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Old 27 January 2012, 13:52   #26
Mrs Beanbag
Glastonbridge Software
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Join Date: Jan 2012
Location: Edinburgh/Scotland
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Originally Posted by Codetapper View Post
The starfield in the demo moves so fast that you could probably fake the whole thing with about 10 frames of animation in a loop (and even mirror the top and bottom half) and perhaps plot the odd big circle star to make it appear that it's not an anim.

Like a number of people on here, I don't see the big deal about this intro either. An A500 could easily do a very similar version without too much hassle.
I think a real starfield is possible using the blitter. The blitter can plot a lot of points in a frame by clever use of line mode. Just make the starfield out of lines of up to 16 stars instead of individual stars, it probably wouldn't be noticed. Use 1-pixel per scanline mode but set the modulo so that they all come out on the same line, put a random value in BLTBDAT... if you can do 50 stars in a frame you can do 500.

The sinewave scroller is trivial. I've googled to see what other people's technique is, everyone seems to suggest blitting the vertical columns one at a time, thus a 16-pixel wide section needs 16 blits. It can be done in four. Yes and still retain 1-pixel resolution. It's only blitting one bitplane each frame, the other bitplanes are just previous versions through which it cycles, making a trail effect.

The copper effects can be done by changing the palette every 20 pixels easily, use a single bitplane with a dithering pattern on it, and blit pre-rendered lines into the copperlist. The copperlist is in Chip Ram right, you can blit into it.
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