Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!ukc!harrier.ukc.ac.uk!gos.ukc.ac.uk!dac From: dac@ukc.ac.uk (David Clear) Newsgroups: comp.sys.atari.st Subject: Re: Fine scrollin' Keywords: graphics atari helpx2 Message-ID: <2827@gos.ukc.ac.uk> Date: 21 Feb 90 22:46:05 GMT References: <1199@elmgate.UUCP> <590@spcc386.UUCP> <4474@brahma.cs.hw.ac.uk> Reply-To: dac@ukc.ac.uk (David Clear) Organization: Computing Lab, University of Kent at Canterbury, UK. Lines: 47 In article <4474@brahma.cs.hw.ac.uk> neil@cs.hw.ac.uk (Neil Forsyth) writes: [about sync scrolling] > >I ran a DEMO that does this on an STE and the video hardware really chucked >up on it. The custom chips on the STE no longer have the same quirks as the >old ones so if you don't want to lose compatibilty don't do it. Also the >sync scrolling technique uses frequency toggling and I believe loses on >a native 60Hz display. I ran "The Cuddly Demo" on a STE and, sure enough, the sync scrolling died. Its use shouldn't be ruled out though. It is the fastest way to do high speed scrolling on a ST. If you're planning on writing a fast scrolling game on a STE using its hardware support then, if the design is portable, it may be worth writing a dual version with two screen handlers for the two STs. As far as I know most games run in 50Hz anyway as this gives the code 1/50th of a second per update rather than 1/60th (obvious). So you get more time per frame using 50Hz. If you can't run every frame then every other frame at 60Hz looks smoother than every other frame at 50Hz (my scroll code forces a 50Hz screen - I haven't tried to make it run on a 60Hz screen and I'm not sure that it's possible). The code I posted last night to do sync scrolling was very fragile timing-wise and I suggested using two timers to make everything solid. Well, in the light of day I realised that the HBL can be used to sync at the top of the screen (and a nop is 4 cycles, not 8 as I said). Anyway, using the HBL can make the whole thing very solid. Maybe you've noticed, I really am trying to plug sync scrolling. I haven't the time to write anything commercial but I really do like high speed shoot-em-ups and believe that fast, every frame update is a must. Sooner or later such games will appear for the STE and older STs will be left standing. Fast scrolling CAN be done on a ST. You have the code. Read it, understand it, re-write it and use it. Games for the ST will never have the sound quality of the STE, or the BLiTTER speed, or the specialised video chip functions, but it's gameplay that really counts and fast scrolling is it. Dave. PS. I always wanted LucasFilm to do "Rescue On Fractalus" for the ST... Hey! What ever happened to "Defender"? A *real* version (with original(ish) graphics)? -- % cc life.c | David Clear % a.out | Computer Science, University of Kent, Segmentation fault (core dumped) | Canterbury, England.