Re: zbuffer() & zwritemask in Performer

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Gordon Tomlinson (gordon++at++paradigmsim.com)
Tue, 20 Jul 1999 15:51:39 -0500

Hi

Under OpenGL you use

     glDepthFunc( zfunc );
     glDisable( GL_DEPTH_TEST) ;
     glEnable( GL_DEPTH_TEST) ;

G.

Jorge Valencia Loera wrote:

> Hi pf's,
>
> my configuration:
>
> Onyx
> 12 x R4440 CPUs
> 2 x RE2 w/ MCO on each pipe
> IRIX 6.5.3
> PF 2.2.4
> I use multiple processes, multiple channels, multiple pipes & I link my app
> using Iris GL.
>
> Does anybody know about performer functions (Libpr routines I guess) that
> can do the same work as the GL functions zbuffer() & zwritemask() ???
>
> I am working on a space simulation and I am trying to draw a background
> first (the sun, moon & earth) without writing into the depth buffer (to
> avoid problems w/ the shadow map when casting shadows) & on top of that draw
> a foreground (the space station)
>
> my scene graph is something like this:
> (use a regular font to see the scene graph)
>
> SCENE
> / \
> / \
> BG FG
> /\ \
> / |\ \
> / | \ \
> / | \ \
> STARS SUN MOON SPACE
> STATION
>
> The "background - foreground" effect is working fine but when I try to cast
> shadows I have some color corruption (there is some transparency appearing
> on the space station so that I can see my background through some objects)
> and the shadows are completely wrong!!! (I only see some sort of big
> randomized shadow on the screen)
>
> I guess it's because my background is still blowing up my depth buffer. If I
> remove the BG sub-tree from my scene graph then everything works fine.
>
> I use the following node callbacks for my BG node:
>
> // This function is called during traversal just before drawing a
> // celestial body node. Its purpose is to disable the writing to
> // the Z buffer.
> int
> BGPreDrawCB(pfTraverser *_trav, void *_data)
> {
> zbuffer( FALSE );
> zwritemask( 0 );
>
> return PFTRAV_CONT;
> }
>
> // This function is called during traversal just after drawing a
> // celestial body node. Its purpose is to enable the writing to
> // the Z buffer.
> int
> BGPostDrawCB(pfTraverser *_trav, void *_data)
> {
> zbuffer( TRUE );
> zwritemask( 0xFFFFFFFF );
>
> return PFTRAV_CONT;
> }
>
> I think that the internal libpr record concerning the graphics state is not
> updated due to the fact that I set the graphics state directly through the
> GL so may be libpr is making incorrect assumptions about the current
> graphics state.
>
> or am I doing something wrong?
> Is there a better way to do what I want to do?
> Does anybody know about something related to my problem
>
> Any help, comment,... will be really appreciated.
> Thank you.
>
> Jorge.
>
> ______________________________________________________
> Get Your Private, Free Email at http://www.hotmail.com
> -----------------------------------------------------------------------
> List Archives, FAQ, FTP: http://www.sgi.com/software/performer/
> Submissions: info-performer++at++sgi.com
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--


Regards


Gordon.


Gordon Tomlinson              | Multigen - Paradigm  Inc
Vega Software Engineer        | Suite 400, 14900 Landmark Blvd
Email: gordon++at++paradigmsim.com | Dallas, Texas 75240, USA
Tel:    972 960 2301          | Fax:    972 960 2303
______________________________________________________________


'Smoke me a kipper skipper, I'll be back for breakfast'
______________________________________________________________


640K of ram should enough for anybody. Bill Gates 1981


There is no reason anyone would want a computer in their home
           (Ken Olson, president of Digital Equip Corp 1977 )
______________________________________________________________










 

Hi

Under OpenGL you use

 

     glDepthFunc(  zfunc );

     glDisable( GL_DEPTH_TEST) ;

     glEnable( GL_DEPTH_TEST) ;

 

 

G.

 

Jorge Valencia Loera wrote:

Hi pf's,

my configuration:

Onyx

12 x R4440 CPUs

2 x RE2 w/ MCO on each pipe

IRIX 6.5.3

PF   2.2.4

I use multiple processes, multiple channels, multiple pipes & I
link my app

using Iris GL.

Does anybody know about performer functions (Libpr routines I guess)
that

can do the same work as the GL functions zbuffer() & zwritemask()
???

I am working on a space simulation and I am trying to draw a background

first (the sun, moon & earth) without writing into the depth buffer
(to

avoid problems w/ the shadow map when casting shadows) & on top
of that draw

a foreground (the space station)

my scene graph is something like this:

(use a regular font to see the scene graph)

      SCENE

       /  \

      /    \

     BG    FG

     /\      \

    / |\      \

   /  | \      \

  /   |  \      \

STARS SUN MOON  SPACE

               
STATION

The "background - foreground" effect is working fine but when I try
to cast

shadows I have some color corruption (there is some transparency appearing

on the space station so that I can see my background through some objects)

and the shadows are completely wrong!!! (I only see some sort of big

randomized shadow on the screen)

I guess it's because my background is still blowing up my depth buffer.
If I

remove the BG sub-tree from my scene graph then everything works fine.

I use the following node callbacks for my BG node:

// This function is called during traversal just before drawing a

// celestial body node. Its purpose is to disable the writing to

// the Z buffer.

int

BGPreDrawCB(pfTraverser *_trav, void *_data)

{

  zbuffer( FALSE );

  zwritemask( 0 );

  return PFTRAV_CONT;

}

// This function is called during traversal just after drawing a

// celestial body node. Its purpose is to enable the writing to

// the Z buffer.

int

BGPostDrawCB(pfTraverser *_trav, void *_data)

{

  zbuffer( TRUE );

  zwritemask( 0xFFFFFFFF );

  return PFTRAV_CONT;

}

I think that the internal libpr record concerning the graphics state
is not

updated due to the fact that I set the graphics state directly through
the

GL so may be libpr is making incorrect assumptions about the current

graphics state.

or am I doing something wrong?

Is there a better way to do what I want to do?

Does anybody know about something related to my problem

Any help, comment,... will be really appreciated.

Thank you.

Jorge.

______________________________________________________

Get Your Private, Free Email at http://www.hotmail.com

-----------------------------------------------------------------------

List Archives, FAQ, FTP:  http://www.sgi.com/software/performer/

           
Submissions:  info-performer++at++sgi.com

        Admin. requests:  info-performer-request++at++sgi.com



-- 


Regards

Gordon.


Gordon Tomlinson              | Multigen - Paradigm  Inc
Vega Software Engineer        | Suite 400, 14900 Landmark Blvd
Email: gordon++at++paradigmsim.com | Dallas, Texas 75240, USA
Tel:    972 960 2301          | Fax:    972 960 2303  
______________________________________________________________

'Smoke me a kipper skipper, I'll be back for breakfast'         
______________________________________________________________

640K of ram should enough for anybody. Bill Gates 1981

There is no reason anyone would want a computer in their home
           (Ken Olson, president of Digital Equip Corp 1977 )
______________________________________________________________

 

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