Re: screen capture?

[James W. W. <os...@jw...>]

On Nov 6, 2005, at 12:16 PM, Keith Wiley wrote:

> Why will glReadPixels be difficult to use if Quesa is just QD3D  
> which is just OpenGL anyway?

Well, first of all I have to quibble with "Quesa is just QD3D which  
is just OpenGL".  If you use the RayShade renderer in Quesa, then it  
is not using OpenGL.  But the built-in renderers do use OpenGL.

In order to make sure that the OpenGL context is set correctly, you  
need to do the glReadPixels in a rendering loop.  You could choose to  
do the glReadPixels at the end of a normal rendering loop, in which  
case maybe the only trick is to call glFlush before glReadPixels.

When I've used glReadPixels, I wanted to just capture what had last  
been rendered, rather than rendering again. To do that, I had to take  
steps to keep the image from being cleared at the start of the fake  
rendering loop, and to keep the buffer from being swapped at the end.

>   Are you saying the Quesa reimplementation of the equivalent of  
> glReadPixels hasn't been done yet?

I'm not sure what you mean by that.  The QD3D API never had an  
equivalent of glReadPixels.