Re: [PyOpenGL-Users] 2D (Re: Bitmaps and Circles?)

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

sn...@so... wrote:
...

> perfectly). Now the last portion of the engine - for the initial 
> release, at
> least - is the whole graphic shpiel.
> PyGame is very nice, I hope I'm not offending anyone - but it is, in my
> experience, a bit slow. OpenGL is fast (the demos seemed promising, I 
> wrote
> a few quick programs and liked the resulting fps), and I figured I 
> wouldn't
> mind going through some hoops to get OpenGL's speed into an oo-2d 
> oriented
> interface.

Oh, then, go for it, but keep in mind that you're dealing with a system 
that thinks in terms of points, lines and triangles, so you're going to 
have to do your own tessellating (though there are some tools that will 
help with that, such as GLU).

gluDisk gives you a simple filled circle if you set the inner radius to 0
setting gluQuadricDrawStyle to GLU_SILHOUETTE will give you empty 
circles (no fill) with gluDisk.  You could also just use the sin and cos 
ufuncs from Numeric to generate coordinates and draw them using either 
an array-drawing call or a display list:

        a = arange(0.0,2*math.pi,.02)
        xes = sin(a)
        yes = cos(a)
        coords = zeros( (len(xes),3),'d')
        coords[:,0] = xes
        coords[:,1] = yes

(the .02 there says to use .02 radians as the sampling rate, or around 
1.1 degrees).

As for drawing bitmaps, there's an ARB extension ARB.window_pos which 
gives simple positioning for bitmaps.  There's also simple glDrawPixels 
(normally pretty slow) and loading a bitmap into a texture and 
displaying it on a properly-proportioned rectangle aligned with the 
screen (fast, and basically the "right" way to do it (IMO)).

You might want to take a look at PyUI for sample code showing how to do 
this kind of stuff. IIRC it is using lots of simple orthogonal display 
of bitmaps, complex shapes (windows, text, etceteras) and is game-targeted.

HTH,
Mike

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