Path: utzoo!utgpu!water!watmath!clyde!att-cb!osu-cis!tut.cis.ohio-state.edu!mailrus!umix!uunet!mcvax!enea!tut!santra!jmunkki From: jmunkki@santra.UUCP (Juri Munkki) Newsgroups: comp.sys.mac.programmer Subject: Re: screen swapping Message-ID: <12013@santra.UUCP> Date: 15 Apr 88 17:16:12 GMT References: Reply-To: jmunkki@santra.UUCP (Juri Munkki) Organization: Helsinki University of Technology, Finland Lines: 43 Someone once wrote: (: >> don't do it ... mac II stuff, etc. etc. etc... use off screen buffers >> and copy it onto the screen, etc. Right! In article bm1q+@andrew.cmu.edu (Benjamin Jameson McCurtain) writes: >NO NO NO NO!!!! I could care less about Mac II's right now, all I want to >do is REALLY FAST animation of a bunch of objects and even screen scrolling! No, no, no... You can have both. You have to write a few lines of code twice, but I think it's worth the trouble. Suppose that one day we'll have a really fast graphics coprocessor on the Mac. Now suppose that because it requires a large amount of the graphics memory bus bandwidth, the processor has an access time of (say) 3000 ns. You shouldn't even try to do animation using the main processor, if memory access is that slow. The coprocessor will probably then do the copybits several times faster than you can do it with a 680x0. What should you do? Read on... >Dark Castle (and beyond DC) both use screen swapping ( you can see the >effect by having the Jclock init while the screen is scrolling in the >labyrinths, it's all over the place)... Does these games work on a Mac II? Dark Castle and Beyond DC are different. BDC does things almost right, while DC doesn't work on a Mac II. If BDC detects that it is running on a Mac II, it uses copybits. You can even turn color on and watch the screen update a few times per minute! What BDC fails to do is give the user a choice. A vanilla BDC does not work on an Atari (just an example, I couldn't care less). There should be a check box in the settings dialog. The use could always try enabling "quick and dirty graphics", if his/her machine supported it. If you're interested in seeing source code for both ways of animation, read my August 1987 article in MacTutor (in J|rg's Forth Column). It has two separate programs...a single program might have been better. The other one works on a Mac II (I have a Mac II). The other program requires the old double buffered Mac screen. Juri Munkki jmunkki@santra.hut.fi jmunkki@fingate.bitnet