plib-users

Re: [Plib-users] Having trouble with ./compile

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

"Martin L. Metke" wrote:
> 
> Hi!
>   I've been trying to get PLIB to ./compile and make for nearly a
> month, off and on, with the following problem:  on ./compiling, I'm
> told that PLIB can't find any GL commands or GLU/GLUT commands, but I
> can't find GLUT and FreeGLUT won't install either.  This is actually a
> step forward, however, because I had to track down and compile from
> scratch all the newest versions and libs of GCC/Glibc just to get to
> this point... and that's wreacked havoc on my system in and of itself,
> but that's another story.

Hmmm - what distro do you have?

I'm suprised that you'd need a particular GCC/Glibc unless your system
is *very* old.

>   Now, when I try to make from my compile, it gets as far as making
> pui, then pops up an error saying that it can't find glx.h, gl.h, or
> glu.h.  I assume this means that various OpenGL includes are not
> around,

Yes - or you have it installed in the wrong place.

You should have the following files:

   /usr/include/GL/gl.h
   /usr/include/GL/glu.h
   /usr/include/GL/glut.h

   /usr/lib/libGL.so.<version_numbers>
   /usr/lib/libGLU.so.<version_numbers>
   /usr/lib/libglut.so.<version_numbers>   ...or /usr/lib/libglut.a

You should *not* have other versions in other directories - you should
not have any libMesa<anything>'s...unless they are symbolic links to
the files above - or vice versa.  You should use the Linux 'find'
command to search out all the strange versions stuck in places like
/usr/local/lib, /usr/X11R6/lib and so on.  If you don't do that, you'll
find that some programs pick up the "correct" OpenGL/Mesa and others
will find ancient versions that have the wrong drivers or something.

Be *RUTHLESS*!

> but I know I have the latest Mesa or OpenGL, 'cause my Mandrake
> update disk has all the newest drivers on it.

Weeeeelllll.....*maybe*.

> Do I need to track down GLUT, or is this another problem?

GLUT is normally distributed with Mesa - and is probably on your
Mandrake distro.  Why it's not installed - I don't know.  Maybe
it *is* installed - but since the GLUT header #include's the
OpenGL headers, that could be enough to screw up the ./configure
script into thinking that GLUT isn't correctly installed.

You should also be able to get it from http://www.opengl.org - or
with Mesa at http://www.mesa3d.org...and as you said, "freeglut"
can be a reasonable replacement - get it at http://freeglut.sourceforge.net

However, freeglut won't install if your OpenGL is broken.

>   I'm looking forward to finally getting this library installed so I
> can try my hand at some flight simming on Linux :)

I can imagine!  But having your OpenGL/Mesa correctly installed is
an ESSENTIAL first step.

When you think you have it right - run some Mesa sample programs and
be sure you are actually getting hardware accelleration.  Once that's
working, try again with PLIB (and 'freeglut' if you want).

-- 
Steve Baker   HomeEmail: <sjb...@ai...>
              WorkEmail: <sj...@li...>
              HomePage : http://web2.airmail.net/sjbaker1
              Projects : http://plib.sourceforge.net
                         http://tuxaqfh.sourceforge.net
                         http://tuxkart.sourceforge.net
                         http://prettypoly.sourceforge.net
                         http://freeglut.sourceforge.net

[Plib-users] Having trouble with ./compile

[Martin L. M. <exa...@ba...>]

Hi!
  I've been trying to get PLIB to ./compile and make for nearly a 
month, off and on, with the following problem:  on ./compiling, I'm 
told that PLIB can't find any GL commands or GLU/GLUT commands, but I 
can't find GLUT and FreeGLUT won't install either.  This is actually a 
step forward, however, because I had to track down and compile from 
scratch all the newest versions and libs of GCC/Glibc just to get to 
this point... and that's wreacked havoc on my system in and of itself, 
but that's another story.
  Now, when I try to make from my compile, it gets as far as making 
pui, then pops up an error saying that it can't find glx.h, gl.h, or 
glu.h.  I assume this means that various OpenGL includes are not 
around, but I know I have the latest Mesa or OpenGL, 'cause my Mandrake 
update disk has all the newest drivers on it.  Do I need to track down 
GLUT, or is this another problem?
  I'm looking forward to finally getting this library installed so I 
can try my hand at some flight simming on Linux :)
  Thanks for your help,
Martin
-- 
---,-@

Martin L. Metke
Exa...@ba...
Sl...@ho...
"I laughed, I cried, I fell down, it changed my life... it was good!"

Re: [Plib-users] Semi-transparent plane

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

Martin Howard wrote:
> 
> Wolfram Kuss jotted down the following:
> 
> > Get a model with transparency,
> 
> OK, I tried this.  The cockpit of the Optica model is a solid grey, it is
> *not* transparent.  The glass looks like shiny grey plastic.  This is
> despite having the lines:
> 
>     glEnable(GL_BLEND);
>     glEnable(GL_DEPTH_TEST);
>     glEnable(GL_ALPHA_TEST);
> 
> in the global set-up portion of my code (just after ssgInit() is called).
> 
> I also tried Norman Vine's suggestion, using the state/material properties
> he posted here.  Again, no transparency, but I can alter the appearance of
> the (flat) plane by modifying the GL_EMISSION and GL_SPECULAR properties.
> But no transparency.  What's my next move?  I'm sorry to be harking on like
> this guys, but I can't make any sense of this and I really *need* this
> transparency thing working.

Running the models/flying_saucer.ac model from my TuxAQFH game (URL below)
in the examples/src/ssg/viewer program from the PLIB examples suite on CVS
DEFINITELY shows transparency.

One possiblity though is that some of the old RIVA graphics cards don't do
polygon alpha correctly (or at all in some cases) - if you have one of those
old clunkers then the fault is in OpenGL.

What graphics card and OpenGL library are you using BTW?


-- 
Steve Baker   HomeEmail: <sjb...@ai...>
              WorkEmail: <sj...@li...>
              HomePage : http://web2.airmail.net/sjbaker1
              Projects : http://plib.sourceforge.net
                         http://tuxaqfh.sourceforge.net
                         http://tuxkart.sourceforge.net
                         http://prettypoly.sourceforge.net
                         http://freeglut.sourceforge.net

[Plib-users] Re: [FGFS-Users] Error Compiling CVS

[John C. <j4s...@ro...>]

David,
I've been getting the same error with a 2.2. kernel.
If you use the -k switch when you build you can get past it
AFAIK fgfs doesn't use any of the methods in that bit.
I have noticed that aircraft models don't get painted
using this... dunno if it's related

J

On Fri, 19 Jan 2001, David Findlay wrote:

> I am getting an error in the CVS version. I am using Kernel 2.4 - could this
> be a problem?
>
> Making all in net
> make[2]: Entering directory `/home/david/flightgear/plib/src/net'
> c++ -DPACKAGE=\"plib\" -DVERSION=\"1.3.1\" -DHAVE_LIBDL=1 -DHAVE_LIBGL=1
> -DHAVE_LIBGLU=1 -DSTDC_HEADERS=1 -DHAVE_GL_GL_H=1 -DHAVE_GL_GLU_H=1
> -DLINUX_JOYSTICK_IS_PRESENT=1 -DGLUT_IS_PRESENT=1  -I. -I.  -I../../src/util
> -I/usr/local/include  -g -O2 -O6 -Wall -c netRoomMaster.cxx
> In file included from netRoomMaster.cxx:1:
> netRoomMaster.h: In method `class netRoomServerInfo *
> netRoomServerList::match(const netRoomServerInfo *)':
> netRoomMaster.h:43: implicit declaration of function `int stricmp(...)'
> make[2]: *** [netRoomMaster.o] Error 1
> make[2]: Leaving directory `/home/david/flightgear/plib/src/net'
> make[1]: *** [all-recursive] Error 1
> make[1]: Leaving directory `/home/david/flightgear/plib/src'
> make: *** [all-recursive] Error 1
>
> This is it. I haven't really looked into it yet.
>
> David
>
> --
> Please visit the FGFS web page:  http://www.flightgear.org
> For help on using this list (especially unsubscribing), send a message to
> "fgf...@fl..." with a single line of text: "help".
>

Re: [Plib-users] FNT and windows 95

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

> Scott Shumaker wrote:
> 
> Is this a windows 95 only problem?  I recently had a similar problem when adding
> fnt support to a small game project: for a while I wasn't getting fnt output at
> all.  I eventually traced it back to the fact that I was using a std::vector to
> store the texFnt objects

The acid test is "Does the FNT example program work?"

If it does then it's very likely that this is another application problem - if not
then we are probably looking at an OpenGL driver problem or something.  We've seen
quite a few problems like that - and they all  (so far) have turned out to be OpenGL
driver bugs.


-- 
Steve Baker   HomeEmail: <sjb...@ai...>
              WorkEmail: <sj...@li...>
              HomePage : http://web2.airmail.net/sjbaker1
              Projects : http://plib.sourceforge.net
                         http://tuxaqfh.sourceforge.net
                         http://tuxkart.sourceforge.net
                         http://prettypoly.sourceforge.net
                         http://freeglut.sourceforge.net

[Plib-users] Error Compiling CVS

[David F. <ne...@bi...>]

I am getting an error in the CVS version. I am using Kernel 2.4 - could this 
be a problem?

Making all in net
make[2]: Entering directory `/home/david/flightgear/plib/src/net'
c++ -DPACKAGE=\"plib\" -DVERSION=\"1.3.1\" -DHAVE_LIBDL=1 -DHAVE_LIBGL=1 
-DHAVE_LIBGLU=1 -DSTDC_HEADERS=1 -DHAVE_GL_GL_H=1 -DHAVE_GL_GLU_H=1 
-DLINUX_JOYSTICK_IS_PRESENT=1 -DGLUT_IS_PRESENT=1  -I. -I.  -I../../src/util  
-I/usr/local/include  -g -O2 -O6 -Wall -c netRoomMaster.cxx
In file included from netRoomMaster.cxx:1:
netRoomMaster.h: In method `class netRoomServerInfo * 
netRoomServerList::match(const netRoomServerInfo *)':
netRoomMaster.h:43: implicit declaration of function `int stricmp(...)'
make[2]: *** [netRoomMaster.o] Error 1
make[2]: Leaving directory `/home/david/flightgear/plib/src/net'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/david/flightgear/plib/src'
make: *** [all-recursive] Error 1

This is it. I haven't really looked into it yet.

David

[Plib-users] Translucency solved!

[Martin H. <how...@os...>]

OK, I did a search for "plib" and "transparent" in Google and got the PUI
programmer's guide (which I hadn't read: because I don't use it).  In there
is a heading "Transparent GUI's".  It suggests:

    * pick a default colour with an alpha component of about 0.4f.
    * call glEnable(GL_BLEND) and set up an appropriate blend function;
      the author suggests glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
      and using glAlphaFunc(GL_GREATER, 0.1f) -- the latter translates into
      using state->setAlphaClamp(0.1f).

So, in the *global* set-up portion of my program, I called glBlendFunc() and
whadd'ya know: I now have a beautiful semi-transparent plane.

In conclusion then: glBlendFunc() is *not* set up to some reasonable default
by PLIB -- at least not if you want to have transparent objects in your
scene.  Putting the glBlendFunc() in a preDraw() or postDraw() callback is
*not* sufficient to get the transparency to render correctly.  It needs to
go into the global set-up just after the call to ssgInit().

Finally, I'd like to extend a warm "thank you" to all who helped and to
those who developed and continue to develop PLIB.

M.

-- 
Martin Howard                    |
Visiting Scholar, CSEL, OSU      | The New Economy: Creating difficulties
email: how...@os...        | to sell solutions.
www: http://mvhoward.i.am/       +----------------------------------------

Re: [Plib-users] Semi-transparent plane

[Martin H. <how...@os...>]

Wolfram Kuss jotted down the following:

> Get a model with transparency,

OK, I tried this.  The cockpit of the Optica model is a solid grey, it is
*not* transparent.  The glass looks like shiny grey plastic.  This is
despite having the lines:

    glEnable(GL_BLEND);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_ALPHA_TEST);

in the global set-up portion of my code (just after ssgInit() is called).

I also tried Norman Vine's suggestion, using the state/material properties
he posted here.  Again, no transparency, but I can alter the appearance of
the (flat) plane by modifying the GL_EMISSION and GL_SPECULAR properties.
But no transparency.  What's my next move?  I'm sorry to be harking on like
this guys, but I can't make any sense of this and I really *need* this
transparency thing working.

M.

-- 
Martin Howard                     |
Visiting Scholar, CSEL, OSU       |     It is essentially contestable.
email: how...@os...         |
www: http://mvhoward.i.am/        +---------------------------------------

Re: [Plib-users] FNT and windows 95

[Scott S. <sjs...@um...>]

Is this a windows 95 only problem?  I recently had a similar problem =
when adding fnt support to a small game project: for a while I wasn't =
getting fnt output at all.  I eventually traced it back to the fact that =
I was using a std::vector to store the texFnt objects, and because of =
the way I was inserting them, a temporary was created and then =
destroyed, and their destructors were then getting called, which in turn =
deleted the font texture.  After fixing this, however, the fnt output =
seems to work fine on Win95 / 98 / 2000.  Can you link the problems to a =
particular driver / video card revision?
  ----- Original Message -----=20
  From: lafont02=20
  To: pli...@li...=20
  Sent: Thursday, January 18, 2001 1:12 AM
  Subject: [Plib-users] FNT and windows 95


  I have a bunch of users that are not able to display FNT text using =
windows 95.  Has there been a fix to this?  Or perhaps a workaround??

  Don.

Re: [Plib-users] Semi-transparent plane

[Wolfram K. <w_...@rz...>]

What you can try is:

Get a model with transparency, for example, on

http://home.t-online.de/home/Wolfram.Kuss

goto Misc Panes and download the optica.
Put Model (*.ac) and textures into the same dir.
=46rom your app, call ssgLoad, leaving the second parameter at NULL.
Put the model into your scene graph. IMHO this should then work,
without further code. If it does, you can either load a model for your
Semi-transparent plane too, or, if you want to do everything via code
and not files, then extract the necessary code from the loader.

Bye bye,
Wolfram.

RE: [Plib-users] Semi-transparent plane

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

Martin Howard writes:
>
>Quick summary: ssgSimpleState does indeed work for materials other than
>solid white, or textures.  I downloaded the source for TuxKart and TuxAQFH.
>They both use material.cxx and material.h to define materials.
> Translucent
>objects do:
>
>    state->setTranlucent();
>    state->enable(GL_ALPHA_TEST);
>    state->setAlphaClamp(alpha_ref);
>    state->enable(GL_BLEND);
>
>I do the same in my code now, but I either get a plane which is opaque, or
>not rendered at all, depending upon the value of the vertex colours to
>'alpha_ref' (alpha <= alpha_ref doesn't render).  If I don't call
>setAlphaClamp() at all, then I get an opaque plane.  Also, I'm no longer
>fiddling around with glBlendFunc() or glDepthMask(), but leaving them at
>whatever defaults SSG sets them to.  Drawing order appears to be correct,
>but I still don't get any translucency.
>
>Anyone got any other ideas?

-- untested --

state->enable( GL_LIGHTING ) ;
state->setShadeModel( GL_SMOOTH ) ;
state->enable( GL_COLOR_MATERIAL ) ;
state->setColourMaterial( GL_AMBIENT_AND_DIFFUSE ) ;
state->setMaterial( GL_EMISSION, 0.1, 0.31, 0.71, .4 ) ;
state->setMaterial( GL_SPECULAR, 0.31, 0.51, 0.91, .4 ) ;
state->setShininess( 0.8 ) ;
state->setTranslucent() ;
state->enable( GL_BLEND ) ;
state->enable ( GL_ALPHA_TEST ) ;
state->setAlphaClamp ( 0.0f ) ;

Norman

[Plib-users] FNT and windows 95

[lafont02 <laf...@cn...>]

I have a bunch of users that are not able to display FNT text using =
windows 95.  Has there been a fix to this?  Or perhaps a workaround??

Don.

Re: [Plib-users] Re: plib-users digest, Vol 1 #170 - 9 msgs

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

Stephen Lee wrote:
> 
> Hi, I'm a new user of plib and OpenGL in general, can i mix OpenGL commands
> with ssg ? e.g draw a cube using GL_QUADS ?

Yes!  This is a major design goal of SSG.  (It has to be like that
so that you can use multiple OpenGL libraries in the same
program - for example PLIB's SSG *and* FNT *and* PUI all in
the same program.

There are a *couple* of caveats.

  1) Changing 'state' in OpenGL (eg switching texture maps, using
     glEnable/glDisable, etc) can be quite costly in performance.
     Because of that, SSG uses 'lazy' state updates.  It keeps
     track of the current OpenGL state - and only changes the
     minimum of state settings when it has to.

     If you start messing around switching things on and off
     without telling SSG, it can get a little confused.

     There are three ways to fix that.

        * Be sure to glPushAttrib/glPopAttrib around your
          state changes - so that SSG's states are restored
          afterwards.

        * Don't do your own state switching at all. Use SSG
          for that. Create ssgSimpleState's and use the 'apply'
          member function to make that state be the current one.
          That way, SSG always knows the current state.

        * Do what the heck you like to the state - but be sure
          to call the 'force' member function of any ssgSimpleState
          before you give control back to SSG.  'force' is just
          like 'apply' except that it doesn't use lazy evaluation,
          it just unconditionally sets all the state elements.

     Which to do?  The answer is "it depends" - and unfortunately,
     there is no clear best solution.

  2) As with lazy state changes, we also have lazy matrix switching.
     Be sure to restore the modelview and projection matrices when
     you are done messing around.

One *cool* way to do this is to derive your own ssgLeaf class.  That
makes your OpenGL commands become a part of the SSG system and you
can let SSG deal with the uglinesses of field of view culling for you.

-- 
Steve Baker   HomeEmail: <sjb...@ai...>
              WorkEmail: <sj...@li...>
              HomePage : http://web2.airmail.net/sjbaker1
              Projects : http://plib.sourceforge.net
                         http://tuxaqfh.sourceforge.net
                         http://tuxkart.sourceforge.net
                         http://prettypoly.sourceforge.net
                         http://freeglut.sourceforge.net

Re: [Plib-users] Semi-transparent plane

[Martin H. <how...@os...>]

Steve Baker jotted down the following:

> Martin Howard wrote:
>> So, please, excuse a dumb beginner, but am I on the right track with
>> callbacks?  How do I control drawing order?
> 
> You don't need to do that.  SSG does it for you...just sit back and enjoy
> the ride!

Quick summary: ssgSimpleState does indeed work for materials other than
solid white, or textures.  I downloaded the source for TuxKart and TuxAQFH.
They both use material.cxx and material.h to define materials.  Translucent
objects do:

    state->setTranlucent();
    state->enable(GL_ALPHA_TEST);
    state->setAlphaClamp(alpha_ref);
    state->enable(GL_BLEND);

I do the same in my code now, but I either get a plane which is opaque, or
not rendered at all, depending upon the value of the vertex colours to
'alpha_ref' (alpha <= alpha_ref doesn't render).  If I don't call
setAlphaClamp() at all, then I get an opaque plane.  Also, I'm no longer
fiddling around with glBlendFunc() or glDepthMask(), but leaving them at
whatever defaults SSG sets them to.  Drawing order appears to be correct,
but I still don't get any translucency.

Anyone got any other ideas?

M. 

-- 
Martin Howard               | "Why do I think that MacOS is better than
Visiting Scholar, CSEL, OSU | Windows? Well, you can put sideburns and
email: how...@os...   | shades on a 50-year old guy...but that still
www: http://mvhoward.i.am/  | don't make him Elvis"  -- Unknown
                            +--------------------------------------------

[Plib-users] Re: plib-users digest, Vol 1 #170 - 9 msgs

[Stephen L. <sl...@si...>]

Hi, I'm a new user of plib and OpenGL in general, can i mix OpenGL commands
with ssg ? e.g draw a cube using GL_QUADS ?

Re: [Plib-users] Scaling loaded models - clipping problems

[Per L. <li...@ho...>]

On Wednesday 17 January 2001 13:52, Sam Stickland wrote:
> Hi,
>
> I'm having some difficultly scaling loaded models in SSG.  I have an model
> in AC3D format that I wish to draw in various sizes about the scene.  So my
> first thought is to load the model, and then stick relevant scaling
> transforms above it.
>
> a 0 0 0
> 0 a 0 0
> 0 0 a 0
> 0 0 0 1
>
> to scale by a in all three axis.  But I get clipping problems when I do
> this.  It appears that SSG isn't updating the bounding sphere? (I've tried
> calling recalcBSphere() on the returned entity from ssgLoadAC). Am I doing
> anything obviously wrong here?

What I did when I needed a scaled version of a model, was that I loaded it, 
scaled it (and presumably got the same clip-problems that you do), but just 
saved the scaled model as an ASE model. This format doesn't store normals or 
bounding spheres, so these will be recalculated when you load the model the 
next time, and it will work as expected. Works all right, if you can live 
with that the scaling is done off-line.

I'm not sure it will work in your application, since I don't know what you 
want to do with the model.

Regards,
Per

-- 
   / Per Liedman
  / li...@ho...
 / www.mdstud.chalmers.se/~md6pl
/ 031-825659 / 0705-520455

Re: [Plib-users] Semi-transparent plane

[Wolfram K. <w_...@rz...>]

"Ben Discoe" <be...@wa...> wrote:

>ssgSimpleState would be just fine for your translucent object, if it =
worked.
>That class, and material properties in general, are not actually =
functional
>in PLIB/SSG.

Wrong.

>If you look at the applications using SSG, you'll see that the majority =
of
>them use entirely textured objects - the underlying material usually =
being a
>solid white per-vertex color,=20

That is indeed true for the majority of things, but the minority of
faces that are untextured, coloured work. I "played" with lots of
planes from Micro$oft Flight Simulator. They use much white, textured
faces as well. But several have, for example, untextured, coloured
spinners. These work. The only problem I know of is that .ASE loader
and/or writer doesnt work with this and the same is true for .AC, as I
found out just yesterday evening :-(.

We are working on the loaders/writers.
Apart from that, ssgSimpleState works.

Regarding transparency: Quite a lot of the airplanes have transparent
cockpits. This works as well.

>For actual use of material properties, including translucency, you may =
want
>to look at other scene graph APIs, such as OSG,
>http://www.openscenegraph.org/

Why? If you really know of a bug apart from .ASE and .AC, then please
tell it to us, since we are working towards PLIB 1.4.0, that is, a
stable version.


>
>-Ben
>http://vterrain.org/

Bye bye,
Wolfram.

Re: [Plib-users] Scaling loaded models - clipping problems

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

Sam Stickland wrote:
> 
> Hi,
> 
> I'm having some difficultly scaling loaded models in SSG.  I have an model
> in AC3D format that I wish to draw in various sizes about the scene.  So my
> first thought is to load the model, and then stick relevant scaling
> transforms above it.
> 
> a 0 0 0
> 0 a 0 0
> 0 0 a 0
> 0 0 0 1
> 
> to scale by a in all three axis.  But I get clipping problems when I do
> this.  It appears that SSG isn't updating the bounding sphere? (I've tried
> calling recalcBSphere() on the returned entity from ssgLoadAC). Am I doing
> anything obviously wrong here?

Yeah - scaling is kinda *broken* in SSG.  It turns out to be a real pain
to implement because there isn't an easy way to maintain the bounding
spheres during scaling without clobbering the performance of non-scaled
models.

I suggest running the ssgFlatten command which multiplies out transforms...
or better still, just write a little tree walk that visits all the leaf
nodes and multiplies all the vertices by 'a'.

Scaling is generally a bad idea in OpenGL anyway because your vertex normals
are scaled by the matrix too - that screws up your lighting.  You can glEnable
the renormalize flag (I forget the token name) - but that incurs an extra
sqrt per vertex - which is pretty serious in itself - and in many OpenGL
implementations, this throws you off the 'optimised path' and your program
runs 50x slower or something awful.

We should really remove scaling from the SSG API - but then you wouldn't
be able to pass us an arbitary matrix - and that's too useful.

This needs to be mentioned in the manual.

-- 
Steve Baker   HomeEmail: <sjb...@ai...>
              WorkEmail: <sj...@li...>
              HomePage : http://web2.airmail.net/sjbaker1
              Projects : http://plib.sourceforge.net
                         http://tuxaqfh.sourceforge.net
                         http://tuxkart.sourceforge.net
                         http://prettypoly.sourceforge.net
                         http://freeglut.sourceforge.net

Re: [Plib-users] Semi-transparent plane

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

Ben Discoe wrote:
> 
> > -----Original Message-----
> > From: Martin Howard
> >
> > I've been struggling for about a week trying to get a
> > semi-transparent plane to show using SSG. [...]
> >
> > it would appear that ssgSimpleState cannot achieve the
> > effects on its own: I need callbacks that
> > call 'glBlendFunc()' and 'glDepthMask()'.
> 
> ssgSimpleState would be just fine for your translucent object, if it worked.
> That class, and material properties in general, are not actually functional
> in PLIB/SSG.

Well, if that's true then it's something someone has broken quite recently.

I use this stuff all the time and it works OK for me.

> If you look at the applications using SSG, you'll see that the majority of
> them use entirely textured objects - the underlying material usually being a
> solid white per-vertex color, the only kind of color supported by SSG.

That's not true.  Look at TuxAQFH for example.  The spaceship on the 'moon'
level, the waterfall in the training level, the glass cube on the race level,
etc all work just fine.
 
> For actual use of material properties, including translucency, you may want
> to look at other scene graph APIs, such as OSG,
> http://www.openscenegraph.org/

Ben: Please check your facts before advising people to use other libraries.
If you hate PLIB that much - get the heck off the mailing list.

-- 
Steve Baker   HomeEmail: <sjb...@ai...>
              WorkEmail: <sj...@li...>
              HomePage : http://web2.airmail.net/sjbaker1
              Projects : http://plib.sourceforge.net
                         http://tuxaqfh.sourceforge.net
                         http://tuxkart.sourceforge.net
                         http://prettypoly.sourceforge.net
                         http://freeglut.sourceforge.net

Re: [Plib-users] Semi-transparent plane

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

Martin Howard wrote:

> I have the Red Book, and the OpenGL Superbible and I've read the PLIB
> documentation on the web site.  From what I can tell, you need to draw
> everything else before you draw the translucent plane, but I don't know how
> to achive this with SSG (I tried adding the plane as the last child to the
> scene, but it doens't seem to work).

SSG knows that translucent things have to be drawn last...and it does it
automatically on your behalf.

>  Also, it would appear that
> ssgSimpleState cannot achieve the effects on its own: I need callbacks that
> call 'glBlendFunc()' and 'glDepthMask()'.

glBlendFunc is set to a 'sensible' value by default - you shouldn't need
to tough glDepthMask in this application.
 
> So, please, excuse a dumb beginner, but am I on the right track with
> callbacks?  How do I control drawing order?

You don't need to do that.  SSG does it for you...just sit back and enjoy
the ride!

>  And am I missing anything
> obvious?  As it is, my transluscent plane isn't being drawn at all.

Then I *suspect* you have something else wrong.  Maybe it's back-facing?
Maybe it's alpha is too low to show up?  It's hard to tell without seeing
the code.
 
-- 
Steve Baker   HomeEmail: <sjb...@ai...>
              WorkEmail: <sj...@li...>
              HomePage : http://web2.airmail.net/sjbaker1
              Projects : http://plib.sourceforge.net
                         http://tuxaqfh.sourceforge.net
                         http://tuxkart.sourceforge.net
                         http://prettypoly.sourceforge.net
                         http://freeglut.sourceforge.net

[Plib-users] Scaling loaded models - clipping problems

[Sam S. <sa...@sp...>]

Hi,

I'm having some difficultly scaling loaded models in SSG.  I have an model
in AC3D format that I wish to draw in various sizes about the scene.  So my
first thought is to load the model, and then stick relevant scaling
transforms above it.

a 0 0 0
0 a 0 0
0 0 a 0
0 0 0 1

to scale by a in all three axis.  But I get clipping problems when I do
this.  It appears that SSG isn't updating the bounding sphere? (I've tried
calling recalcBSphere() on the returned entity from ssgLoadAC). Am I doing
anything obviously wrong here?

Sam

RE: [Plib-users] Semi-transparent plane

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

Martin Howard writes:
>
>I've been struggling for about a week trying to get a semi-transparent
plane
>to show using SSG.

Mark Valleland posted some code showing one way of doing this
by adding translucent polgons on top of the track in Steve's tuxkart game
http://tuxkart.sourceforge.net

Here is a link to Mark's message describing this
http://www.geocrawler.com/archives/3/3037/2000/7/0/4033334/

there is a link to the actual code in the archived message

Cheers

Norman

RE: [Plib-users] Semi-transparent plane

[Ben D. <be...@wa...>]

> -----Original Message-----
> From: Martin Howard
>
> I've been struggling for about a week trying to get a
> semi-transparent plane to show using SSG. [...]
>
> it would appear that ssgSimpleState cannot achieve the
> effects on its own: I need callbacks that
> call 'glBlendFunc()' and 'glDepthMask()'.

ssgSimpleState would be just fine for your translucent object, if it worked.
That class, and material properties in general, are not actually functional
in PLIB/SSG.

If you look at the applications using SSG, you'll see that the majority of
them use entirely textured objects - the underlying material usually being a
solid white per-vertex color, the only kind of color supported by SSG.

For actual use of material properties, including translucency, you may want
to look at other scene graph APIs, such as OSG,
http://www.openscenegraph.org/

-Ben
http://vterrain.org/

[Plib-users] Semi-transparent plane

[Martin H. <how...@os...>]

I've been struggling for about a week trying to get a semi-transparent plane
to show using SSG.  First off, I'm primarily an HCI guy with programming
skills which I use for prototype production, and not primarily a programmer.
I took the Tux demo and transmogrified it into a display where there is a
textured ground plane, a camera at a certain altitude above that plane, and
a number of objects scattered at different heights in the field of view.
What I want to achieve is a semi-transparent plane just under the camera's
altitude, parallel to the ground plane, with a slight colour tint:
everything under that plane would be slightly dimmer and slightly colour
tinted (as if viewed through tinted glass), everything above would be
unobstructed.  Objects cut in half by the translucent plane would be
rendered accordingly.  (I'm doing this as part of my research on 3D
displays, so I'm not really interested in the prototype itself beyond being
able to run experiments with it as a stimulus.)

I have the Red Book, and the OpenGL Superbible and I've read the PLIB
documentation on the web site.  From what I can tell, you need to draw
everything else before you draw the translucent plane, but I don't know how
to achive this with SSG (I tried adding the plane as the last child to the
scene, but it doens't seem to work).  Also, it would appear that
ssgSimpleState cannot achieve the effects on its own: I need callbacks that
call 'glBlendFunc()' and 'glDepthMask()'.

So, please, excuse a dumb beginner, but am I on the right track with
callbacks?  How do I control drawing order?  And am I missing anything
obvious?  As it is, my transluscent plane isn't being drawn at all.

M.

-- 
Martin Howard                    |
Visiting Scholar, CSEL, OSU      |         53 kB/s and nothing on.
email: how...@os...        |
www: http://mvhoward.i.am/       +----------------------------------------

Re: [Plib-users] Does anyone use .ssg files?

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

Wolfram Kuss wrote:
> 
> Steve wrote:
> 
> >Wolfram Kuss wrote:
> >>
> >> Does anyone use files in plib's own ".ssg"-format?
> >
> >Yes - but not for long-term model storage.
> 
> Keeping .SSG reading and writing compatible would have bloated the
> code too much, so we made a break and trying to read .SSG file format
> version zero leads to an error. For more see plib-devel or the docs
> (in non_class.html).

That's fine by me.

However, we DO need a stable file format that we can both read and write
reliably (such that repeated read/write cycles don't change the model too).

I don't think SSG is yet that format (because it's not 100% stable).

-- 
Steve Baker   HomeEmail: <sjb...@ai...>
              WorkEmail: <sj...@li...>
              HomePage : http://web2.airmail.net/sjbaker1
              Projects : http://plib.sourceforge.net
                         http://tuxaqfh.sourceforge.net
                         http://tuxkart.sourceforge.net
                         http://prettypoly.sourceforge.net
                         http://freeglut.sourceforge.net