Subject: Re: [stella] Sprites - Questions to games programmers From: Thomas Jentzsch <tjentzsch@xxxxxx> Date: Sat, 8 May 2004 16:30:08 +0200 |
Christian Bogey wrote: > I looked carefully at some vcs games pictures and it > seems that the sprite resolution suggest the graphics > are updated every 2 scanlines. > I'am wrong ? Not at all, many games update the sprite every 2nd scanline. > If I'm not, I'd like to know if it's a common practice? Is the > reason is to reserve some cycles to make extra things ? Yup, it just depends on how much time you need inside your kernel for other stuff. > Usually, what are you doing in your own games (are you updating the > sprites datas every 1, 2 or more scanlines ?). Thrust has a two scanline resolution for the sprites, Jammed, Cave1K and Splattform 2600 have single scanline resolution. > What is your advice about that to write an effective kernal ? Hm, hard to tell. First you should understand as much as possible of the 2600 hardware and its limitations. Then usually the first step is to think about the playfield graphics. Do you need them and do they have to be asymmetrical? Do you have to draw them every scanline? Do you need all three PF registers (often PF0 is not used). How much RAM will you need for drawing the PF? Then you can calculate how much time is left and how often you can update the sprites. This is the point where you should decide after how many scanlines the kernel will repeat. Also important: Do you have to reposition the sprites inside the kernel? Think about using VDEL which IMO makes the kernel code much more flexible, allowing more complex kernels. Now use the remaining cycles for missiles or color changes etc. Depending on how much time is left here, there are multiple ways to utilize those free cycles. Instead of making an universal kernel for the whole screen, sometimes it's better to use different specialized kernel for horizontal stripes of the screen. Pitfall is a good example of this. At any of those steps you will quite often go back to the previous points, change your decision and restart the iteration again. Have fun! Thomas _______________________________________________________ Thomas Jentzsch | *** Every bit is sacred ! *** tjentzsch at web dot de | ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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