Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!esosun!net1!sdcsvax!sdcc6!sdcc7!ee162faq
From: ee162faq@sdcc7.ucsd.EDU (JOHN SCHULTZ)
Newsgroups: comp.sys.amiga
Subject: Re: Blitter	(general discussion of double buffering techniques)
Message-ID: <833@sdcc7.ucsd.EDU>
Date: Sat, 6-Dec-86 01:59:41 EST
Article-I.D.: sdcc7.833
Posted: Sat Dec  6 01:59:41 1986
Date-Received: Sun, 7-Dec-86 03:29:39 EST
References: <8612041959.AA22053@cory.Berkeley.EDU>
Reply-To: ee162faq@sdcc7.ucsd.edu.UUCP (JOHN SCHULTZ)
Organization: U.C. San Diego, Academic Computer Center
Lines: 43

Currently I am just doing one blit per image (shape) update.  So,
you are saying that it would be faster to set the MASK variable to
allow only certain planes to be affected (copied to), say 2 bitplane
blits as opposed to 4? (obviously twice as fast).  Yet you must also
set up the colors in the shapes so the blit will look correct (?).
Currently, the simulation runs so fast that I had to slow down the
relative velocities of the jets (but slows down quite a bit in higher
levels when many items are being processed).  Using the techniques mentioned,
would the user be able to notice any increase in performance?

Yeah, I'm not using ClipRect.  Neat things happen when the blitter is
lead astray... (like permanently losing the display [nothing, black]
until rebooting (had a 1 pixel bug in my clip routine, and that's
all it takes).

All of my shapes were drawn using "dpaint lo 4" and loaded into their
respective bitmaps.  The colormap for the Viewport is obtained from the
last shape read in, and converted from RGB into colortable entries.
So, what would be neccessary to try "Method 2" given the above
scenario?  Draw, for example, the US Jet in only colors 1-7, and the
Libyan Jet in 8-15?  Or does it require tedious (simple?) bit-bit
calculations and spurious color usage?

I've tried using Forbid to speed up processing but the narrator runs
as a seperate task...  (could Permit before a call...)
I've noticed a few benchmarks posted; does Forbid speed up a given
task significantly?

Finally, define "customize"... I haven't studied OwnBlitter, can I
just call OwnBlitter when the simulation starts, then DisownBlitter
when done?  

Just looked it up. More to it than that.  Is the trouble (code time)
worth the extra effort?  If you think the RKM is short on examples,
(that actually work) you won't believe the spartan examples supplied with m2
documentation (none are supplied showing lower level function, like
blitter manipulation, etc).  Guess I came out ahead, though, because
now transfering from C to m2 is fairly simple.

Thanks again for your support.

John
7OHN