[SDL] blitting with SDL/OpenGL

[Jan Pfeifer]

so far i haven't had problems working simultaneously with non-ortho and ortho 
(with screen coordinates for pixmaps) modelview/projection matrices. But i 
haven't done "select rendering yet" nor do i know how to find out what screen 
area has been redrawn by my 3d models (the program has to recopy from the 
background only the "dirtied" area). (did i understand you right?)

but then, my main problem still is to find out the best way to copy the 
surfaces (images) around (from memory to video memory, and from video memory 
to video memory) using SDL/OpenGL ...

any ideas ?

thanks :-)

jan

On Monday 04 November 2002 15:34, Atrix Wolfe wrote:
> gl can also work in orthographic mode.  Ortho is 2d blitting basicly and
> lets you work in screen space instead of 3d.  You cant specify draw this
> from (50,50)-(590,430) in pixel points but you could do something like map
> your view matrix in such a way to make the screens dimensions go from 0-100
> and then by drawing a rectangle from (25,25)-(75,75) it would make a
> rectangle in the middle of the screen that is 50% of the width and height.
> The only problems i have had with combining ortho and non-ortho gl is in
> rendering in select mode (where you load names and draw things and it tells
> you what was drawn under the mouse cursor).  It doesnt seem to like doing
> that from both modes but ::shrug:: i might not be doing it right.
>
>
> ----- Original Message -----
> From: "Jan Pfeifer" <janpf at yahoo-inc.com>
> To: "SDL" <sdl at libsdl.org>
> Sent: Monday, November 04, 2002 9:00 AM
> Subject: [SDL] blitting with SDL/OpenGL
>
> > hi :-)
> >
> > i'm looking for a fast (and still portable) way for blitting in
> > SDL+OpenGL
>
> in
>
> > 2 scenarios, but I'm not being able to find out how to do this. Any hints
>
> ?
>
> > I'll be grateful for any comments.
> >
> > Scenario 1)
> > Fixed Image (background for the 3d animation):
> > the ways i wonder it's possible to do this is:
> >
> > a) create a big texture with the background and draw a texturized quad
> > wherever region i want to redraw. How should one handle when the size of
>
> the
>
> > screen is not easily divided into 2^n sized rectangules ? (for instance
> > 800x600) Do i have to handle the assossiated geometry complexity or is
>
> there
>
> > some library ?
> >
> > b) create an auxiliary color buffer, glDrawPixels the image there and
> > then glCopyPixels the are for redraw. I've heard (read actually) that
> > this is
>
> slow
>
> > (because it allows lots of optional per pixel processing, even though i'm
>
> not
>
> > using any). And i didn't find anything in SDL to create the auxiliary
>
> buffer
>
> > ... (I wonder GLX -- or equivalent -- has to handle this).
> >
> >
> >
> > Scenario 2)
> > Animated image, coming from main memory every frame. Again, i thought of
>
> two
>
> > simillar aproaches:
> >
> > a) use glDrawPixels: i found out this to be terrible slow :( ... even in
>
> the
>
> > default (no special per pixel processing) settings ... i would guess that
> > this would be hw accelerated for any board that supports openGl but
> > apparently it's not ...
> >
> > b) use Texture: load each image to texture and paint the texturized quad
> >
> > any others ?
> >
> >
> >
> > again, thanks for any help/idea
> >
> > =)
> >
> > jan
> >
> > ps.: i'm new in the list so sorry if this has been discussed before
> > (searching i found out some discussion in 1999 only)
> >
> >
> > _______________________________________________
> > SDL mailing list
> > SDL at libsdl.org
> > http://www.libsdl.org/mailman/listinfo/sdl
>
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