Cedric's sdl engine email/patch has been hijacked into
a bitter battle over evas and opengl :)
Simon wrote:
> It would indeed make the engine generic but then, if the engine
> swaps the buffers by itself, the Evas couldn't be integrated in
> an OpenGL application: here is how we could embed an Evas in an
> OpenGL app, if the engine wasn't swapping the buffers:
>
> 1. Creation of a drawable
> 2. Creation of a GL-context from the drawable
> 3. Creation of the GL-engine
> 3. While (1)
> {
> game->scene->render();
> evas->engine->render();
> game->overlay->render();
> swap_buffers(GL-context);
> }
>
> Now, if the engine swaps the buffers at the end of the rendering
> process (which is currently the case), the overlay can't be rendered
> anymore (or you'll have to put the overlay->render() call in the
> swap_buffers() callback, but it's kind of tricky imho)
Ok, this assumes that the game->render() itself is rendering
to the gl front/back buffer and that it too doesn't flush things.
But if that's the case, then why can't the evas gl engine in question
be rendering to a pbuffer or texture say, and then draw that to the
main render buffer (eg. as a textured quad), and then flush things?
No matter how much you want to put evas canvases into a
gl based rendering context, you are also going to want to do the
opposite - use gl rendering in an evas gl canvas.
The cleanest way to do these kinds of things, wether it's
gl based or xrender based or cairo based or your-software-routines
or via some 3D-game-engine (or even, egods, a raytracer!), is to
have evas engine specific buffers to draw to.
This is why the software engines are so powerful/versatile,
it provides a full circle - you can draw to a display target via
the software engines, and you can draw to a software buffer target,
and you can set such a buffer as 'data' for image objects.
This kind of completeness would be very desirable as well,
at least withing the context of engines driven by a given rendering
backend - software, xrender, gl, cairo, ...
jose.
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