bobp@amiga.UUCP (Robert S. Pariseau) (11/24/85)
TITLE: Demo Wars! Our honor has been sullied! (grin!) Atari has finally gotten around to duplicating our bouncing ball! You know, of course.....This Means War! The famous Amiga Bouncing Ball demo was written a little under 2 years ago. It was written in C code in the span of about 1 week. That time included producing and refining the "crash" sound effects that come out *>IN STEREO<* while the ball is bouncing (eat your hearts out Atari)! As I think most people are aware, the Bouncing Ball rotates via "color cycle animation". Each of the red and white patches is actually made up of 7 strips. 14 of the 32 Amiga color registers are assigned one per strip, repeating in sets of 14 along each row of the ball. The ball appears to rotate because we assign 7 strips to white and 7 strips to red and then cycle the colors through those 14 color registers. No Blitting is involved. The ball bounces due to changing the pointers which tell the video DMA where to get the image out of memory. We change the ball and shadow bit-planes, but not the grid bit-plane, so the ball appears to move with respect to the grid while the grid stays stationary on your monitor. Again, no blitting, sprites, etc., are involved. We did it this way because, way back then, we didn't HAVE any blitter hardware that worked in the mocked-up Amigas. Of course the ball is visually (and aurally!) appealing, but what I think it really shows is JUST HOW EASY it is to produce such "special effects" in the Amiga. Frankly we've been amazed that Atari couldn't duplicate it sooner. [Oh yes, as an aside, the ball also exists on the Commodore C-64 in a form suitable for the resolution of the C-64.] Much has been made of the fact that the Atari ball rotates faster than the Amiga ball. As I think you can perceive from the above discussion, rotating the ball fast is *>EASY<*. You can make the ball rotate *>BLINDINGLY<* fast just by cycling the color registers faster. (How fast can YOU change 14 memory locations with a 68000?) One of the cute things with the Amiga ball is that it can rotate as *>SLOWLY<* as it does and still appear smooth. We can do this because we can afford to dedicate 14 color registers just to the ball rotation. Well now that Atari has fired the opening salvo, I think we'll just return a little fire. Anyone who seriously thinks the ST can stand up against the Amiga in a battle of graphics and sound has rocks in their head! Let's see now....a few sprites here....a little Hold and Modify over there.....maybe some hardware assisted area fills and line draws.... FM modulated stereo sound built in (It's SO cumbersome having to carry that synthesizer around to pretend your ST can actually produce music, isn't it Jack)....dual playfield ops with transparency.... any number of screen interrupts anywhere in the screen....perhaps a few blits to do *>REAL<* animation (yeah, guys, Robo-City is about a year and a half old, too)....and just a tad of multitasking.... This is going to be FUN! You got balls Atari? You're going to need them! Meanwhile, guys, if you think anyone is BELIEVING this nonsense, just type LeftAmiga-N to pop the Workbench to the foreground, drag it down so people can still see the bouncing ball running, and do a little multi-tasking. (Large grin!)