[GRASS-dev] nviz python thoughts

[William Kyngesburye]

On Dec 21, 2008, at 12:14 PM, Glynn Clements wrote:

>> ... Some sample code from Apple - it's about using surface textures,
>> but the window parts could be useful:
>
> Using OpenGL in a window should be taken care of by wxGLCanvas. It's
> getting off-screen contexts which we (probably) have to do ourselves.
>
> The situation is the same with the existing nviz; Togl provides a
> canvas on which OpenGL can be used. The only glX/wgl/agl functions
> outside of Togl are the code in do_zoom.c to get an off-screen context
> for saving output to files.
>
I guess I'm missing something here.  I understand about the offscreen  
part, so where does the window come in in render.c?  Is it a hidden  
window, just so we can get the context?


>> Looks like mac_win is just a placeholder here.  For now, comment this
>> line and have Nviz_make_current_render_window return 0 for  
>> OPENGL_AQUA?
>
> In that case, just:
>
>     /* TODO: mac_win */
> -    aglMakeCurrent((AGLDrawable) mac_win, rwin->contextId);
> +    aglMakeCurrent((AGLDrawable) 0, rwin->contextId);
>
> should get it to compile (which is all we're after for now).


Should it return 0, just to be nice?  presumably, nviz_cmd would fail  
gracefully if the render.c functions return a failure, but would it do  
so on success but with a nonexistent context?


Anyways, the online API docs that we found way back when to get the  
function names seems to have been wrong.  Strangely, render.c compiles  
with the wrong names, but doesn't link:

Undefined symbols:
   "_aglChoosePixelFmt", referenced from:
       _Nviz_create_render_window in render.o
   "_aglCreateAGLPixmap", referenced from:
       _Nviz_create_render_window in render.o
   "_aglMakeCurrent", referenced from:
       _Nviz_make_current_render_window in render.o
   "_aglDestroyAGLPixmap", referenced from:
       _Nviz_destroy_render_window in render.o

Indeed, these are not in the AGL headers.  What I can find is:

extern AGLPixelFormat aglChoosePixelFormat(const AGLDevice *gdevs,  
GLint ndev, const GLint *attribs);

extern GLboolean aglSetCurrentContext(AGLContext ctx);
(I didn't see any form of "make current", with a context AND display/ 
window parameters)

There don't appear to be any pixmap functions, but there are pbuffer  
functions.

Looks like nviz.h has the right names for types in the render_window  
struct.


PS. render.h is not included by render.c, or anything else in GRASS.   
It looks like everything in render.h is in nviz.h.  Maybe render.h  
should be deleted? (it was confusing me with it's duplicated  
render_window declaration)

-----
William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
http://www.kyngchaos.com/

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