pyopengl-users

[PyOpenGL-Users] Creating a postscript image of a scene : how do I use openglutil ?

[Champ H. <cha...@be...>]

Hello,

I need to create PostScript image of a scene created with PyOpenGL. I
have seen that "openglutil" should provide the required
functionnalities such as "openglutil.glSaveEPS('teapot.eps', 240,
240)". However my installation does not seem to recognize "openglutil"
and I get the error message : "NameError: global name 'openglutil' is
not defined" when I run the following program (lising #3 of article
http://www.linuxjournal.com/article.php?sid=4830):

from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.Tk import *
import sys

def display(togl):
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
   glColor3f(0.3, 1.0, 1.0)
   glMaterialfv(GL_FRONT, GL_AMBIENT,
   [0.1745, 0.0, 0.1, 0.0])
   glMaterialfv(GL_FRONT, GL_DIFFUSE,
   [0.1, 0.0, 0.6, 0.0])
   glMaterialfv(GL_FRONT, GL_SPECULAR,
   [0.7, 0.6, 0.8, 0.0])
   glMaterialf(GL_FRONT, GL_SHININESS, 80)
   glutSolidTeapot(1.0)
   glFlush()
   openglutil.glSaveEPS('teapot.eps', 240, 240)
   sys.exit()

togl = Opengl(width = 250, height = 250, double = 1)
togl.redraw  = display
togl.pack(side = 'top', expand = 1, fill = 'both')
togl.basic_lighting()
togl.set_background(0, 0, 0)
togl.mainloop()

Here is my system configuration:
- windows XP professional
- python 2.2.2
- PyOpenGL 2.0.0.44

What do I need to install openglutil ? How to do it ? Is there other
way of creating images (jpeg, bmp, png, gif ...) from PyOpenGL scenes ?

Thanks,

Bernard

Re: [PyOpenGL-Users] Creating a postscript image of a scene : how do I use openglutil ?

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

openglutil was a PyOpenGL 1.x-specific add-on module that was dropped 
for the 2.x series because the functionality could all be written in 
Python (this allowed us to eliminate the libpng and libjpeg dependencies 
of the 1.x series) and result in more flexible and robust code. You can 
see samples of saving images linked off the glReadPixels manual page here:

    
http://pyopengl.sourceforge.net/documentation/manual/glReadPixels.3G.html

AFAIK all of those save to png or jpeg, but PIL does (apparently) 
support writting EPS from an image, so it should work fine.

HTH,
Mike


Champ Hippy wrote:

>Hello,
>
>I need to create PostScript image of a scene created with PyOpenGL. I
>have seen that "openglutil" should provide the required
>functionnalities such as "openglutil.glSaveEPS('teapot.eps', 240,
>240)". However my installation does not seem to recognize "openglutil"
>and I get the error message : "NameError: global name 'openglutil' is
>not defined" when I run the following program (lising #3 of article
>http://www.linuxjournal.com/article.php?sid=4830):
>  
>
...

_______________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://members.rogers.com/mcfletch/

Re: [PyOpenGL-Users] Creating a postscript image of a scene : how do I use openglutil ?

[gabor <ga...@z1...>]

On Mon, 2003-05-19 at 18:41, Mike C. Fletcher wrote:
> You can=20
> see samples of saving images linked off the glReadPixels manual page here=
:
>=20
>    =20
> http://pyopengl.sourceforge.net/documentation/manual/glReadPixels.3G.html
>=20
> AFAIK all of those save to png or jpeg, but PIL does (apparently)=20
> support writting EPS from an image, so it should work fine.

i'm not sure if he wants the same as me,but:

when i wrote my master thesis ( i used pyopengl -)), i needed to make a
lot of screenshots.

and i  also wanted to be able to make eps screenshots. i mean
vector-based eps screenshots.
that means if there is a line on the screen i want it to be described as
a line in the eps file. not as a series of dots. i know that eps is able
to handle vectorial data.
reason:
when printing the master-thesis, all the screenshots look a little ugly,
because the resolution of the monitor is a lot smaller than the
resolution of the printer. with a vector-based image i wouldn't have
that problem.

hope this helps,
gabor

Re: [PyOpenGL-Users] Creating a postscript image of a scene : how do I use openglutil ?

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

gabor wrote:
...

>when i wrote my master thesis ( i used pyopengl -)), i needed to make a
>lot of screenshots.
>
>and i  also wanted to be able to make eps screenshots. i mean
>vector-based eps screenshots.
>
...
I assume you used glFeedbackBuffer (I'm interpreting your message to 
mean you did create such screenshots)?  Do you (or anyone) have any 
sample code you'd be willing to share?  Rendering an OpenGL scene to 
postscript commands seems like it would be a fairly doable thing, but I 
haven't any experience in the area.  I'd imagine with the basic 
mechanism in-place it would be just as easy (maybe easier) to go to a 
format such as SVG so that the result would be editable in Illustrator 
or CorelDraw.

BTW, the openglutils module was just storing a bitmap in the EPS file, 
it wasn't AFAIK trying to draw the scene with PS commands.

Enjoy all,
Mike

_______________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://members.rogers.com/mcfletch/

Re: [PyOpenGL-Users] Creating a postscript image of a scene : how do I use openglutil ?

[gabor <ga...@z1...>]

On Mon, 2003-05-19 at 19:16, Mike C. Fletcher wrote:
> gabor wrote:
> ...
> >
> ...
> I assume you used glFeedbackBuffer (I'm interpreting your message to=20
> mean you did create such screenshots)?  Do you (or anyone) have any=20
> sample code you'd be willing to share?  Rendering an OpenGL scene to=20

no, i didn't do anything sophisticated :)

i simply create screenshots with kde, and that's all :(


gabor

Re: [PyOpenGL-Users] Creating a postscript image of a scene : how do I use openglutil ?

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

If anyone's interested the GLP library is an (LGPL) C++ lib to do OpenGL 
-> postscript:

    http://www.easysw.com/~mike/opengl/index.html

it honestly doesn't seem particuarly complex, it uses the feedback 
buffer, and apparently does some culling of the results to eliminate 
massive overdraw. 

Similar-looking C lib for the same purpose (also LGPL):

    http://www.geuz.org/gl2ps/

apparently had a Python wrapper at some point in time, though it doesn't 
appear to be available any more (Toby?)  All in all this looks like the 
most mature of the solutions (for instance it appears able to deal with 
intersection polygons, though if I'm reading right it may generate 
striated results for smooth-shaded polygons.

There's another variant on the same approach here:

    http://192.48.159.181/developers/code/mjktips/Feedback.html

Enjoy,
Mike

gabor wrote:

>On Mon, 2003-05-19 at 19:16, Mike C. Fletcher wrote:
>  
>
>>gabor wrote:
>>...
>>    
>>
>>...
>>I assume you used glFeedbackBuffer (I'm interpreting your message to 
>>mean you did create such screenshots)?  Do you (or anyone) have any 
>>sample code you'd be willing to share?  Rendering an OpenGL scene to 
>>    
>>
>
>no, i didn't do anything sophisticated :)
>
>i simply create screenshots with kde, and that's all :(
>
>
>gabor
>  
>
_______________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://members.rogers.com/mcfletch/

[PyOpenGL-Users] Preliminary gl2ps wrapper for PyOpenGL

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

I've just built (and done some minimal testing of) a gl2ps wrapper for 
use with PyOpenGL.  Haven't tested anything save the two primary entry 
points, but they seem to work properly.  As a note, the mechanism works 
using view-space absolute coordinates w/out the benefit of the depth 
buffer, so if your background-drawing code plays tricks such as clearing 
the depth buffer after drawing (which OpenGLContext does), you can wind 
up with your scene behind the background's geometry.

Anyway, if people are interested enough, I'll post the source 
somewhere.  The wrapper script is basically just a slightly trimmed 
version of the gl2ps.h header with some minimal type-mapping.  I wound 
up renaming the gl2ps.c file to _gl2ps.c to get around an annoying error 
where the build system was creating two gl2ps.o files.  Other than that 
no noticable changes to the base package that I can recall.  Oh, and at 
the moment you need to define WIN32  explicitly to build.  Haven't 
figured out why that's necessary as of yet.

Here's the results from a simple VRML file (one normally intended to be 
drawn w/out textures):
    http://members.rogers.com/mcfletch/programming/test.eps

Anyway, if anyone's interested, I'll look at polishing/finishing the 
wrapper and releasing it.

Enjoy all,
Mike

Mike C. Fletcher wrote:
...

> Similar-looking C lib for the same purpose (also LGPL):
>
>    http://www.geuz.org/gl2ps/
>
> apparently had a Python wrapper at some point in time, though it 
> doesn't appear to be available any more (Toby?)  All in all this looks 
> like the most mature of the solutions (for instance it appears able to 
> deal with intersection polygons, though if I'm reading right it may 
> generate striated results for smooth-shaded polygons.

...

_______________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://members.rogers.com/mcfletch/