From: Jon M. Taylor <taylorj@gaia.ecs.csus.edu>
  To  : ggi-develop@eskimo.com
  Date: Fri, 28 May 1999 17:22:25 -0700 (PDT)

Re: Transparent Blit

On Fri, 28 May 1999, Thad Phetteplace wrote:

> > 
> > 	Why do you want to concern yourself with the hardware accelerated
> > part?  If you are writing to the LibGGI2D API, your only concern should be
> > whether the API supports transparents blits The target code determines
> > whether the transparent blit is accelerated or not.  It looks like
> > ggi2dBlitOp and ggi2dStretchBlitOp() are what you are looking for, but they
> > appear to be unimplemented as of yet.
> 
> I only mentioned hardware acceleration to avoid being sent a software
> only workaround (too slow for what I am doing).  If the groundwork is
> in place in LibGGI2D to do direct manipulation of video memory, I might
> take a shot at implementing ggi2dBlitOp.  
> A direct video mem copy with
> with some bit masking would probably be fast enough for my purposes,
> and it will give us some fallback code for when full accel is not
> available.
> 
> Is this type of blit a standard part of SVGA?  

	No.  Most newer cards support the Win32 ROP256 system, but some 
older cards do ROP16 and older systems like the Amiga only do ROP8.

> Or will we have to
> implement it on a card-by-card basis.  

	Yes.  I can help with a hardware implementation and some API work 
if you want to do the software implementation.  I need to do a LibGGI2D 
target for Savage4-KGI anyway at some point.

> As you can tell, I am not
> a low-level graphics expert, so any advice is appreciated.  I have
> a Diablo style game engine that I am trying to port to Linux and
> make open-source, and this blit issue is the final hurdle.
> 
> Thanks for the info!

	No problem.

Jon

---
'Cloning and the reprogramming of DNA is the first serious step in 
becoming one with God.'
	- Scientist G. Richard Seed