Subject: Re: Aw: Re: [stella] Maze Craze and 650x From: Erik Mooney <erik@xxxxxxxxxx> Date: Tue, 21 Aug 2001 11:36:00 -0400 |
8/21/2001 5:53:37 AM, cybergoth@xxxxxxxx wrote: >NOW we'd have enough RAM to display 6 balls with Bob's >multiplexing algorythms, so we could have 6 >almost_non_flickering Balls displayed using only one object. > >...but then all the repositioning needed within the >multiplexer killed the idea again before I finished typing it... This brings to mind an idea I've had for a while but haven't actually tried implementing. Is it possible to use a multiple-branching kernel via an indirect jump to time RESPx writes without having to use an entire scanline to position an object? What I mean is something like this. Offscreen, you do some calculation and store into SpritePosition (value 0 to 10) and HmoveValue. You have a table set up in ROM for BranchTable (values for the addresses for the Kernel# labels). Then you do this during the kernel: LDY SpritePosition LDA BranchTable,Y STA KernelBranch JMP (KernelBranch) Kernel0 STA RESP0 do other processing like six playfield writes LDA HmoveValue STA HMP0 JMP EndLine Kernel1 do playfield write #1 STA RESP0 do playfield writes 2-6 LDA HmoveValue STA HMP0 JMP EndLine Kernel2 do playfield writes #1-2 STA RESP0 do playfield writes #3-6 LDA HmoveValue STA HMP0 JMP EndLine [etc] Kernel10 do playfield writes #1-6 LDA HmoveValue STA HMP0 STA RESP0 EndLine STA WSYNC STA HMOVE The Kernel# labels vary the position of the STA RESP0 by equal to or less than 15 pixels between them, so you can use HMOVE to get the object to any position on the screen. So you've positioned your object by using lots and lots of ROM, but only 28 cycles all told (including the last HMOVE). Much less than using a full 76 cycle scanline. Is this feasible? Has it already been done anywhere? - Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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