TomW wrote:
Re EORed sprites - why EOR them? Just have a blank column or two of pixels round each balloon and just STA them onto the screen.
Ouch
You are absolutely right, this is better again, though without a sprite plotting routine that trims for the screen edge you end up with unused 'border' pixels.MartinB wrote:
I can't just visualise how that technique would be applied to allow the balloon to both move one-pixel and waggle it's tail?
Yes, it's hard to wrap your brain about. I use another computer with a paint style app to plot one sprite EOR over the other (blast, brain freeze again in the last message, XOR - what did I mean by that!). Save the resultant mess as the new sprite. It's surprising what simple results are produced.
Again, using the space invader reference, the classic jellyfish top row... and sorry for the binary tables in this font
000110000..........000101000................000110000
001111000..........001000100................001111000
011111100..........010000010................011111100
110110110..EOR...101101101..results in...110110110
111111110..........100000001................111111110
001001000..........000010010................010110100
010110100..........000110101................100000010
101001010..........100001000................010000100
and another plot of the EOR sprite with further pixel offset to the right restores the original shape, the tentacles wave merrily on the breeze. I would expect even with the waving tail on your colour balloons the results will be the same, but your sprite would be described with strange colour nybble combinations
(This example combo will not work for left travel, you need another EOR sprite.)I suspect TomW is right, this idea is too much work when a simpler overplot will do, I regret suggesting it as the more I ponder it for your task I see it's going to gobble extra memory storing two extra sprites for left/right movement, whereas adding a 'black' column to your original sprite obviously only adds a single byte per row of sprite data. And it will do anybody's head in, working out the intermediate 'sprites'.
Note though that even the computer can't cope with the extreme edges without the missing side deflectors which are part of the not-revealed backdrop.)
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