Re: [PyOpenGL-Users] vertex/texture arrays

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

The format for the string versions of array functions is the same as for 
a C array.  That is, it's the internal format of the array (not how you 
would write it in a C program).  For instance, the point (1.0, 2.0, 3.0) 
would be represented as:

'\x00\x00\x00\x00\x00\x00\xf0?\x00\x00\x00\x00\x00\x00\x00@\x00\x00\x00\x00\x00\x00\x08@'
(with \x00 meaning a byte with the value (hexidecimal) 0, \x08 being a 
byte with character number 8, etceteras)

(I didn't figure that out on my own by the way, I used the struct 
module).  You _could_ convert your data to that format by using the 
struct module, but it's a lot of work to go through when the other 
functions will do the conversions for you.

So, how do you use those functions?  Well, here's an example:

'''Test of the glDrawArrays function'''

from OpenGLContext import testingcontext
BaseContext, MainFunction = testingcontext.getInteractive()
from OpenGL.GL import *
from Numeric import array
import string

data = [
	(0,0,0),
	(1,0,0),
	(1,1,0),
	(0,1,0),
]

class TestContext( BaseContext):
	def Render( self, mode = 0):
		BaseContext.Render( self, mode )
		glVertexPointerd( data )
		glNormalPointerf([ (0,0,1)]*4 )
		glEnableClientState(GL_VERTEX_ARRAY);
		glEnableClientState(GL_NORMAL_ARRAY);
		glDrawArrays(GL_QUADS, 0, len(data))

if __name__ == "__main__":
	MainFunction ( TestContext)

<plug>
That's taken from the OpenGLContext/tests directory (with a simpler set 
of data in your format substituted).  You can find a lot of sample code 
in the tests directory that gives you examples of how to accomplish 
common tasks.
</plug>

Hope that helps,
Mike



Frank Raiser wrote:

> On Sun, Jan 06, 2002 at 11:13:24AM -0600, Tarn Weisner Burton wrote:
> 
>>All the PyOpenGL functions are documented in merged man pages at
>>http://pyopengl.sourceforge.net/documentation/manual/
>>
>>Although the only the prototypes for the decorated functions
>>(glVertexPointerf, etc.) are given in the man pages, they are described
>>in more detail in the user's manual.  This documentation is also
>>distributed with 2.0, with the exception of the merged man pages which
>>will be included in the next version.
>>
> 
> I've checked these but couldn't really get anything new from it.
> 
> 
>>In short, glVertexPointer is like the C function in that it takes a
>>Python string and it respects the stride arguments (in the future it may
>>use the buffer protocol also), whereas glVertexPointerf uses a Python
>>array (or Numeric) and doesn't need stride arguments.
>>
> 
> How exactly does the string have to look like?
> I tried having a list vertices = [] and calling vertices.extend([x,y,z])
> for each vertex, then did a repr(vertices)[1:-1].replace(',','') to get
> a string of successive "x1 y1 z1 x2 y2 z2.." vertices, but that didn't
> work at all with glVertexPointer.
> 
> 
>>Sorry, haven't figured out the INVALID_OPERATION problem yet.
>>
> 
> :( This is giving me a headache as I just can't get any more info out. I
> don't know what to check, why it is invalid.. nothing.
> 
> Thanks for your help,
> 


-- 
_______________________________________
   Mike C. Fletcher
   http://members.rogers.com/mcfletch/