Path: chuka.playstation.co.uk!scea!peter_alau@playstation.sony.com
From: Craig Venz <craig@cobite.com>
Newsgroups: scee.yaroze.programming.2d_graphics
Subject: Re: Transparent screen grabs?
Date: Wed, 21 Oct 1998 09:55:03 -0400
Organization: SCEA News Server
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References: <362B0900.27655A77@bristol.ac.uk> <362DD8C8.3290@manc.u-net.com>
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James Shaughnessy wrote:
> 
> Yes indeed a good question there.  You say you've tried setting all
> the STP bits for each frame -- but are you setting them while
> on the frame buffer?  This will take in the order of 100,000 HSyncs
> if you are using a LoadImage and a StoreImage for each pixel by my
> reckoning, so as you say causes a rediculous slow-down.
> 
> Have you tried StoreImage'ing the whole screen to main memory,
> then doing some speedy bit-masking to all the pixels, then a quick
> LoadImage back to VRAM where the sprite info is?  The code could be:
> 
>   RECT screen = {0, activeBuff*240, 320, 240};
>   u_long *mainmem = (u_long *)RESERVED_MEM_ADDR; // or use malloc()
> 
>   StoreImage(&screen, &mainmem);
>   for (i=0; i<320*240/2; i++;)
>     mainmem[i] |= (1<<15) + (1<<31);
>   LoadImage(&screen_sprite_area, &mainmem);
> 
> Note how TWO pixel STP bits are set for each loop execution, so
> it only (?) needs to loop about 40,000 times.  It's only doing one
> logical OR (as 1<<15 + 1<<31 is evaluated at compile time) so it
> should be plenty quick enough and do the trick if no other bright
> soul comes up with a better solution.
> Later,
> Jim
> 
> TEJ Madams wrote:
> > Hi there,
> >          I've been programming the Yaroze for a couple of weeks with
> > a small amount of sucess but I've come across a problem. I wanted to
> > recreate that 'fade to battle' effect in FFVII and I know how it's
> > done but I don't know exactly how to do it. I need to grab the screen
> > and make it into a transparent sprite an paste the image back onto
> > the screen again after modifying a bit. Now here's my point, to make
> > a TIM image transparent, the transparency bits for every pixel in the
> > image need to be set but when you grab the screen, these bits aren't
> > set. Arse. All the bits in the screen grab (320*240) need to be set
> > every frame which slows the frame rate down dramatically. I know it
> > can be done quicker but how?

I had an idea for doing this myself, by setting 2 GsSPRITE structures to
point to the previous doublebuffer, as 16bit sprites... I would think
that would be a real easy way to do it...

While trying this out, though, I've had no luck getting it to work,
whatsoever. I think I must be doing something wrong with GetTPage and
the u and v values... <shrug>

Anyway, I still maintain that this _should_ work. Anyone want to prove
me wrong?

Craig