

Ben

----- Original Message -----
From: "Steve Baker" <sjb...@ai...>
To: <pli...@li...>
Sent: Monday, September 09, 2002 11:51 PM
Subject: Re: [Plib-users] Problem with rotations


> Ben Woodhead wrote:
> > I did read these articles but I will read them again. But I did use a
matrix
> > stack from the rotations and I am only rotating around 1 axe. If I
change
> > the code to just rotate around x it works, and if I change it to rotate
> > around just z there is no problem, but just y causes some really weird
> > results. Did you have a look at the code..
>
> Sorry - no - I've been kinda busy.  I've seen *thousands* of cases of
> objects rotating nicely around the Y axis - so I'm not inclined to suspect
> a bug in PLIB...but anything's possible.
>
> Just to be *sure*, I went into examples/src/ssg/tux/tux_example.cxx - and
> changed the line:
>
>    sgSetCoord ( & tuxpos, 0.0f,  0.0f, 0.0f, frameno, 0.0f, 0.0f ) ;
>
> ...and switched 'frameno' from Heading (Rotation about Z) to Roll
(Rotation about Y):
>
>    sgSetCoord ( & tuxpos, 0.0f,  0.0f, 0.0f, 0.0f, 0.0f, frameno ) ;
>
> ...and tux leans to the right, gradually disappears under the pedestal and
> reappears on the left...exactly as I'd expect.
>
> ----------------------------- Steve Baker -------------------------------
> Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
> URLs : http://www.sjbaker.org
>         http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
>         http://prettypoly.sf.net http://freeglut.sf.net
>         http://toobular.sf.net   http://lodestone.sf.net
>
>
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by: OSDN - Tired of that same old
> cell phone?  Get a new here for FREE!
> https://www.inphonic.com/r.asp?r=sourceforge1&refcode1=vs3390
> _______________________________________________
> plib-users mailing list
> pli...@li...
> https://lists.sourceforge.net/lists/listinfo/plib-users
>

Re: [Plib-users] Problem with rotations

[Ben W. <za...@ec...>]

Hello Steve..

Ya, I don't have a problem with that.. It seems to be sgMakeRotMat(mat,
h,p,r) where pitch is set to something other then 0. Then I converted it
back to sgCoord and used transform, although in my code, I also tried just
using the matrix and it did the same thing. Try coping the file that I sent
over tux_example.cxx and see that happens. If you go back to the code in the
update_motion function and user the header or the role things work fine, but
pitch causes problems. I will keep looking for the problem, but I can't find
it, when I seperated into tux_example (so its not something in my
applicaton) and it only happens with pitch (header and role are fine) then I
don't know what else it could be.

Ben

----- Original Message -----
From: "Steve Baker" <sjb...@ai...>
To: <pli...@li...>
Sent: Monday, September 09, 2002 11:51 PM
Subject: Re: [Plib-users] Problem with rotations


> Ben Woodhead wrote:
> > I did read these articles but I will read them again. But I did use a
matrix
> > stack from the rotations and I am only rotating around 1 axe. If I
change
> > the code to just rotate around x it works, and if I change it to rotate
> > around just z there is no problem, but just y causes some really weird
> > results. Did you have a look at the code..
>
> Sorry - no - I've been kinda busy.  I've seen *thousands* of cases of
> objects rotating nicely around the Y axis - so I'm not inclined to suspect
> a bug in PLIB...but anything's possible.
>
> Just to be *sure*, I went into examples/src/ssg/tux/tux_example.cxx - and
> changed the line:
>
>    sgSetCoord ( & tuxpos, 0.0f,  0.0f, 0.0f, frameno, 0.0f, 0.0f ) ;
>
> ...and switched 'frameno' from Heading (Rotation about Z) to Roll
(Rotation about Y):
>
>    sgSetCoord ( & tuxpos, 0.0f,  0.0f, 0.0f, 0.0f, 0.0f, frameno ) ;
>
> ...and tux leans to the right, gradually disappears under the pedestal and
> reappears on the left...exactly as I'd expect.
>
> ----------------------------- Steve Baker -------------------------------
> Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
> URLs : http://www.sjbaker.org
>         http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
>         http://prettypoly.sf.net http://freeglut.sf.net
>         http://toobular.sf.net   http://lodestone.sf.net
>
>
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by: OSDN - Tired of that same old
> cell phone?  Get a new here for FREE!
> https://www.inphonic.com/r.asp?r=sourceforge1&refcode1=vs3390
> _______________________________________________
> plib-users mailing list
> pli...@li...
> https://lists.sourceforge.net/lists/listinfo/plib-users
>

Re: [Plib-users] Problem with rotations

[Steve B. <sjb...@ai...>]

Ben Woodhead wrote:
> I did read these articles but I will read them again. But I did use a matrix
> stack from the rotations and I am only rotating around 1 axe. If I change
> the code to just rotate around x it works, and if I change it to rotate
> around just z there is no problem, but just y causes some really weird
> results. Did you have a look at the code..

Sorry - no - I've been kinda busy.  I've seen *thousands* of cases of
objects rotating nicely around the Y axis - so I'm not inclined to suspect
a bug in PLIB...but anything's possible.

Just to be *sure*, I went into examples/src/ssg/tux/tux_example.cxx - and
changed the line:

   sgSetCoord ( & tuxpos, 0.0f,  0.0f, 0.0f, frameno, 0.0f, 0.0f ) ;

...and switched 'frameno' from Heading (Rotation about Z) to Roll (Rotation about Y):

   sgSetCoord ( & tuxpos, 0.0f,  0.0f, 0.0f, 0.0f, 0.0f, frameno ) ;

...and tux leans to the right, gradually disappears under the pedestal and
reappears on the left...exactly as I'd expect.

----------------------------- Steve Baker -------------------------------
Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
URLs : http://www.sjbaker.org
        http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
        http://prettypoly.sf.net http://freeglut.sf.net
        http://toobular.sf.net   http://lodestone.sf.net

Re: [Plib-users] Problem with rotations

[Ben W. <za...@ec...>]

I did read these articles but I will read them again. But I did use a matrix
stack from the rotations and I am only rotating around 1 axe. If I change
the code to just rotate around x it works, and if I change it to rotate
around just z there is no problem, but just y causes some really weird
results. Did you have a look at the code..

Thanks, Ben

----- Original Message -----
From: "Steve Baker" <sjb...@ai...>
To: <pli...@li...>
Sent: Monday, September 09, 2002 8:55 PM
Subject: Re: [Plib-users] Problem with rotations


> Ben Woodhead wrote:
>
> > I have moved the code into tux_example and removed the complexity and I
have
> > the same problem non the less.. Is there a bug releated to pitch.
>
> Sounds like a classic case of gymbal lock to me.
>
> Recommended reading:
>
>      http://www.sjbaker.org/steve/omniv/eulers_are_evil.html
>      http://www.sjbaker.org/steve/omniv/matrices_can_be_your_friends.html
>
>
> ----------------------------- Steve Baker -------------------------------
> Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
> URLs : http://www.sjbaker.org
>         http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
>         http://prettypoly.sf.net http://freeglut.sf.net
>         http://toobular.sf.net   http://lodestone.sf.net
>
>
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by: OSDN - Tired of that same old
> cell phone?  Get a new here for FREE!
> https://www.inphonic.com/r.asp?r=sourceforge1&refcode1=vs3390
> _______________________________________________
> plib-users mailing list
> pli...@li...
> https://lists.sourceforge.net/lists/listinfo/plib-users
>

Re: [Plib-users] Problem with rotations

[Steve B. <sjb...@ai...>]

Ben Woodhead wrote:

> I have moved the code into tux_example and removed the complexity and I have 
> the same problem non the less.. Is there a bug releated to pitch.

Sounds like a classic case of gymbal lock to me.

Recommended reading:

     http://www.sjbaker.org/steve/omniv/eulers_are_evil.html
     http://www.sjbaker.org/steve/omniv/matrices_can_be_your_friends.html


----------------------------- Steve Baker -------------------------------
Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
URLs : http://www.sjbaker.org
        http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
        http://prettypoly.sf.net http://freeglut.sf.net
        http://toobular.sf.net   http://lodestone.sf.net

Re: [Plib-users] Fw: "Could not find working GLU library" when compiling,

[Sebastian U. <ud...@ha...>]

On Mon, 9 Sep 2002, re...@ze... (Reed Hedges) wrote:
> Date: Mon, 9 Sep 2002 10:47:55 -0400
> To: pli...@li...
> From: re...@ze... (Reed Hedges)
> Reply-To: pli...@li...
> Subject: Re: [Plib-users] Fw: "Could not find working GLU library" when
> compiling,
>
>
> Does the  Plib configure script take a --with-glut option to add a 
> non-standard directory like that to the library paths?  That could be 
> useful:
>
>   ./configure --with-glut=/usr/X11R6/lib

It does:

  --with-GL=DIR           set the prefix directory where GL resides


- Sebastian

Re: [Plib-users] Fw: "Could not find working GLU library" when compiling,

[Reed H. <re...@ze...>]

Does the  Plib configure script take a --with-glut option to add a 
non-standard directory like that to the library paths?  That could be 
useful:

  ./configure --with-glut=/usr/X11R6/lib

>
> When trying to run the .configure script for PLIB 1.6.0 on my system
> running Linux Mandrake 8.2, the script got to an error:
> Could not find working GLU library

Re: [Plib-users] Fw: "Could not find working GLU library" when compiling,

[Kieran O'C. <ki...@ti...>]

----- Original Message -----
From: Steve Baker <sjb...@ai...>
To: <pli...@li...>
Sent: Sunday, September 08, 2002 1:08 PM
Subject: Re: [Plib-users] Fw: "Could not find working GLU library" when
compiling,


> Kieran O'Callaghan wrote:
> > I am not actually having this problem anymore.  I figured it out.  The
> > instructions on downloading and installing PLIB on the PLIB site
> > helped point me in the right direction. It always bothers me,
> > however, when someone writes to simply create a symbolic link in
> > one directory to the library file for X in another directory without
> > giving the slightest hint what the files themselves may be named.
>
> The problem is that the files are *not* in the right place.  Given they
> are not where they are supposed to be, it's just a matter of guesswork
> as to where they actually got installed.  So giving definitive statements
> as to where to link to is impossible.

I got that the files were not in the right place from the download and
installation page.  It said that they should be under /usr/lib and that
some distros still put them under /usr/X11R6/lib, which is not following
the standard.  Without that information, I would have been completely
lost.  Sorry if I was unclear.  The directions are about as clear as can
be expected really.  The only thing I thought might help a little in the
search was actually knowing the names of the libraries: libGLU.so.1
and libglut.so.1.  They are a little hard to find without knowing the
name beforehand.  Not incredibly so, but enough to discourage
someone who is not willing to spend a little bit of time on it with
no promise of success.  The fact that one has caps in the name and
the other does not can lead to a bit of frustration.
In any case, I have been working in tech support and I keep on
getting people who have been speaking to another tech who gave
them detailed instructions about what to do to solve the problem.
Then, the poor confused user calls back saying things like:  "Baaa,
baaa.  I downloaded the file, now what do I do?"  Baaa, baaa.
Then I consult the notes for the persons case and they are along
the lines of "user had a problem.  Told user how to fix problem",
with no mention of any fixes that were suggested.   You would
think that I could work backwards from the file name of the file
the person downloaded, but they usually do not actually know the
file name, nor do they know where to look to find the file, nor can
they tell me where they got it, nor can they tell me the air speed
velocity of an unladen swallow.  So, whenever I run into a
problem, I like to make notes about it, and I just thought that
someone might benifit from those notes.
That's the only reason I put that on this list.
Anyway.  I've babbled enough.
Since you're obviously reading this list, I might as well add:
Thanks for the great games Steve.

Ok, I'm off.

> > After installing that, the .configure script worked.  Possibly all those
> > manual symbolic links I made would have been completely unneccessary if
> > I had installed those RPMS to begin with.  In any case, it works now.
>
> There *is* a standard for where those files are supposed to be (it's
> called "The OpenGL ABI for Linux") - however some of the older distro's
> didn't adhere to it.
>
> ----------------------------- Steve Baker -------------------------------
> Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
> URLs : http://www.sjbaker.org
>         http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
>         http://prettypoly.sf.net http://freeglut.sf.net
>         http://toobular.sf.net   http://lodestone.sf.net
>
>
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by: OSDN - Tired of that same old
> cell phone?  Get a new here for FREE!
> https://www.inphonic.com/r.asp?r=sourceforge1&refcode1=vs3390
> _______________________________________________
> plib-users mailing list
> pli...@li...
> https://lists.sourceforge.net/lists/listinfo/plib-users

Re: [Plib-users] Problem with rotations

[Ben W. <be...@ec...>]

Hello Everybody=20

I have moved the code into tux_example and removed the complexity and I h=
ave=20
the same problem non the less.. Is there a bug releated to pitch.=20

Here is the file
Ben

[Plib-users] Problem with rotations

[Ben W. <be...@ec...>]

Hello Everybody

I ran into a little problem, and I am unable to resolve it. Basically I a=
m=20
just trying to rotate something around its axes. At different times. For =
x=20
and z this works perfectly but for y it does not.=20
The model start with its feet on the origin and rotates around the x axes=
, and=20
it does that but not completely. Once it flat (z =3D 0) then it jumps so =
that=20
the x axes is now going though the middle of it, and its feet are on the =
y=20
axes. It then completes half a rotation and jumps back and completes the=20
orignal rotation with is feet on the x axes.

function rotate (float h, float p, float r) {
  sgMat4 moveMat;
  sgMat4 newMat;
  sgMat4 currentLocation;

  sgCoord newCoord;

  sgMakeRotMat4(moveMat,h,p,r);
  sgMakeCoordMat4(currentLocation, & this->location);
  sgMultMat4(newMat,moveMat, currentLocation);

  sgSetCoord ( &newCoord, newMat ) ;
  this->location.xyz[0] =3D newCoord.xyz[0];
  this->location.xyz[1] =3D newCoord.xyz[1];
  this->location.xyz[2] =3D newCoord.xyz[2];
  this->location.hpr[0] =3D newCoord.hpr[0];
  this->location.hpr[1] =3D newCoord.hpr[1];
  this->location.hpr[2] =3D newCoord.hpr[2];
  this->setTransform( & this->location );
}

Re: [Plib-users] Fw: "Could not find working GLU library" when compiling,

[Steve B. <sjb...@ai...>]

Kieran O'Callaghan wrote:
> I am not actually having this problem anymore.  I figured it out.  The
> instructions on downloading and installing PLIB on the PLIB site
> helped point me in the right direction. It always bothers me,
> however, when someone writes to simply create a symbolic link in
> one directory to the library file for X in another directory without
> giving the slightest hint what the files themselves may be named.

The problem is that the files are *not* in the right place.  Given they
are not where they are supposed to be, it's just a matter of guesswork
as to where they actually got installed.  So giving definitive statements
as to where to link to is impossible.

> After installing that, the .configure script worked.  Possibly all those
> manual symbolic links I made would have been completely unneccessary if
> I had installed those RPMS to begin with.  In any case, it works now.

There *is* a standard for where those files are supposed to be (it's
called "The OpenGL ABI for Linux") - however some of the older distro's
didn't adhere to it.

----------------------------- Steve Baker -------------------------------
Mail : <sjb...@ai...>   WorkMail: <sj...@li...>
URLs : http://www.sjbaker.org
        http://plib.sf.net http://tuxaqfh.sf.net http://tuxkart.sf.net
        http://prettypoly.sf.net http://freeglut.sf.net
        http://toobular.sf.net   http://lodestone.sf.net

Re: [Plib-users] Fw: "Could not find working GLU library" when compiling,

[Ben W. <za...@ec...>]

One more thing, I forgot to mention. OpenGL is not part of X, its used by x,
but opengl does not need x. You can use opengl without x, although this does
not happen very often.

Ben

----- Original Message -----
From: "Kieran O'Callaghan" <ki...@ti...>
To: <pli...@li...>
Sent: Sunday, September 08, 2002 4:48 AM
Subject: [Plib-users] Fw: "Could not find working GLU library" when
compiling,


> I am not actually having this problem anymore.  I figured it out.  The
> instructions on downloading and installing PLIB on the PLIB site
> helped point me in the right direction. It always bothers me,
> however, when someone writes to simply create a symbolic link in
> one directory to the library file for X in another directory without
> giving the slightest hint what the files themselves may be named.
> Sure, I can figure out, but it's much easier to find out from someone
> who already knows.  Anyway, one of the places I checked for help
> on this was the mailing list archive.  I could not find anything, but
> maybe my search was not as complete as it could have been.  In
> any case, I am putting the entry I made into my own system log
> here, so that it might possibly help someone out in future.  I
> probably will not post to this list again, so signing up for the list may
> be slight overkill.  I suppose I could have asked someone on the list
> to post it for me, but that would have required that I know someone
> on the list, which probably requires me to already be on the list....
> Anyway...
>
> When trying to run the .configure script for PLIB 1.6.0 on my system
> running Linux Mandrake 8.2, the script got to an error:
> Could not find working GLU library
>
> In order to get PLIB 1.6.0 to compile correctly, had to create some
symbolic
> links for several library files:
> cd /usr/lib
> ln -s /usr/X11R6/lib/libGLU.so.1 libGLU.so.1
> ln -s libGLU.so.1 libGLU.so
> ln -s /usr/X11R6/lib/libglut.so.3 libglut.so.3
> ln -s libglut.so.3 libglut.so
> That took care of most of the problems with the .configure script of PLIB,
> but it also complained about glut.h.  It is supposed to be in
> /usr/include/GL, but it is not there.  It is also not in
> /usr/X11R6/include/GL, which is where I hoped to find it.  Discovered that
> the missing file is in the libMesaglut3-devel.rpm, which was not
installed.
> Installed it, it required libMesaGLU1-devel-4.0.1-4mdk.rpm to be installed
> as a dependency.  Installed that as well.
>
> After installing that, the .configure script worked.  Possibly all those
> manual symbolic links I made would have been completely unneccessary if
> I had installed those RPMS to begin with.  In any case, it works now.
>
>
>
>
> -------------------------------------------------------
> This sf.net email is sponsored by: OSDN - Tired of that same old
> cell phone?  Get a new here for FREE!
> https://www.inphonic.com/r.asp?r=sourceforge1&refcode1=vs3390
> _______________________________________________
> plib-users mailing list
> pli...@li...
> https://lists.sourceforge.net/lists/listinfo/plib-users
>