plib-users

[Plib-users] DAG issues

[Rahul C. <rah...@ya...>]

Steve:

Thanks for the clarification. I noticed that any node
thats derived from ssgEntity can have multiple
parents. Doesn't it mean that a scene graph
represented by SSG is not necessarily a Directed
Acyclic Graph ? What are the implications of this ?

I thought we only need geometry nodes (ssgLeafs) to
have multiple parents for instancing purpose. Please
let me know your thoughts. (any one who is interested)

--Rahul



--- Steve Baker <sjb...@ai...> wrote:
> Steve Baker wrote:
> 
> > > But think about a scenario where a Branch group
> has a
> > > leaf ssgRahulLeaf which is derived from ssgLeaf
> and
> > > has a different constrcutor which does not
> invoke
> > > recalcBSphere in it. Also imagine that the user
> of the
> > > ssg API did not call flatten on the scene graph
> before
> > > renedering it. Will the bounding spheres of the
> branch
> > > nodes be updated in this case ?
> 
> Oops - missed that comment.
> 
> If you fail to tell ssgRahulLeaf to do a
> recalcBSphere
> then the leaf node's bsphere will not have been
> computed,
> and (in theory) the first time the node is called
> upon to
> getBSphere, it *should* be computed.  That will
> typically
> happen the first time the scene graph is rendered.
> 
> I noticed though that ssgEntity (the base class for
> all
> scene graph nodes) does not dirty the sphere in its
> constructor function - so if you really did do that,
> things would be a little undefined.
> 
> I just fixed that by setting invalidBSphere TRUE in
> the ssgEntity constructor.
> 
> -- 
> Steve Baker                 
> http://web2.airmail.net/sjbaker1
> sjb...@ai... (home) 
> http://www.woodsoup.org/~sbaker
> sj...@ht...      (work)
> 
> _______________________________________________
> plib-users mailing list
> pli...@li...
>
http://lists.sourceforge.net/mailman/listinfo/plib-users
> 
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RE: [Plib-users] error in compile

[Pete H. <pet...@st...>]

Fixed!

As you suspected, libglut.a was still in my Mesa src directory. I made a link
in /usr/lib and it all worked fine. 

Thanks guys.

Pete

FROM: Steve Baker
DATE: 02/28/2000 23:09:35
SUBJECT: RE:  [Plib-users] error in compile



Norman Vine wrote:
> 
> Pete Hodgson writes:
> >
> >I`m having trouble compiling PLIB 1.0.20 Mandrake 7 Linux.
> >
> >`./configure` works fine, but when I run `make` it chokes
> >compiling simple.cxx,
> >talking about loads of undefined references to glut functions (i.e.
> >glutInitWindowSize, glutPassiveMotionFunc etc.) I have got
> >glut installed, and
> >it`s worked fine with other stuff. Could anybody possibly
> >shead any light on
> >the reason for this? TIA
> >
> 
> Try adding
> 
> -DGLUT_IS_PRESENT
> 
> to the gcc command line
> 
> Steve changed things recently to have a choice between
> the glut or the freeglut libraries

I don`t think that`s the case for PLIB 1.0.20, (I made *that*
mistake in 1.1.6 and fixed it in 1.1.7).  It`s more likely
that GLUT is installed somewhere weird.

What did the output from ./configure say?
(You may need to remove config.cache to see it re-run properly)

Where is glut.h and libglut.a?  I`d expect them to be in
/usr/include/GL/glut.h and /usr/lib/libglut.a

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

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Re: [Plib-users] <<code review>> Bounding sphere of a branch node

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

Steve Baker wrote:

> > But think about a scenario where a Branch group has a
> > leaf ssgRahulLeaf which is derived from ssgLeaf and
> > has a different constrcutor which does not invoke
> > recalcBSphere in it. Also imagine that the user of the
> > ssg API did not call flatten on the scene graph before
> > renedering it. Will the bounding spheres of the branch
> > nodes be updated in this case ?

Oops - missed that comment.

If you fail to tell ssgRahulLeaf to do a recalcBSphere
then the leaf node's bsphere will not have been computed,
and (in theory) the first time the node is called upon to
getBSphere, it *should* be computed.  That will typically
happen the first time the scene graph is rendered.

I noticed though that ssgEntity (the base class for all
scene graph nodes) does not dirty the sphere in its
constructor function - so if you really did do that,
things would be a little undefined.

I just fixed that by setting invalidBSphere TRUE in
the ssgEntity constructor.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

Re: [Plib-users] <<code review>> Bounding sphere of a branch node

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

Rahul Choudhury wrote:

> The current ssg code marks a branch node's bouding
> sphere empty as and when an entity is added to the
> branch or removed from it. But the bounding sphere of
> the branch node really does not get updated. The
> places where it does get updated are in flatten() of
> ssgOptimiser or the constructor of ssgLeaf (which in
> turn calls the recalcBSphere of ssgBranch).
> 
> But think about a scenario where a Branch group has a
> leaf ssgRahulLeaf which is derived from ssgLeaf and
> has a different constrcutor which does not invoke
> recalcBSphere in it. Also imagine that the user of the
> ssg API did not call flatten on the scene graph before
> renedering it. Will the bounding spheres of the branch
> nodes be updated in this case ?
> 
> Is this better to update the bounding sphere of a
> branch node right when an entity is added to or
> removed from it ?

I don't exactly mark the sphere 'empty' - I mark it
'dirty' (ie invalid) - and SSG will recompute it
only when something asks for the value of the bsphere.

The thing to bear in mind is that dirtying a bounding
sphere also dirties the spheres above it in the scene
graph.

What SSG does is to only recompute a bsphere when it's
actually needed.

That gives you LARGE speedups when a lot of leaf nodes
are dirtied between each update because the higher up
nodes are not repeatedly recomputed.

In general, bspheres will get recomputed a minimal number
of times in the CullAndDraw routine - or the next isect
request or whatever.

Clever - eh!

One of the keys to fast scene graph API's is 'lazy evaluation'.
 
> Let me know your views.

I think I dodged *that* bullet :-)

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

Re: [Plib-users] <<Code review>> ssgEntity::isectTest ( sgSphere *s, sgMat4 m, int testNeeded )

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

Rahul Choudhury wrote:

> sgVec3 center_vec ;
> float sum_radii = s->getRadius() + tmp.getRadius() ;
> sgSubVec3 ( center_vec, s->getCenter(),
> tmp.getCenter() ) ;
> 
> if ( center_vec[0] > sum_radii ||
>    center_vec[1] > sum_radii ||
>    center_vec[2] > sum_radii ) {
>         return SSG_OUTSIDE ;
>    }
> 
> I think the last line should be modified to
> take absolute values of center_vec[0],
> center_vec[1] and center_vec[2]

Yep - I think you are right about that one.
 
> Next thing ssg code does is taking squares
> of each of the radius, adding them and
> compares them with the square of the
> distances between the centers
> 
> Or in other words, it says
> if d^2 >= radiousOne^2 + radiousTwo^2
> then the given sphere lies outside the
> entity. (here d is the distance
> between the two centers of spheres,
> radiousOne is the radius of the
> entity sphere and radiousTwo is the
> radius of second sphere).
> 
> In stead I think we should say
> if d^2 >= (radiousOne + radiousTwo)^2
> or d >= (radiousOne + radiousTwo)
> then the given sphere lies outside the
> entity.

I think I could save time by saying:

  d^2 >= (r1+r2)^2

...but in order to use:

  d >= r1+r2

...I'd have to compute d using a sqrt(). Since
a sqrt is MUCH slower than a multiply (or even the
TWO multiplies I actually did) - it's more efficient
to compare the squares of the ranges than the ranges
themselves.

However, if I compute (r1+r2)^2, and that test fails
then I'd have to compute r1^2 and r2^2 later.  It's
a fine line as to which would be more efficient - and
it depends mainly on the statistics of sphere-to-sphere
contacts.

Good catch on the first one though - the code would
never have broken - but it will be faster with your
change.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

Re: [Plib-users] error in compile

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

Norman Vine wrote:
> 
> Pete Hodgson writes:
> >
> >I'm having trouble compiling PLIB 1.0.20 Mandrake 7 Linux.
> >
> >'./configure' works fine, but when I run 'make' it chokes
> >compiling simple.cxx,
> >talking about loads of undefined references to glut functions (i.e.
> >glutInitWindowSize, glutPassiveMotionFunc etc.) I have got
> >glut installed, and
> >it's worked fine with other stuff. Could anybody possibly
> >shead any light on
> >the reason for this? TIA
> >
> 
> Try adding
> 
> -DGLUT_IS_PRESENT
> 
> to the gcc command line
> 
> Steve changed things recently to have a choice between
> the glut or the freeglut libraries

I don't think that's the case for PLIB 1.0.20, (I made *that*
mistake in 1.1.6 and fixed it in 1.1.7).  It's more likely
that GLUT is installed somewhere weird.

What did the output from ./configure say?
(You may need to remove config.cache to see it re-run properly)

Where is glut.h and libglut.a?  I'd expect them to be in
/usr/include/GL/glut.h and /usr/lib/libglut.a

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

[Plib-users] <<code review>> Bounding sphere of a branch node

[Rahul C. <rah...@ya...>]

Hi Guys:

The current ssg code marks a branch node's bouding
sphere empty as and when an entity is added to the
branch or removed from it. But the bounding sphere of
the branch node really does not get updated. The
places where it does get updated are in flatten() of
ssgOptimiser or the constructor of ssgLeaf (which in
turn calls the recalcBSphere of ssgBranch).

But think about a scenario where a Branch group has a
leaf ssgRahulLeaf which is derived from ssgLeaf and
has a different constrcutor which does not invoke
recalcBSphere in it. Also imagine that the user of the
ssg API did not call flatten on the scene graph before
renedering it. Will the bounding spheres of the branch
nodes be updated in this case ?

Is this better to update the bounding sphere of a
branch node right when an entity is added to or
removed from it ?

Let me know your views.

--Rahul
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[Plib-users] <<Code review>> ssgEntity::isectTest ( sgSphere *s, sgMat4 m, int testNeeded )

[Rahul C. <rah...@ya...>]

I was just going through the code of SSG and saw
something interesting in the following:

ssgCullResult ssgEntity::isectTest ( sgSphere  *s,
sgMat4 m, int testNeeded )

In the above member function you are 
finding out the delta distances (in x, y and z
direction) between the centers of two 
spheres and trying to see whether delta
distance in any direction is greater 
than the sum of the radii.

The code currently looks like:

sgVec3 center_vec ;
float sum_radii = s->getRadius() + tmp.getRadius() ;
sgSubVec3 ( center_vec, s->getCenter(),
tmp.getCenter() ) ;

if ( center_vec[0] > sum_radii ||
   center_vec[1] > sum_radii ||
   center_vec[2] > sum_radii ) {
	return SSG_OUTSIDE ;
   }



I think the last line should be modified to 
take absolute values of center_vec[0], 
center_vec[1] and center_vec[2]



Next thing ssg code does is taking squares 
of each of the radius, adding them and 
compares them with the square of the 
distances between the centers

Or in other words, it says 
if d^2 >= radiousOne^2 + radiousTwo^2 
then the given sphere lies outside the 
entity. (here d is the distance 
between the two centers of spheres, 
radiousOne is the radius of the 
entity sphere and radiousTwo is the 
radius of second sphere).

In stead I think we should say
if d^2 >= (radiousOne + radiousTwo)^2 
or d >= (radiousOne + radiousTwo)
then the given sphere lies outside the 
entity.

In other words the distance between the
center of two spheres should be more 
than or equal to the summation of radii
of two spheres for the sphere to be 
disjoint.


Please let me know your thoughts on this.

-- Rahul


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RE: [Plib-users] error in compile

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

Pete Hodgson writes:
>
>I'm having trouble compiling PLIB 1.0.20 Mandrake 7 Linux. 
>
>'./configure' works fine, but when I run 'make' it chokes 
>compiling simple.cxx,
>talking about loads of undefined references to glut functions (i.e.
>glutInitWindowSize, glutPassiveMotionFunc etc.) I have got 
>glut installed, and
>it's worked fine with other stuff. Could anybody possibly 
>shead any light on
>the reason for this? TIA
>

Try adding

-DGLUT_IS_PRESENT

to the gcc command line

Steve changed things recently to have a choice between
the glut or the freeglut libraries

Norman

[Plib-users] error in compile

[Pete H. <pet...@st...>]

Hi All.

I'm having trouble compiling PLIB 1.0.20 Mandrake 7 Linux. 

'./configure' works fine, but when I run 'make' it chokes compiling simple.cxx,
talking about loads of undefined references to glut functions (i.e.
glutInitWindowSize, glutPassiveMotionFunc etc.) I have got glut installed, and
it's worked fine with other stuff. Could anybody possibly shead any light on
the reason for this? TIA

Pete

PS I can send the full stderr output if it is helpful.

Re: [Plib-users] ssg coordinate system convention

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

Paul Bleisch wrote:
> 
> Hey Steve,
> 
> Where does the "Z is up" affect code?  i.e. "Z is up" to me
> means that there are assumptions in the code like "the 'floor'
> is in the XY plane", "gravity has the unit vector (0,0,-1)",
> and such.  It could also affect what roll, pitch and yaw mean.

That's the main difference.  There are a couple of routines
in SSG that know which way is up....but the noticable difference
is that an unrotated camera looks down the Y axis with Z pointing
up.

Note though that when I load a file from (say) a '.ac' file (which
has a marked Y-is-up bias), I do the necessary conversions such
that things look the same in AC3D as they do in SSG.

> (But I thought there were de facto standards for that in the
> vizsim industry.  Are they Z is up?)

Yes.  YAW means rotation around the Z axis, PITCH means rotation
about X and ROLL means rotation about Y.  In SSG and SG, I talk
about 'Heading' instead of 'Yaw' because the word Yaw starts with
a 'Y' and that can get confused with the Y axis. H,P and R are
mercifully unused for other common graphics coordinates.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

RE: [Plib-users] ssg coordinate system convention

[Paul B. <pbl...@di...>]

Hey Steve,

Where does the "Z is up" affect code?  i.e. "Z is up" to me 
means that there are assumptions in the code like "the 'floor' 
is in the XY plane", "gravity has the unit vector (0,0,-1)",
and such.  It could also affect what roll, pitch and yaw mean.
(But I thought there were de facto standards for that in the
vizsim industry.  Are they Z is up?)

It's been a while since I was in the ssg code, so this may
seem obvious to others.  


Thanks,
Paul


> -----Original Message-----
> From: Steve Baker [mailto:sjb...@ai...]
> Sent: Wednesday, February 23, 2000 11:50 PM
> To: pli...@li...
> Subject: Re: [Plib-users] ssg coordinate system convention
> 
> 
> Rahul Choudhury wrote:
> > 
> > Just started looking into the ssg src code. I was
> > wondering whether the coordinate system convention
> > used in SSG is same as OpenGL or something different.
> 
> SSG's coordinate system is the same 'handedness' as OpenGL,
> but uses Z-is-up instead of Y-is-up.   I'm afraid that's
> because I come from a flight simulation background (where
> Z-is-up has always been the convention) - and there are really
> too many users to change it at this late stage.
> 
> SSG is not alone in this - SGI's Performer scene graph library
> is also a Z-is-up system that's based on OpenGL.
> 
> -- 
> Steve Baker                  http://web2.airmail.net/sjbaker1
> sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
> sj...@ht...      (work)
> 
> _______________________________________________
> plib-users mailing list
> pli...@li...
> http://lists.sourceforge.net/mailman/listinfo/plib-users
> 

Re: [Plib-users] ssg coordinate system convention

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

Rahul Choudhury wrote:
> 
> Just started looking into the ssg src code. I was
> wondering whether the coordinate system convention
> used in SSG is same as OpenGL or something different.

SSG's coordinate system is the same 'handedness' as OpenGL,
but uses Z-is-up instead of Y-is-up.   I'm afraid that's
because I come from a flight simulation background (where
Z-is-up has always been the convention) - and there are really
too many users to change it at this late stage.

SSG is not alone in this - SGI's Performer scene graph library
is also a Z-is-up system that's based on OpenGL.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

[Plib-users] ssg coordinate system convention

[Rahul C. <rah...@ya...>]

Just started looking into the ssg src code. I was
wondering whether the coordinate system convention
used in SSG is same as OpenGL or something different.

OpenGL uses something like: (provided my spaces remain
in place:)

                Y(positive)
                |
                |
                |
                |
                |
                |
		-------------- X (positive)
               /
              /
             /
            /
           /
          Z (positive)

--Rahul
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Re: [Plib-users] odd text question

[Sylvan C. <si...@si...>]

Steve Baker wrote:
> 
> Hmmmm - are you using the SLANT range (ie using Pythagoras) or the 
> simple Z distance (ie measured at right angles to the plane of the 
> screen)?

thanks a bunch :) i was using the slant range (doh).

> Hence FNT should work perfectly once you've figured out what
> to do with all the matrices!

and indeed it does!

-s

Re: [Plib-users] odd text question

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

Sylvan Clebsch wrote:
> 
> i have an odd text usage question that i'm hoping someone might be able
> to help me with. what i'd like to do is have text labels on objects in
> the scene, indicating information about that object.
> 
> my first pass at this was to use gluProject to derive the window
> coordinates, and then render text with fntRenderer and an orthographic
> projection matrix. the result was perfect in all but one way: i don't
> want labels to appear for objects which are behind other objects. in
> other words, i'd very much like to be able to render the text at the
> same depth as the object, so that it gets obscured by closer objects in
> the scene graph.
> 
> hack as i might (including writing my own text renderer), i found no way
> to match up the depth buffer.

No - that would be almost impossible.  There isn't a good way to relate
what an 'orthographic Z' would be to the corresponding 'perspective Z'...
and it might even be implementation dependent.

> i tried finding the z distance from the
> camera to the object, drawing the text with that z distance and not
> clearing the depth buffer and such, but it seems that once i switch to
> the orthographic projection matrix, i can't get anything i draw to be
> obscured by anything else drawn in the frame.

Yep - exactly.
 
> i then tried rendering the text as 3d text, rotating it to face the
> camera and scaling it based on the inverse of the distance in order to
> get it to maintain a uniform size.

That seems like by far the best idea.

> this works, but of course perspective
> text simply isn't orthographic text; it changes size noticeably from the
> center of the viewport to the edge of the viewport.

Hmmmm - are you using the SLANT range (ie using Pythagoras) or the simple
Z distance (ie measured at right angles to the plane of the screen)?

It seems to me that you should be using the latter - and you are using the
former - which would account for the problem.
 
> if anyone has any ideas, even if it means not using fntRenderer or
> extending it drastically, i'd very much appreciate it. thanks.

Well, the FNT library draws text in the 3D position and point size
you tell it to - it knows nothing about ortho, perspective or anything
else.  Hence FNT should work perfectly once you've figured out what
to do with all the matrices!

No matter what is the final solution, FNT should be useful to you.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

[Plib-users] odd text question

[Sylvan C. <si...@si...>]

i have an odd text usage question that i'm hoping someone might be able
to help me with. what i'd like to do is have text labels on objects in
the scene, indicating information about that object.

my first pass at this was to use gluProject to derive the window
coordinates, and then render text with fntRenderer and an orthographic
projection matrix. the result was perfect in all but one way: i don't
want labels to appear for objects which are behind other objects. in
other words, i'd very much like to be able to render the text at the
same depth as the object, so that it gets obscured by closer objects in
the scene graph.

hack as i might (including writing my own text renderer), i found no way
to match up the depth buffer. i tried finding the z distance from the
camera to the object, drawing the text with that z distance and not
clearing the depth buffer and such, but it seems that once i switch to
the orthographic projection matrix, i can't get anything i draw to be
obscured by anything else drawn in the frame.

i then tried rendering the text as 3d text, rotating it to face the
camera and scaling it based on the inverse of the distance in order to
get it to maintain a uniform size. this works, but of course perspective
text simply isn't orthographic text; it changes size noticeably from the
center of the viewport to the edge of the viewport.

if anyone has any ideas, even if it means not using fntRenderer or
extending it drastically, i'd very much appreciate it. thanks.

-s

Re: [Plib-users] Problem loading VRML files using ssg

[Dave M. <dp...@ef...>]

Rahul Choudhury wrote:

> I tried with around 8/9 vrml files, but could not load
> any.

I asked about this on plib-devel too and Steve said
the VRML is not working.  Still under development.

Were you mainly interested in VRML 1.0 ascii ?
If so, I'm planning on writing a loader for that in
the short term.

--Dave

Re: [Plib-users] Problem loading VRML files using ssg

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

Rahul Choudhury wrote:
> 
> Hi,
> 
> Yesterday I downloaded few VRML files from the net and
> was trying to load them using SSG. When I opened the
> VRML files in text editor, they looked normal. But ssg
> failed to load them and gave exception (probably
> because of some null pointer some where). Did any one
> of you guys face this problem ?

Yes - sorry, the VRML loader that comes with PLIB certainly
doesn't work - I should probably take it out of the distribution.

There have been many efforts to come up with a good VRML-1 loader
capability - but so far none of them have been really sucessful.

There is a VRML-97 loader out there that seems to work for
some VRML-97 (aka VRML-2) files - but it won't load VRML-1
and IMHO it's a pain to install so it's not included in the
distro.

Since PLIB is now being used with the Pretty Poly modeller,
there has been renewed interest in getting a good VRML loader
working - I don't know the exact timescale - but if you monitor
the plib-announce or plib-devel mailing lists, you'll get a
better heads-up on that one.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

[Plib-users] Problem loading VRML files using ssg

[Rahul C. <rah...@ya...>]

Hi,

Yesterday I downloaded few VRML files from the net and
was trying to load them using SSG. When I opened the
VRML files in text editor, they looked normal. But ssg
failed to load them and gave exception (probably
because of some null pointer some where). Did any one
of you guys face this problem ?

I only changed the load_datebase() method of
tux_example.cxx that comes with ssg. 
In staed of the following line,
ssgEntity *tux_obj = ssgLoadAC ( "tuxedo.ac"   ) ;

I added, 
ssgEntity *tux_obj = ssgLoadVRML ( "f117.wrl"   ) ;

I tried with around 8/9 vrml files, but could not load
any. You can download some lightweight vrml files from
the following URL ( I dont want to clutter up your
mail box by sending few as attachments):

http://iaehv.nl/users/wbergmns/jetvrml.htm

Please let me know if you have any solution.
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Re: [Plib-users] Input Library

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

Ryujin Doraegon wrote:
> 
> Hello, i'm looking for a library that help me manage user input from a keyboard
> or joystick but with some special features.

Well, PLIB has a joystick library that makes reading the current position
quite easy - but to decide which "move" was made via some complex sequence
of joystick actions is beyond what we do.

I seriously doubt you'll find a package that'll have those features
directly - but it wouldn't be to hard to write.

You'd have to decide exactly which parts of the joystick range constitute "down"
(the joystick axes go from -1 to +1 - so "down" could mean "any Y value less
than -0.5"...say).

You could split the ranges of the joystick into (say) 8 regions with a neutral
region in the middle:

  int where_is_the_stick ( float x, float y )
  {
    if ( y > 0.5 )
    {
       if ( x < -0.5 ) return TOP_LEFT  ;
       if ( x >  0.5 ) return TOP_RIGHT ;
       return TOP_CENTER ;
    }

    if ( y < -0.5 )
    {
       if ( x < -0.5 ) return BOTTOM_LEFT  ;
       if ( x >  0.5 ) return BOTTOM_RIGHT ;
       return BOTTOM_CENTER ;
    }

    if ( x < -0.5 ) return LEFT  ;
    if ( x >  0.5 ) return RIGHT ;
    return NEUTRAL ; 
  }

...call that routine every frame to catagorize the position.
Every time the joystick CHANGES position compared to last frame,
store that in an array that holds (say) the last 20 places the
joystick visited.

Now, whenever you add an entry into that array, you can compare
the last few locations the joystick was at against a table of
"moves" that your game needs to recognise.

So, "Hit forwards twice" would be when you've seen NEUTRAL/TOP/NEUTRAL/TOP/NEUTRAL
and "Moved in a semicircle" would be BOTTOM/BOTTOM-LEFT/LEFT/TOP-LEFT/TOP or
something. You'll probably need to recognise several combinations of functions
for each move because he may start his semicircle at BOTTOM-LEFT instead of
BOTTOM - and you probably don't want the moves to have to be TOO exact.

> im using OpenGL and the GLUT Library, it seems that GLUT doesn't support this
> features.

I don't think any library does - you have to write it yourself.

> Another thing is that i don want the keyboard autorepeat feature,
> when i press a key i want it pressed until i release it.

You can turn off autorepeat in GLUT. Just call glutIgnoreKeyRepeat().

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

[Plib-users] Input Library

[Ryujin D. <ry...@ca...>]

Hello, i'm looking for a library that help me manage user input from a keyboard
or joystick but with some special features.

To make it simple i want a set of functions that allow me to make moves like
those we see in figthing games like Street Figther or Tekken,  i mean that when
i hit foward twice quickly the player performs a quick dash, and when hitting
back twice quickly it makes a little bakwards jump.  Performing a semicircle
move (back, back-down, down, down-foward, foward) and pressing action the player
performs an special attack etc.

There is a lot of more advanced things i need for the game im writing, things
like when dashing foward and pressing jump it performs a high jump instead of a
normal jump. 

im using OpenGL and the GLUT Library, it seems that GLUT doesn't support this
features. Another thing is that i don want the keyboard autorepeat feature,
when i press a key i want it pressed until i release it.

If someone havi information o how i can do this with plib , GLUT , SDL or any
library please let me know.

Thanks

Re: [Plib-users] FNT text rendering on Matrox G200

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

Paolo Leoncini wrote:
> 
> Did anyone faced a dirty rendering (i.e. grey rects in place of text characters) of FNT library texture-mapped text strings on a Matrox G200 w driver 5.30 (the latest as far as I know)? I experienced it in running both the library example and FlightGear 0.7.1a.

There was a bug in the G200/G400 driver that caused this a long time back - I
thought it had been fixed - but I could easily be wrong.

IIRC, it showed up in the FNT example program as one half of the texture map
(displayed in the bottom-left corner of the display) being 'trashed'.

> It might be obviously due to a problem in how texture mapping is mapped onto card's features by the current driver, but in other applications yet in the same configuration texture mapping is generally correct (+ high quality, good performances).

FNT uses monochrome (INTENSITY_ALPHA) maps with colour blend mode on the
texture map.  Not many programs do that - so we could easily be hitting a
poorly tested path.

I suggest you ask on the Mesa mailing list.  I subscribe to that list
so I can chime in with answers to PLIB-ish questions if they come up.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)

[Plib-users] FNT text rendering on Matrox G200

[Paolo L. <p.l...@ci...>]

Did anyone faced a dirty rendering (i.e. grey rects in place of text characters) of FNT library texture-mapped text strings on a Matrox G200 w driver 5.30 (the latest as far as I know)? I experienced it in running both the library example and FlightGear 0.7.1a.
It might be obviously due to a problem in how texture mapping is mapped onto card's features by the current driver, but in other applications yet in the same configuration texture mapping is generally correct (+ high quality, good performances).

Greetings to all -

-----------------------------------------------------------------------------
Paolo Leoncini				phone:  +39 (0823) 623134
Scientific Visualization Group			fax:    +39 (0823) 623126
CIRA - Italian Center for Aerospace Research	e-mail: p.l...@ci...
Via Maiorise - 81043 Capua (CE) Italy		http://www.cira.it/research/vis

[Plib-users] Mailing list move.

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

Mailing List Move.
~~~~~~~~~~~~~~~~~~

The Tux_AQFH and PLIB mailing lists are moving to the SourceForge
servers.  I have re-subscribed everyone who was subscribed to the
following lists:

   pli...@wo...
   pli...@wo...
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To the corresponding new lists:

   pli...@li...
   pli...@li...
   pli...@li...
   tux...@li...
   tux...@li...
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(Notice that there is no longer an underscore in tuxaqfh - that's
due to a bug in the SourceForge software).

To post to the list, just email to the lists above.  The 'announce'
lists are heavily moderated (by me) - so they'll basically only
contain major announcements.

To subscribe, unsubscribe, switch to digest-only mode or visit the
(currently empty!) archives, go to:

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My next step is to relocate the PLIB and Tux_AQFH web sites
to SourceForge - at which point, all this information will
be available from the web site.

Sorry for the incovenience.

        Steve.

-- 
Steve Baker                  http://web2.airmail.net/sjbaker1
sjb...@ai... (home)  http://www.woodsoup.org/~sbaker
sj...@ht...      (work)