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Amiga rotozoomer - Brian the Lion

category: general [glöplog]
 
I read in some forums that Amiga could do better Mode 7 than SNES. I was curious about this, because I have seen so many uses in SNES games that Amiga would struggle doing. And based on the best rotozoomers I had seen even in demos (lowres, not all bitplanes always) I thought it can't be. Usually the demos are doing the state of the art we hardly see in games.

So, I had this game in my Amiga CD32. At 9:30 there is both cylindrical mapping and in front another rotozoomer background with very good detail and colors. Something SNES can't do (only has one mode 7 layer) unless with SuperFX I guess.

https://www.youtube.com/watch?v=m-IDcTW8JQ4&feature=youtu.be&t=9m30s

But I thought it's because it's Amiga 1200. But now I try the game in Amiga500 emulator and it still runs.

The coder says '....by the way of the Nintendo (SNES), you can rotate round in increments of 1 degree, so you can rotate through 360 positions.with our system you can rotate through 512 to 1024 (degrees), which looks smoother.It's also a much cleaner rotation than the SNES.If you randomly pick an angle, and do same on SNES, it'll look much cleaner on the Amiga-the ones on the Nintendo are broken apart and there are bits hanging off......Rotation takes any size block from 16X16 to full screen and rotates it through 1024 degrees, which is about 3X more than anything SNES can do'

Also, my final question is, how did he do it? Some people say the Blitter, some say the Cooper. But the cooper is the chip that you can programm to do things per line, like change colors or other? Shouldn't it be the blitter? But how would you do such good rotozoomer with the blitter? I thought it's usually used for plain zooming, and those X-rotated cubes, by blitting prerendered bitmap lines scaled? And since I never saw such good rotozoomer in A500 demos, it made me wonder.

I still don't think SNES is worse than Amiga than this, ok maybe less angles and that, but it's much easier in SNES to have your game make smooth fullscreen fullcolor rotozoomer, it's common in the chip, not needed to do the most crazy magic ever.

But how did he do it? And why I haven't seen such quality rotozoomers in demos? Usually it's the demos doing impossible things that you don't see in games.
added on the 2015-01-09 15:02:28 by Optimus Optimus
added on the 2015-01-09 15:06:31 by hollowman hollowman
Quote:
And why I haven't seen such quality rotozoomers in demos? Usually it's the demos doing impossible things that you don't see in games.


Coder of the Brain the Lion zoomer: Kreator/Anarchy.
added on the 2015-01-09 15:20:02 by StingRay StingRay
Why call it a rotozoomer when it's only rotating and not zooming?
(There's a zoomer in the intro but that seems to just be the classic scrollreg-zoomer popularized by Chaos, which obviously isn't rotating)
Hmmok, on second look it might be zooming just a little bit. :D
Quote:
Usually the demos are doing the state of the art we hardly see in games.


Well.. I can't really remember as good, if any, vectors on Amiga demos when Jez San made them in his games :)
added on the 2015-01-09 15:43:57 by Serpent Serpent
Ok, I read it and sort of get it. Dual skew in both axes, one with hw scroll per line(?) and vertical with blitter. There is much more terminology I don't understand, but it's fine for me, I get the raw idea. But if you skew a lot, you still can't get much angle before looking bad. So, maybe also many prerendered angles of the same bitmap? (The platform in the video is fine, because little rotation angle, but there is a fully rotating big logo in the beginning of the game. And some more).

World of Commodore might have this version of rotozoomer, not the chunky one in the beginning but later. It moves slowly, you see some weird distortion of sizes, I bet it's similar technique though.
added on the 2015-01-09 15:52:01 by Optimus Optimus

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