Thread: Re: [PyOpenGL-Users] get Translation inside matrix stack

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Re: [PyOpenGL-Users] get Translation inside matrix stack

From: Prashant S. <ani...@ya...> - 2008-07-22 16:32:22

I am sorry but I didn't get any success with your code. I tried this:

glPushMatrix()
glTranslate(5,0,0)
glTranslate(10,0,0)
glTranslate(5,0,0)
# To get total increment of x axis(which is 5+10+5=20) 
modelview = glGetFloatv( GL_MODELVIEW_MATRIX )
print modelview
glPopMatrix()

but I am getting this:
[[1.0, 0.0, 0.0, 0.0], [0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 1.0, 0.0], [0.0, 0.0, 0.0, 1.0]]
Which does,'t solve my problem.


----- Original Message ----
From: Prashant Saxena <ani...@ya...>
To: Gary Herron <gh...@is...>
Sent: Tuesday, July 22, 2008 9:59:38 PM
Subject: Re: [PyOpenGL-Users] get Translation inside matrix stack


I am sorry but I didn't get any success with your code. I tried this:

glPushMatrix()
glTranslate(5,0,0)
glTranslate(10,0,0)
glTranslate(5,0,0)
# To get total increment of x axis(which is 5+10+5=20) 
modelview = glGetFloatv( GL_MODELVIEW_MATRIX )
print modelview
glPopMatrix()

but I am getting this:
[[1.0, 0.0, 0.0, 0.0], [0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 1.0, 0.0], [0.0, 0.0, 0.0, 1.0]]
Which does,'t solve my problem.




----- Original Message ----
From: Gary Herron <gh...@is...>
Cc: pyo...@li...
Sent: Tuesday, July 22, 2008 8:48:24 PM
Subject: Re: [PyOpenGL-Users] get Translation inside matrix stack

Shantytown Saxena wrote:
>
> glPushMatrix()
> glTranslate(5,0,0)
> glTranslate(10,0,0)
> glTranslate(5,0,0)
> # How do I get here total increment of x axis(which is 5+10+5=20) 
> before I Pop up.
> glPopMatrix()

All the transformations are recorded by OpenGL in a 4x4 matrix.
You can recover that matrix like this:

    buff = (ctypes.c_double*16)()
    pyglet.gl.glGetDoublev(stack, buff)

If you started with the identity and did no other transformations you'll 
find the 20 in that 4x4 array.

In either the [0,3] or [3,0] element.  (I've forgotten which way Opengl 
stores the array now.)

Gary Herron


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Re: [PyOpenGL-Users] get Translation inside matrix stack

From: Black <py...@bl...> - 2008-07-22 19:18:30

When you use build a display list using GL_COMPILE, the various state  
variables aren't affected, the commands themselves are just being  
stored. Since glGet is one of the commands that isn't stored, it gets  
executed immediately and you have the problem you are seeing.

You can try GL_COMPILE_AND_EXECUTE. I tend not to use it as it doesn't  
work on the system that I use, but it might work for you. Since it is  
executing the OpenGL commands as they are stored, glGet should get the  
correct result. The bigger question to ask is what you are using the  
information for? The glGet won't be stored, so the effect will be the  
same as keeping track of it yourself. However, if you are trying to  
get changing behavior out of your display list based on conditions  
outside of it, display lists are probably not the right answer anyway...



On Jul 22, 2008, at 1:12 PM, Prashant Saxena wrote:

> Thanks,
>
> Yes, I am doing this inside the glNewList(GL_COMPILE).
> Is there any way to solve the problem or do I calculate manually?
>
>
> ----- Original Message ----
> From: Black <py...@bl...>
> To: pyo...@li...
> Sent: Tuesday, July 22, 2008 10:24:27 PM
> Subject: Re: [PyOpenGL-Users] get Translation inside matrix stack
>
> Two quick things to check:
> a) Is the MODELVIEW matrix the current matrix (i.e., the one being
> affected by the glTranslates)?
>     If not, well, it should be
> b) Are you doing this while constructing a display list with
> glNewList(GL_COMPILE)?
>     If so, the matrix isn't being updated and this won't work
>
> On Jul 22, 2008, at 12:32 PM, Prashant Saxena wrote:
>
> > I am sorry but I didn't get any success with your code. I tried  
> this:
> >
> > glPushMatrix()
> > glTranslate(5,0,0)
> > glTranslate(10,0,0)
> > glTranslate(5,0,0)
> > # To get total increment of x axis(which is 5+10+5=20)
> > modelview = glGetFloatv( GL_MODELVIEW_MATRIX )
> > print modelview
> > glPopMatrix()
> >
> > but I am getting this:
> > [[1.0, 0.0, 0.0, 0.0], [0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 1.0, 0.0],
> > [0.0, 0.0, 0.0, 1.0]]
> > Which does,'t solve my problem.
> >
> > ----- Original Message ----
> > From: Prashant Saxena <ani...@ya...>
> > To: Gary Herron <gh...@is...>
> > Sent: Tuesday, July 22, 2008 9:59:38 PM
> > Subject: Re: [PyOpenGL-Users] get Translation inside matrix stack
> >
> > I am sorry but I didn't get any success with your code. I tried  
> this:
> >
> > glPushMatrix()
> > glTranslate(5,0,0)
> > glTranslate(10,0,0)
> > glTranslate(5,0,0)
> > # To get total increment of x axis(which is 5+10+5=20)
> > modelview = glGetFloatv( GL_MODELVIEW_MATRIX )
> > print modelview
> > glPopMatrix()
> >
> > but I am getting this:
> > [[1.0, 0.0, 0.0, 0.0], [0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 1.0, 0.0],
> > [0.0, 0.0, 0.0, 1.0]]
> > Which does,'t solve my problem.
> >
> >
> > ----- Original Message ----
> > From: Gary Herron <gh...@is...>
> > Cc: pyo...@li...
> > Sent: Tuesday, July 22, 2008 8:48:24 PM
> > Subject: Re: [PyOpenGL-Users] get Translation inside matrix stack
> >
> > Shantytown Saxena wrote:
> > >
> > > glPushMatrix()
> > > glTranslate(5,0,0)
> > > glTranslate(10,0,0)
> > > glTranslate(5,0,0)
> > > # How do I get here total increment of x axis(which is 5+10+5=20)
> > > before I Pop up.
> > > glPopMatrix()
> >
> > All the transformations are recorded by OpenGL in a 4x4 matrix.
> > You can recover that matrix like this:
> >
> >    buff = (ctypes.c_double*16)()
> >    pyglet.gl.glGetDoublev(stack, buff)
> >
> > If you started with the identity and did no other transformations
> > you'll
> > find the 20 in that 4x4 array.
> >
> > In either the [0,3] or [3,0] element.  (I've forgotten which way
> > Opengl
> > stores the array now.)
> >
> > Gary Herron
> >
> >
> > >
> > >
> >  
> ------------------------------------------------------------------------
> > >
> > >
> >  
> -------------------------------------------------------------------------
> > > This SF.Net email is sponsored by the Moblin Your Move Developer's
> > challenge
> > > Build the coolest Linux based applications with Moblin SDK & win
> > great prizes
> > > Grand prize is a trip for two to an Open Source event anywhere in
> > the world
> > > http://moblin-contest.org/redirect.php?banner_id=100&url=/
> > >
> >  
> ------------------------------------------------------------------------
> > >
> > > _______________________________________________
> > > PyOpenGL Homepage
> > > http://pyopengl.sourceforge.net
> > > _______________________________________________
> > > PyOpenGL-Users mailing list
> > > PyO...@li...
> > > https://lists.sourceforge.net/lists/listinfo/pyopengl-users
> > >
> >
> >
> >  
> -------------------------------------------------------------------------
> > This SF.Net email is sponsored by the Moblin Your Move Developer's
> > challenge
> > Build the coolest Linux based applications with Moblin SDK & win
> > great prizes
> > Grand prize is a trip for two to an Open Source event anywhere in
> > the world
> > http://moblin-contest.org/redirect.php?banner_id=100&url=/
> > _______________________________________________
> > PyOpenGL Homepage
> > http://pyopengl.sourceforge.net
> > _______________________________________________
> > PyOpenGL-Users mailing list
> > PyO...@li...
> > https://lists.sourceforge.net/lists/listinfo/pyopengl-users
> >
> >
> >  
> -------------------------------------------------------------------------
> > This SF.Net email is sponsored by the Moblin Your Move Developer's
> > challenge
> > Build the coolest Linux based applications with Moblin SDK & win
> > great prizes
> > Grand prize is a trip for two to an Open Source event anywhere in
> > the world
> > http://moblin-contest.org/redirect.php?banner_id=100&url=/_______________________________________________
> > PyOpenGL Homepage
> > http://pyopengl.sourceforge.net
> > _______________________________________________
> > PyOpenGL-Users mailing list
> > PyO...@li...
> > https://lists.sourceforge.net/lists/listinfo/pyopengl-users
>
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's  
> challenge
> Build the coolest Linux based applications with Moblin SDK & win  
> great prizes
> Grand prize is a trip for two to an Open Source event anywhere in  
> the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
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> _______________________________________________
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> https://lists.sourceforge.net/lists/listinfo/pyopengl-users
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>

Re: [PyOpenGL-Users] get Translation inside matrix stack

From: Black <py...@bl...> - 2008-07-22 16:54:23

Two quick things to check:
a) Is the MODELVIEW matrix the current matrix (i.e., the one being  
affected by the glTranslates)?
	If not, well, it should be
b) Are you doing this while constructing a display list with  
glNewList(GL_COMPILE)?
	If so, the matrix isn't being updated and this won't work

On Jul 22, 2008, at 12:32 PM, Prashant Saxena wrote:

> I am sorry but I didn't get any success with your code. I tried this:
>
> glPushMatrix()
> glTranslate(5,0,0)
> glTranslate(10,0,0)
> glTranslate(5,0,0)
> # To get total increment of x axis(which is 5+10+5=20)
> modelview = glGetFloatv( GL_MODELVIEW_MATRIX )
> print modelview
> glPopMatrix()
>
> but I am getting this:
> [[1.0, 0.0, 0.0, 0.0], [0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 1.0, 0.0],  
> [0.0, 0.0, 0.0, 1.0]]
> Which does,'t solve my problem.
>
> ----- Original Message ----
> From: Prashant Saxena <ani...@ya...>
> To: Gary Herron <gh...@is...>
> Sent: Tuesday, July 22, 2008 9:59:38 PM
> Subject: Re: [PyOpenGL-Users] get Translation inside matrix stack
>
> I am sorry but I didn't get any success with your code. I tried this:
>
> glPushMatrix()
> glTranslate(5,0,0)
> glTranslate(10,0,0)
> glTranslate(5,0,0)
> # To get total increment of x axis(which is 5+10+5=20)
> modelview = glGetFloatv( GL_MODELVIEW_MATRIX )
> print modelview
> glPopMatrix()
>
> but I am getting this:
> [[1.0, 0.0, 0.0, 0.0], [0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 1.0, 0.0],  
> [0.0, 0.0, 0.0, 1.0]]
> Which does,'t solve my problem.
>
>
> ----- Original Message ----
> From: Gary Herron <gh...@is...>
> Cc: pyo...@li...
> Sent: Tuesday, July 22, 2008 8:48:24 PM
> Subject: Re: [PyOpenGL-Users] get Translation inside matrix stack
>
> Shantytown Saxena wrote:
> >
> > glPushMatrix()
> > glTranslate(5,0,0)
> > glTranslate(10,0,0)
> > glTranslate(5,0,0)
> > # How do I get here total increment of x axis(which is 5+10+5=20)
> > before I Pop up.
> > glPopMatrix()
>
> All the transformations are recorded by OpenGL in a 4x4 matrix.
> You can recover that matrix like this:
>
>     buff = (ctypes.c_double*16)()
>     pyglet.gl.glGetDoublev(stack, buff)
>
> If you started with the identity and did no other transformations  
> you'll
> find the 20 in that 4x4 array.
>
> In either the [0,3] or [3,0] element.  (I've forgotten which way  
> Opengl
> stores the array now.)
>
> Gary Herron
>
>
> >
> >  
> ------------------------------------------------------------------------
> >
> >  
> -------------------------------------------------------------------------
> > This SF.Net email is sponsored by the Moblin Your Move Developer's  
> challenge
> > Build the coolest Linux based applications with Moblin SDK & win  
> great prizes
> > Grand prize is a trip for two to an Open Source event anywhere in  
> the world
> > http://moblin-contest.org/redirect.php?banner_id=100&url=/
> >  
> ------------------------------------------------------------------------
> >
> > _______________________________________________
> > PyOpenGL Homepage
> > http://pyopengl.sourceforge.net
> > _______________________________________________
> > PyOpenGL-Users mailing list
> > PyO...@li...
> > https://lists.sourceforge.net/lists/listinfo/pyopengl-users
> >
>
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's  
> challenge
> Build the coolest Linux based applications with Moblin SDK & win  
> great prizes
> Grand prize is a trip for two to an Open Source event anywhere in  
> the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> PyOpenGL Homepage
> http://pyopengl.sourceforge.net
> _______________________________________________
> PyOpenGL-Users mailing list
> PyO...@li...
> https://lists.sourceforge.net/lists/listinfo/pyopengl-users
>
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's  
> challenge
> Build the coolest Linux based applications with Moblin SDK & win  
> great prizes
> Grand prize is a trip for two to an Open Source event anywhere in  
> the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/_______________________________________________
> PyOpenGL Homepage
> http://pyopengl.sourceforge.net
> _______________________________________________
> PyOpenGL-Users mailing list
> PyO...@li...
> https://lists.sourceforge.net/lists/listinfo/pyopengl-users

Re: [PyOpenGL-Users] get Translation inside matrix stack

From: Gary H. <gh...@is...> - 2008-07-22 18:14:52

Prashant Saxena wrote:
> I am sorry but I didn't get any success with your code. I tried this:
>
> glPushMatrix()
> glTranslate(5,0,0)
> glTranslate(10,0,0)
> glTranslate(5,0,0)
> # To get total increment of x axis(which is 5+10+5=20)
> modelview = glGetFloatv( GL_MODELVIEW_MATRIX )
> print modelview
> glPopMatrix()

My mistake.   The glGetDouble/glGetFloat call is the right thing here, 
but I was confusing my Python-to-OpenGL libraries.  Your syntax is 
correct for PyOpenGL.  (Mine was for a library called Pyglet.)

>
> but I am getting this:
> [[1.0, 0.0, 0.0, 0.0], [0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 1.0, 0.0], 
> [0.0, 0.0, 0.0, 1.0]]
> Which does,'t solve my problem.

There are several matrix stacks maintained by OpenGL.  Which one are you 
using when you issue the glPushMatrix-glTranslate-glPopMatrix calls?   
Probably not the GL_MODELVIEW_MATRIX since that's still the identity 
when you get it back.   You need to choose your matrix first:
    glMatrixMode(GL_MODELVIEW)  # Specify which matrix
    then do your matrix ops
    ... = glGetFloatv( GL_MODELVIEW_MATRIX )  # Retrieve the matrix back

Gary Herron


>
> ----- Original Message ----
> From: Prashant Saxena <ani...@ya...>
> To: Gary Herron <gh...@is...>
> Sent: Tuesday, July 22, 2008 9:59:38 PM
> Subject: Re: [PyOpenGL-Users] get Translation inside matrix stack
>
> I am sorry but I didn't get any success with your code. I tried this:
>
> glPushMatrix()
> glTranslate(5,0,0)
> glTranslate(10,0,0)
> glTranslate(5,0,0)
> # To get total increment of x axis(which is 5+10+5=20)
> modelview = glGetFloatv( GL_MODELVIEW_MATRIX )
> print modelview
> glPopMatrix()
>
> but I am getting this:
> [[1.0, 0.0, 0.0, 0.0], [0.0, 1.0, 0.0, 0.0], [0.0, 0.0, 1.0, 0.0], 
> [0.0, 0.0, 0.0, 1.0]]
> Which does,'t solve my problem.
>
>
> ----- Original Message ----
> From: Gary Herron <gh...@is...>
> Cc: pyo...@li...
> Sent: Tuesday, July 22, 2008 8:48:24 PM
> Subject: Re: [PyOpenGL-Users] get Translation inside matrix stack
>
> Shantytown Saxena wrote:
> >
> > glPushMatrix()
> > glTranslate(5,0,0)
> > glTranslate(10,0,0)
> > glTranslate(5,0,0)
> > # How do I get here total increment of x axis(which is 5+10+5=20)
> > before I Pop up.
> > glPopMatrix()
>
> All the transformations are recorded by OpenGL in a 4x4 matrix.
> You can recover that matrix like this:
>
>     buff = (ctypes.c_double*16)()
>     pyglet.gl <http://pyglet.gl.gl>.glGetDoublev(stack, buff)
>
> If you started with the identity and did no other transformations you'll
> find the 20 in that 4x4 array.
>
> In either the [0,3] or [3,0] element.  (I've forgotten which way Opengl
> stores the array now.)
>
> Gary Herron
>
>
> >
> > ------------------------------------------------------------------------
> >
> > 
> -------------------------------------------------------------------------
> > This SF.Net email is sponsored by the Moblin Your Move Developer's 
> challenge
> > Build the coolest Linux based applications with Moblin SDK & win 
> great prizes
> > Grand prize is a trip for two to an Open Source event anywhere in 
> the world
> > http://moblin-contest.org/redirect.php?banner_id=100&url=/ 
> <http://moblin-contest.org/redirect.php?banner_id=100&url=/>
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > PyOpenGL Homepage
> > http://pyopengl.sourceforge.net
> > _______________________________________________
> > PyOpenGL-Users mailing list
> > PyO...@li... 
> <mailto:PyO...@li...>
> > https://lists.sourceforge.net/lists/listinfo/pyopengl-users
> > 
>
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's 
> challenge
> Build the coolest Linux based applications with Moblin SDK & win great 
> prizes
> Grand prize is a trip for two to an Open Source event anywhere in the 
> world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/ 
> <http://moblin-contest.org/redirect.php?banner_id=100&url=/>
> _______________________________________________
> PyOpenGL Homepage
> http://pyopengl.sourceforge.net
> _______________________________________________
> PyOpenGL-Users mailing list
> PyO...@li... 
> <mailto:PyO...@li...>
> https://lists.sourceforge.net/lists/listinfo/pyopengl-users
>
>
> ------------------------------------------------------------------------
>
> -------------------------------------------------------------------------
> This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
> Build the coolest Linux based applications with Moblin SDK & win great prizes
> Grand prize is a trip for two to an Open Source event anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> ------------------------------------------------------------------------
>
> _______________________________________________
> PyOpenGL Homepage
> http://pyopengl.sourceforge.net
> _______________________________________________
> PyOpenGL-Users mailing list
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> https://lists.sourceforge.net/lists/listinfo/pyopengl-users
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