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95 lines
1.5 KiB
Plaintext
95 lines
1.5 KiB
Plaintext
Look reasonably well want at least 128 dots at 25Hz or so.
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Hard to do. Each dot has 4 muls and 2 divides which is expensive on 6502.
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Lookup tables? At some point they are so large you might as well just
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do a movie.
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Note even C64 version isn't accurate to the original.
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Initial implementation:
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512 dots, 2450 frames (35s when run at 70Hz which is what VGA does)
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256 dots, 2450 frames is ~1MB of data
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With this setup:
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$FF = all done
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$FE = new frame shadow
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$FD = new frame balls
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For X:
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$0..$27 (0..39) 00XX XXXX
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both
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1100 0000 - 1110 0111
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$C0-$E7
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top 1000 0000 - 1010 0111
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$80-$A7
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bottom
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0100 0000 - 0110 0111
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$40-$67
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new row
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0000 0000 - 0001 0111
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$00-$17
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For Y:
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$0..$17 (0..23) 000X XXXX
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01XX XXXX = new row
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specify top/bottom/both
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256 dots/2450 frames = 709,134 bytes
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skip factor 1 (none) = 41s
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skip factor 2 OK = 37s
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2450 frames @70Hz = 350 frames at 10Hz
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70=7*5*2
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without dot removal
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70fps 35fps 14fps 10fps 7fps 5fps
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256 dots: 709134 101304 70913 50652
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128 dots: 462169 66024 46216 33012
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64 dots: 290877 41533 29087 20776
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with dot removal
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70fps 35fps 14fps 10fps 7fps 5fps
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256 dots: 677907
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128 dots: 448966 44767
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64 dots: 285486 40694
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new compact format
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70fps 35fps 14fps 10fps 7fps 5fps
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256 dots: 76516 53447 38227
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128 dots: 52456 36632
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64 dots: 120183 34299
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40k
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zx02 version:
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70fps 10fps 7fps 5fps
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256 dots: 1.4MB
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128 dots: 1.4MB
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actual version:
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requires 4 multiplies and 2 divides for each point
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have a routine 250 cycles for multiply
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250x6x256 = 384000 = 2 fps
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