Subject: Re: [stella] Polar to Cartesian Co-Ordinate Converter From: "Roger Williams" <mer02@xxxxxxxxxxxxx> Date: Mon, 22 Oct 2001 16:21:49 -0700 |
> Especially the fast division may open some new opportunites. To bad, that I can't use them for my new demo, since I need the remainder too > You don't know a formula for this, do you? No, that's a hard one with the 6502 set. The log trick works because I accept the rounding errors, which are big enough to make it unacceptable for some functions -- for example, you couldn't use it to do base conversion because there are a lot of +-1 errors even close in. But for drawing a display which can be approximate, it does the job. The cartesian to polar conversion is even less accurate than the polar to cartesian, but that's not as important because it's mainly used for back conversions and the errors aren't as "visible" the way I'm using it. > I guess, the rounding error could be further reduced by using 16 bit value tables (for LOG only of course :-) Correct? Yes, the larger the log table the more accurate the results will be (but they will never be quite perfect). Remember a full 16-bit log table would be 64K, but you could get a lot of midrange improvement (+-1 pixel at 128, for example) with a log table 3 or 4 pages long. But this would give you ALL the overhead of 16-bit math in the conversion. (Going to 1/1024 circle angular resolution is also trivial with a 256-byte trig table, but again you get 16-bit angles.) In this version I was going for sheer blazing speed. --Roger Williams - Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
Re: [stella] Polar to Cartesian Co-, Chris Wilkson | Thread | Re: [stella] Polar to Cartesian Co-, Glenn Saunders |
Re: [stella] Polar to Cartesian Co-, Roger Williams | Date | [stella] Homebrew Idea: Super Mosca, Len Charest |
Month |