pyopengl-users — Discussion of all PyOpenGL matters.

[PyOpenGL-Users] Attempt to retrieve context when no valid context

[Mads I. <mp...@co...>]

Hi,

I am running an app in an PyQt QGLWidget. If the window is minimized, and
the method for rendering the object that should be displayed is called, I
get the error 'OpenGL.error.Error: Attempt to retrieve context when no
valid context' (included below), when glColorPointerd() is called.

Is there:

* a way to check whether a valid context is set?
* force the context to be set?

Best regards,

Mads

glColorPointerd(colors)
  File
"/home/mpi/svn/quantumconnect/external-libs/build/lib/python2.6/site-packages/OpenGL/wrapper.py",
line 410, in wrapperCall
    cArgs,
  File
"/home/mpi/svn/quantumconnect/external-libs/build/lib/python2.6/site-packages/OpenGL/arrays/arrayhelpers.py",
line 66, in __call__
    contextdata.setValue( self.constant, pyArgs[self.pointerIndex] )
  File
"/home/mpi/svn/quantumconnect/external-libs/build/lib/python2.6/site-packages/OpenGL/contextdata.py",
line 49, in setValue
    context = getContext( context )
  File
"/home/mpi/svn/quantumconnect/external-libs/build/lib/python2.6/site-packages/OpenGL/contextdata.py",
line 32, in getContext
    """Attempt to retrieve context when no valid context"""
OpenGL.error.Error: Attempt to retrieve context when no valid context

Re: [PyOpenGL-Users] Checking Shader Errors

[Gijs <in...@bs...>]

Ian Mallett wrote:
> The driver is: 8.552.0.0 (10/28/08). 
> I have gl_FragData[/n/] just for MRT purposes.  Good to know about
> these issues though.  Why /is/ it an issue?  Just to be annoying?
>
> Ian
My guess it is a bug in the driver since other drivers have no issues
with it at all (that I know of). And it wouldn't make sense either, to
restrict the programmer to only use const integers to index
language-specific arrays.

Gijs

Re: [PyOpenGL-Users] Checking Shader Errors

[Ian M. <geo...@gm...>]

The driver is: 8.552.0.0 (10/28/08).
I have gl_FragData[*n*] just for MRT purposes.  Good to know about these
issues though.  Why *is* it an issue?  Just to be annoying?

Ian

Re: [PyOpenGL-Users] Checking Shader Errors

[Gijs <in...@bs...>]

Ian Mallett wrote:
> Yes, this was basically what I came up with.
>
> The problem turns out to be that for gl_LightSource[n], n must be a
> literal int or const int.  I'm not sure why this could be.  Ideas?  
>
> I solved the problem by passing the light source itself to the function.  
>
> There's a few more other problems, but it's mostly done.
>
> Ian
I have run into a similar problem regarding indexes of arrays like
these. I tried to index gl_FragColor using a variable. Something which
the Mac OS X driver doesn't like at all. So I unrolled the for-loop and
used const integers instead of variables. However, I only saw this
problem when I was using my mac. In Windows and Linux it worked like a
charm, both using the ATI 9.3 drivers. In Linux the 9.2 driver actually
crashed when I used arrays like this. So I don't really know what your
problem is, but it could be driver or videocard related. See if updating
your drivers fixes any problems.

Regards, Gijs

Re: [PyOpenGL-Users] Checking Shader Errors

[Ian M. <geo...@gm...>]

Yes, this was basically what I came up with.
The problem turns out to be that for gl_LightSource[n], n must be a literal
int or const int.  I'm not sure why this could be.  Ideas?

I solved the problem by passing the light source itself to the function.

There's a few more other problems, but it's mostly done.

Ian

Re: [PyOpenGL-Users] PyOpenGL accelerator module

[Mike C. F. <mcf...@vr...>]

Eric Jonas wrote:
> Hello! First my apologies if this has been discussed on the list
> recently, I couldn't find the relevant sf page for searching the mailing
> list archives. 
>   
Don't think we've ever discussed it on-list.
> I'm interested in constructing an openGL-based time series viewer for
> some of our tens-of-megabyte time series data, that will work
> interactively from python. Matplotlib totally fails when looking at data
> of this scale, and the speed of navigation is pretty crucial. 
>
> But I'd like to do as much as possible from python/numpy/scipy, and then
> pass the loosly-processed data off to the GPU (i've done a bit of GLSL
> work) for visualization. My only concern is that, with its new
> ctypes-based bindings, pyopengl3 will be too slow for this sort of
> application. 
>   
Actually, that's the use-case where the ctypes bindings tend to be 
irrelevant.  There is a per-array overhead in the bindings to get the 
data-pointer out of the array, but once the data-pointer is retrieved 
it's basically just passing the value directly in to OpenGL.  If you're 
processing huge data-arrays you're likely not going to notice the 
overhead of the data-pointer retrieval, as it will be swamped in the 
real work getting done.
> ...Which brings me to the accelerator module -- do people think this
> would really be necessary for this sort of app? How much work would it
> be to prototype things with the existing pyopengl3 interface and then
> "drop in" the accelerator module? I've not been able to find much
> documentation about the shape of the eventual module. 
>   
It's intended to be an entirely transparent accelerator module.  The 
core code already has hooks for most of the accelerator modules, so it 
will attempt to import from OpenGL_accelerate the various functions that 
are available.  The basic code is already in the bzr/source packages 
with a script called setupaccel.py which builds the package.  Mostly the 
intent is just to extend and debug it to eliminate significant 
hotspots.  Usage will just be to install the accelerator module, no 
changes to code should be necessary.

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com

[PyOpenGL-Users] PyOpenGL accelerator module

[Eric J. <jo...@MI...>]

Hello! First my apologies if this has been discussed on the list
recently, I couldn't find the relevant sf page for searching the mailing
list archives. 

I'm interested in constructing an openGL-based time series viewer for
some of our tens-of-megabyte time series data, that will work
interactively from python. Matplotlib totally fails when looking at data
of this scale, and the speed of navigation is pretty crucial. 

But I'd like to do as much as possible from python/numpy/scipy, and then
pass the loosly-processed data off to the GPU (i've done a bit of GLSL
work) for visualization. My only concern is that, with its new
ctypes-based bindings, pyopengl3 will be too slow for this sort of
application. 

...Which brings me to the accelerator module -- do people think this
would really be necessary for this sort of app? How much work would it
be to prototype things with the existing pyopengl3 interface and then
"drop in" the accelerator module? I've not been able to find much
documentation about the shape of the eventual module. 

Thanks again, I'm excited to get back to hacking OpenGL !
			...Eric

Re: [PyOpenGL-Users] Shader Function Problems

[Ian M. <geo...@gm...>]

Yea, normal is custom defined.

I'm working on a fix which works, I think.  The problem was with sending
variable ints to gl_LightSource[n].

Re: [PyOpenGL-Users] Shader Function Problems

[Mike C. F. <mcf...@vr...>]

Ian Mallett wrote:
...
> But strangely, glGetInfoLogARB(...) spits out:
>
>
>
> Fragment shader(s) failed to link,  vertex shader(s) linked. 
> Fragment Shader not supported by HW
>
> Needless to say, it crashes later on glUseProgramObjectARB(...) with an 'invalid operation'.
Yeah, saw the same with my ATI Radeon 3650, I wound up using both 
glGetInfoLog and glGetProgramInfoLog and found that with both I'd 
normally get some description of a failure, but that the shaders would 
pass validation (i.e. the first programmatic indication of the error was 
on the invalid operation error).  For OpenGLContext's shader support I 
wound up doing a try:except around the glUseProgram call and if there's 
a GL error raised I print all of the logs for all of the linked 
components as well as the program's logs.
>   These problems occur when certain functions are called in my program.  Here's a function that causes such an error:
>
>
>   
> float diffuse_coefficient(int lightnum) {
>     vec3 l = normalize(gl_LightSource[lightnum].position.xyz-vVertex);
>     return max(dot(normal,l),0.0);
> }
>
> My ideas:
> vVertex is a varying vec3.  Could this be the problem?
Doesn't look like a problem to me, I seem to recall using varying 
vectors in such ways many times.
> is max(dot(normal,l),0.0) too much for one line?  I saw something 
> about ALU limits.  I don't know if this qualifies. 
I'd be surprised if that went over any limit, I've certainly written 
more complex calculations.

Sorry I don't have more help to offer here.  Might want to check that 
lightnum is the proper value?  Also, stupid question, where'd you get 
"normal" there?  I don't see it in my handy GLSL quickref.  Is it from 
some outer scope (or an attribute/uniform)?

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com

Re: [PyOpenGL-Users] Checking Shader Errors

[Gijs <in...@bs...>]

Ian Mallett wrote:
> Hi,
>
> I've got a great shader library, and it's nearly done.  Unfortunately,
> certain custom functions have problems on ATI cards.  I'm trying to
> add error reporting to get useful errors about it.  Unfortunately,
> glGetShaderInfoLog() seems to fail.  It works for me, with NVidia. 
>
> This function:
>
> def CompileShader(source,shaderType):
>     shader = glCreateShaderObjectARB(shaderType)
>     glShaderSourceARB(shader,[source])
>     glCompileShaderARB(shader)
>     return shader
>
> provides the "shader" that is passed as the argument to
> glGetShaderInfoLog().  I have no idea what's wrong, and I really need
> to have error reporting to debug this. 
>
> Curiously, glGetInfoLogARB() seems to work fine, but it does not give
> useful errors (fragment shader failed to compile successfully before
> linking or some such).  I tried using ctypes in ways like here
> <http://www.pygame.org/wiki/GLSLExample?parent=CookBook> or here
> <http://www.pygame.org/wiki/GLSL_ARB_Example?parent=CookBook>, but
> they don't work for either of us.
>
> I need errors.  Help.
>
> Thanks,
> Ian

Hey Ian,

I made some error reporting code for my own stuff a while back. Maybe
you can use some of it to see what is going wrong with your code.

Regards,
Gijs


def compileShader(source, shader_type, shader_name):
  shader = glCreateShaderObjectARB(shader_type)
  glShaderSourceARB(shader, source)
  glCompileShaderARB(shader)

  status = glGetObjectParameterivARB(shader, GL_COMPILE_STATUS)
  if not status:
    printShaderLog(shader, shader_name)
    glDeleteObjectARB(shader)
    raise ValueError, 'Shader compilation failed'

  return shader


def compileProgram(vertex_source, fragment_source, shader_name):
  vertex_shader   = None
  fragment_shader = None
  program         = glCreateProgramObjectARB()

  if (type(vertex_source) == str):
    vertex_source = [vertex_source]
  if (type(fragment_source) == str):
    fragment_source = [fragment_source]

  if vertex_source:
    vertex_shader = compileShader(vertex_source, GL_VERTEX_SHADER,
shader_name)
    glAttachObjectARB(program, vertex_shader)
  if fragment_source:
    fragment_shader = compileShader(fragment_source, GL_FRAGMENT_SHADER,
shader_name)
    glAttachObjectARB(program, fragment_shader)

  glLinkProgramARB(program)
  status = glGetObjectParameterivARB(program, GL_OBJECT_LINK_STATUS_ARB)
  if not status:
    print >> sys.stderr, glGetInfoLogARB(program)
    raise ValueError, 'Failed to link shader ('+str(shader_name)+')'

  glValidateProgramARB(program)
  status = glGetObjectParameterivARB(program, GL_OBJECT_VALIDATE_STATUS_ARB)
  if not status:
    print >> sys.stderr, glGetInfoLogARB(program)
    raise ValueError, 'Failed to validate shader ('+str(shader_name)+')'

  if vertex_shader:
    glDeleteObjectARB(vertex_shader)
  if fragment_shader:
    glDeleteObjectARB(fragment_shader)

  if glGetObjectParameterivARB(program, GL_INFO_LOG_LENGTH) > 0:
    print ("Info log for shader '" + str(shader_name) + "':\n" +
glGetInfoLogARB(program))

  return program


def printShaderLog(shader, shader_name):
  if glGetObjectParameterivARB(shader, GL_INFO_LOG_LENGTH) > 0:
    log = glGetInfoLogARB(shader)
    print >> sys.stderr, "Problem with shader '" + shader_name + "'"
    print >> sys.stderr, log
  else:
    print >> sys.stderr, "Problem with shader '" + shader_name + "', but
no log is available"

[PyOpenGL-Users] Shader Function Problems

[Ian M. <geo...@gm...>]

Hi,

I finally got some sort of error checking working for ATI cards.  The errors
are weird.  glGetShaderInfoLog(...) for each part of the program spits out:

Vertex shader was successfully compiled to run on hardware.
Fragment shader was successfully compiled to run on hardware.

But strangely, glGetInfoLogARB(...) spits out:

Fragment shader(s) failed to link,  vertex shader(s) linked.
Fragment Shader not supported by HW

Needless to say, it crashes later on glUseProgramObjectARB(...) with
an 'invalid operation'.  These problems occur when certain functions
are called in my program.  Here's a function that causes such an
error:

float diffuse_coefficient(int lightnum) {
    vec3 l = normalize(gl_LightSource[lightnum].position.xyz-vVertex);
    return max(dot(normal,l),0.0);
}

My ideas:
vVertex is a varying vec3.  Could this be the problem?
is max(dot(normal,l),0.0) too much for one line?  I saw something about ALU
limits.  I don't know if this qualifies.

Any other ideas?  What's going on here?  How can I make this work?

Ian

[PyOpenGL-Users] Checking Shader Errors

[Ian M. <geo...@gm...>]

Hi,

I've got a great shader library, and it's nearly done.  Unfortunately,
certain custom functions have problems on ATI cards.  I'm trying to add
error reporting to get useful errors about it.  Unfortunately,
glGetShaderInfoLog() seems to fail.  It works for me, with NVidia.

This function:

def CompileShader(source,shaderType):
    shader = glCreateShaderObjectARB(shaderType)
    glShaderSourceARB(shader,[source])
    glCompileShaderARB(shader)
    return shader

provides the "shader" that is passed as the argument to glGetShaderInfoLog().
I have no idea what's wrong, and I really need to have error reporting to
debug this.

Curiously, glGetInfoLogARB() seems to work fine, but it does not give useful
errors (fragment shader failed to compile successfully before linking or
some such).  I tried using ctypes in ways like
here<http://www.pygame.org/wiki/GLSLExample?parent=CookBook>or
here <http://www.pygame.org/wiki/GLSL_ARB_Example?parent=CookBook>, but they
don't work for either of us.

I need errors.  Help.

Thanks,
Ian

Re: [PyOpenGL-Users] font-rendering problem

[Mike C. F. <mcf...@vr...>]

vwf wrote:
> Hello Python-OpenGL Experts,
>
> I keep having problems with a part of my program. This program once worked,
> but stopped working after an upgrade of my system.
>
> Can someone help me get it running again? The problem appears in the initialisation 
> phase of the program, during the "prerendering" of the fonts.
>
> Thank you,
> Frits
>   
Hi Frits,

This is a known error fixed in current BZR head, if you need the fix 
immediately you'll need to check out the bzr trunk.  Out of curiosity, 
*what* is value at that point?  AFAIK everything is *supposed* to have a 
__class__ attribute, but obviously *something* doesn't.

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com

[PyOpenGL-Users] font-rendering problem

[vwf <vw...@vu...>]

Hello Python-OpenGL Experts,

I keep having problems with a part of my program. This program once worked,
but stopped working after an upgrade of my system.

Can someone help me get it running again? The problem appears in the initialisation 
phase of the program, during the "prerendering" of the fonts.

Thank you,
Frits



mine:~/fppu/manavnew$ ./manav_01.py
Traceback (most recent call last):
  File "./manav_01.py", line 22, in <module>
    from networking import *
  File "/home/frits/fppu/manavnew/networking.py", line 17, in <module>
    from constant_manav import state,scen
  File "/home/frits/fppu/manavnew/constant_manav.py", line 119, in <module>
    class cfont:
  File "/home/frits/fppu/manavnew/constant_manav.py", line 123, in cfont
    l1.build('0123456789.')
  File "/home/frits/fppu/manavnew/pyfont.py", line 97, in build
    l=self.font.getChar(c)
  File "/home/frits/fppu/manavnew/pyfont.py", line 127, in getChar
    current = self.createChar(char)
  File "/home/frits/fppu/manavnew/pyfont.py", line 150, in createChar
    list = self.textureToList( dataArray, metrics )
  File "/home/frits/fppu/manavnew/pyfont.py", line 188, in textureToList
    raise
  File "/home/frits/fppu/manavnew/pyfont.py", line 183, in textureToList
    glDrawPixelsub( mode, array )
  File "/var/lib/python-support/python2.5/OpenGL/wrapper.py", line 1273, in __call__
    return self.finalise()( *args, **named )
  File "/var/lib/python-support/python2.5/OpenGL/wrapper.py", line 469, in wrapperCall
    pyArgs = tuple( calculate_pyArgs( args ))
  File "/var/lib/python-support/python2.5/OpenGL/wrapper.py", line 328, in calculate_pyArgs
    yield converter(args[index], self, args)
  File "/var/lib/python-support/python2.5/OpenGL/GL/images.py", line 422, in __call__
    return self.arrayType.asArray( arg )
  File "/var/lib/python-support/python2.5/OpenGL/arrays/arraydatatype.py", line 55, in asArray
    return cls.getHandler(value).asArray( value, typeCode or cls.typeConstant )
  File "/var/lib/python-support/python2.5/OpenGL/arrays/arraydatatype.py", line 25, in getHandler
    return cls.getHandler( value )
  File "/var/lib/python-support/python2.5/OpenGL/arrays/formathandler.py", line 16, in __call__
    typ = value.__class__
AttributeError: ('__class__', <OpenGL.GL.images.TypedImageInputConverter object at 0xba1150c>)


The offending code:

# Adapted from:
# OpenGLContext 2.0.0b2
#
# OpenGLContext License:
#
# Copyright (c) 2000-2003, Michael C. Fletcher and Contributors
# All rights reserved.
[...]

    def textureToList( self, array, metrics):
        # Compile Numeric Python array to a display-list
        # use a single texture and coordinates for texmap version        
        # special case ' ' so that it's not rendered as an image

        mode = GL_LUMINANCE_ALPHA
        list = glGenLists (1)
        glNewList( list, GL_COMPILE )
        try:
            try:
                if metrics.char != ' ':
                    glDrawPixelsub( mode, array )
                    glBitmap( 0,0,0,0, metrics.width,0, None )
                    #glDisable( GL_BLEND)
            except Exception:
                glDeleteLists( list, 1 )
                raise
        finally:
            glEndList()
        return list


All on Debian Lenny (stable/5.0)
python:
  Installed: 2.5.2-3
python-opengl:
  Installed: 3.0.0~c1-0

Re: [PyOpenGL-Users] A big problem with glOrtho

[projetmbc <pro...@cl...>]

Thanks a lot.

Christophe.



Dirk Reiners a écrit :
>
>     Hi Christophe,
>
> projetmbc wrote:
>>
>> Where there are mathematic ( from the OpenGL's point of view) 
>> definitions of the different perspectives ?
>
> you can get the actual matrices from the manpages 
> (http://www.opengl.org/sdk/docs/man) or from the Redbook 
> (http://www.opengl.org/documentation/red_book, Appendix F), which is a 
> good resource to have when you're doing OpenGL anyway.
>
> Yours
>
>     Dirk

Re: [PyOpenGL-Users] A big problem with glOrtho

[Dirk R. <dir...@gm...>]

	Hi Christophe,

projetmbc wrote:
> 
> Where there are mathematic ( from the OpenGL's point of view) 
> definitions of the different perspectives ?

you can get the actual matrices from the manpages 
(http://www.opengl.org/sdk/docs/man) or from the Redbook 
(http://www.opengl.org/documentation/red_book, Appendix F), which is a good 
resource to have when you're doing OpenGL anyway.

Yours

	Dirk

Re: [PyOpenGL-Users] A big problem with glOrtho

[projetmbc <pro...@cl...>]

Thanks for the information. Finally the problem was another  :-[  :
                GL.glEnable(GL.GL_CULL_FACE)

Where there are mathematic ( from the OpenGL's point of view) 
definitions of the different perspectives ?

Best regards and a great thanks for the help.
Christophe.


> Definitely recommend using a perspective matrix for your first OpenGL 
> programs.  I use this class for perspective:
>
> class glLibView3D():
>     def __init__(self,rect,angle,near=0.1,far=1000.0):
>         self.rect = list(rect)
>         self.angle = angle
>         self.near = near
>         self.far = far
>     def set_angle(self,value):
>         self.angle = angle
>     def set_near(self,value):
>         self.near = value
>     def set_far(self,value):
>         self.far = value
>     def set_view(self):
>         glViewport(*self.rect)
>         glMatrixMode(GL_PROJECTION)
>         glLoadIdentity()
>         
> gluPerspective(self.angle,float(self.rect[2])/float(self.rect[3]),\
>         self.near,self.far)
>         glMatrixMode(GL_MODELVIEW)
>         glLoadIdentity()
>
> HTH,
> Ian

Re: [PyOpenGL-Users] A big problem with glOrtho

[Ian M. <geo...@gm...>]

Definitely recommend using a perspective matrix for your first OpenGL
programs.  I use this class for perspective:

class glLibView3D():
    def __init__(self,rect,angle,near=0.1,far=1000.0):
        self.rect = list(rect)
        self.angle = angle
        self.near = near
        self.far = far
    def set_angle(self,value):
        self.angle = angle
    def set_near(self,value):
        self.near = value
    def set_far(self,value):
        self.far = value
    def set_view(self):
        glViewport(*self.rect)
        glMatrixMode(GL_PROJECTION)
        glLoadIdentity()
        gluPerspective(self.angle,float(self.rect[2])/float(self.rect[3]),\
        self.near,self.far)
        glMatrixMode(GL_MODELVIEW)
        glLoadIdentity()

HTH,
Ian

[PyOpenGL-Users] A big problem with glOrtho

[projetmbc <pro...@cl...>]

I'm becoming crazy with the definition of the two last parameters of glOrtho.

My problem is that I would like to a box  with for example XMin=-12, XMax=12, YMin=-12, YMax=12 and ZMin=-5, ZMax=5. I do not understand how to do that simple thing such as nothing in the cube could disapear when manipulating with the mouse.

My problem is not how to draw the box but to define a view such as all the box will be always entirely visible.

Christophe.

Re: [PyOpenGL-Users] Missing Quadrilaters in a view-Newbie's question

[projetmbc <pro...@cl...>]

Mike C. Fletcher a écrit :
> projetmbc wrote:
>> Hello,
>> this is my first post on this list. I've decided to use OpenGL with 
>> PyQt. My first test is to draw a cartesian surface using quadrilaters.
>> My problem is that when I move my scene with the mouse, sometime the 
>> point of view makes disappear some quadrilaters. I think that is due 
>> to my lake of knowledge about the definition of the view scene. How 
>> can I avoid this kind of problem ?
>>   
> I'm guessing what you're seeing is the near clipping plane, which 
> would "cut" your quadrilaterals if they were to pass it.  You can set 
> the near clipping plane to a reasonably small value, but if you "walk 
> through" your geometry then the geometry is going to get clipped.
>
> HTH,
> Mike
>
Thanks, I finally decide to read OpenGL Programming Guide. Then I will 
be back here with "real" problems.  ;-)

Christophe.

Re: [PyOpenGL-Users] Missing Quadrilaters in a view-Newbie's question

[Mike C. F. <mcf...@vr...>]

projetmbc wrote:
> Hello,
> this is my first post on this list. I've decided to use OpenGL with 
> PyQt. My first test is to draw a cartesian surface using quadrilaters.
> My problem is that when I move my scene with the mouse, sometime the 
> point of view makes disappear some quadrilaters. I think that is due to 
> my lake of knowledge about the definition of the view scene. How can I 
> avoid this kind of problem ?
>   
I'm guessing what you're seeing is the near clipping plane, which would 
"cut" your quadrilaterals if they were to pass it.  You can set the near 
clipping plane to a reasonably small value, but if you "walk through" 
your geometry then the geometry is going to get clipped.

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com

Re: [PyOpenGL-Users] GLUError and gluNurbsCurve

[Ivo U. <iv...@iu...>]

Mike C. Fletcher wrote:
> Hmm, are you saying those ints are supposed to be returned as values
> from gluNurbsCurve?  My manual says that it is supposed to have a void
> return type.  Or is this supposed to show up in a glGetError return
> value?  Basically I'm wondering whether these are supposed to be part of
> GLU or part of the wrapper?  If they are part of GLU I don't yet know
> how to retrieve them.

sorry for not responding earlier Mike
(but better ever than never :D)

No! gluNurbsCurve does not return int (it returns void).
I've tracked error through (sgi) source and it goes like this:
1) *gluNurbsCurve* calls *nurbscurve* on GLUnurbs object
2) *nurbscurve* method creates knotvector object and
calls *do_check_knots* function on that object
3) *do_check_knots* calls *knotvector::validate* method
(which is the one I sent you) and puts the result
in the status variable. If there is any error (status!=0)
*do_nurbserror(status)* is called
4) *do_nurbs_error* calls *errorHandler*
5) *errorHandler* calls *postError* with appropriate GluError

after this I'm not sure what comes next :(

> 
> For now, I've added them to the wrapper and have them controlled by
> OpenGL.ERROR_CHECKING, so you can turn them off when your code is no
> longer producing invalid values and want to reclaim the performance. 
> You should be able to check out current head via:
> 
>    bzr branch lp:pyopengl
> 
> and check that the code now catches your errors.
> 
> Thanks for the bug report,
> Mike
> 

Ok. I'll test it this weekend

have fun,
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[PyOpenGL-Users] Missing Quadrilaters in a view-Newbie's question

[projetmbc <pro...@cl...>]

Hello,
this is my first post on this list. I've decided to use OpenGL with 
PyQt. My first test is to draw a cartesian surface using quadrilaters.
My problem is that when I move my scene with the mouse, sometime the 
point of view makes disappear some quadrilaters. I think that is due to 
my lake of knowledge about the definition of the view scene. How can I 
avoid this kind of problem ?

Best regards.
Christophe

PS : I could put herer my python code if it's necessary.

Re: [PyOpenGL-Users] Exception on Exit

[Ian M. <geo...@gm...>]

Thanks.

The problem was that __del__() tried to call an OpenGL function (to disable
the light).  Going "del Light1" before exiting fixed the problem.

Re: [PyOpenGL-Users] Exception on Exit

[Mike C. F. <mcf...@vr...>]

Ian Mallett wrote:
> Hi,
>
> I have code that creates an exception on exit.  I can't imagine why. 
>
> Exception exceptions.TypeError: "'NoneType' object is not callable" in 
> <bound method glLibLight.__del__ of <glLib.glLibLight.glLibLight 
> instance at 0x034B3F80>> ignored
>
> This error only happens on exit.  Ideas?
I'm gathering "glLib.glLibLight" is your code.  You'll have a __del__ 
method on one of those objects that tries to call e.g. an OpenGL 
function.  During interpreter shutdown the global namespaces of modules 
are cleared out so that every name is set to None.  Your __del__ method 
is trying to call a function by name and the result is an attempt to 
call the None object.  If you need to have access to a function in a 
__del__ method you need to arrange to be sure that function is available 
(e.g. by binding as an argument) or check that it is non-null before 
calling it, or catch the error in the __del__.

Incidentally, it is generally better to use weakrefs rather than __del__ 
methods, as __del__ methods prevent garbage collection from operating if 
there is a loop in your object references.  See the vbo module for an 
example of usage, though as I read it I realize that it's not properly 
handling cases where the namespace is cleared out before it's called 
either.  (Should catch the errors to make it safe).

HTH,
Mike

-- 
________________________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://www.vrplumber.com
  http://blog.vrplumber.com