Subject: Re: [stella] Real 3D Space Calculations From: "Yvo Zoer" <yzoer@xxxxxxxxx> Date: Mon, 27 Aug 2001 12:38:02 0700 
Hi! I think I missed most of this thread but I've done some 3d stuff on the gameboy after reading an article from Steven Judd ( he of fridge fame :) Using a table of squares ( 256 bytes for the table ) you can rotate any point in the range 64 +63 with 2 subtractions an add and 2 lookups, which is pretty neat. What's more, with a second table you can project that same point using the same method and get the divide for free. All in all pretty neat. If anyone's interested gimme a shout or check out www.ffd2.com Cheers, Yvo  Original Message  From: "Ronald Gershwin" <wazzapfool@xxxxxxxxx> To: <stella@xxxxxxxxxxx> Sent: Monday, August 27, 2001 9:07 AM Subject: Re: [stella] Real 3D Space Calculations > That solution would work good if you just wanted to > rotate. Converting the polar coordinates to 2d > coordintes would be a snap too, because you could just > say 'ok, left side of the screen corresponds to 45 > degrees horizontal, middle is 0, and right is +45 > degrees' or whatever (Might cause a little distortion > around the edges, but should be ok). But it's kind of > like robbing Peter to pay Paul, because then you'd > have to do a lot of trigonometry to do any linear > *movement* in the 3d world... > > Ben L. > aka Ronald Gershwin :) > >  Chris Wilkson <ecwilkso@xxxxxxx> wrote: > > I'm surprised that no one has mention spherical > > coordinates yet. > > > > For those who don't know, these consist of 2 angles > > (theta and phi) > > and a radius (r). They are all referenced to the > > center of the sphere. > > One way to implement it is to have theta and phi > > range from 0 to 180 > > degrees (or 90 to +90) and have r range from x to > > +x, where x is the > > maximum distance. > > > > An example: Moving your head. If you spin your > > head left to right, > > theta measures the angle from the center. Looking > > straight ahead is > > zero. If you nod your head up and down, phi > > measures that angle. > > Again, looking straight ahead is zero. This gives > > you vision of the > > hemisphere in front of you. Going on with the > > example...r measures > > the distance from the center of your head. Positive > > r is in front of > > you, negative r is behind you. > > > > Now, when your ship rotates, all you have to do is > > add angles...not > > multiply. Of course at some point, you need to > > convert to screen > > coordinates, but this can be done using sine and > > cosine lookup tables.... > > > > Chris > > > > On Fri, 24 Aug 2001, Glenn Saunders wrote: > > > > > << > > > Even this would be hard, though. For one, it > > involves > > > multiplication and division of nonpowerof2 > > numbers, > > > and values that won't fit in 8 bits...and that's > > just > > > the beginning... > > > >> > > > > > > Really the best approach is to disassemble Star > > Raiders for the 400/800. > > > It's only 8K. SR has more accurate pseudo3D > > coordinate system than any > > > 8bit space sim I know of outside of Elite, and > > Elite (as I remember it on > > > the Apple II at least) had a really sluggish > > framerate so I don't think that > > > would be a good game to copy. > > > > > > You could also look at the disassembly of Solaris. > > Even though it's behind > > > the ship perspective, it's still kinda 3D with the > > radar and all. > > > > > > > > > > > > > > > _________________________________________________________________ > > > Get your FREE download of MSN Explorer at > > http://explorer.msn.com/intl.asp > > > > > > > > >  > > > Archives (includes files) at > > http://www.biglist.com/lists/stella/archives/ > > > Unsub & more at > > http://www.biglist.com/lists/stella/ > > > > > > > > >  > > Archives (includes files) at > > http://www.biglist.com/lists/stella/archives/ > > Unsub & more at http://www.biglist.com/lists/stella/ > > > __________________________________________________ > Do You Yahoo!? > Make international calls for as low as $.04/minute with Yahoo! Messenger > http://phonecard.yahoo.com/ > >  > Archives (includes files) at http://www.biglist.com/lists/stella/archives/ > Unsub & more at http://www.biglist.com/lists/stella/  Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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