pouët.net

Dither City by Taquart
[nfo]
screenshot added by 0xF on 2021-03-14 14:07:04
platform :
type :
release date : march 2021
release party : Lovebyte 2021
compo : combined 32b
ranked : 13th
  • 4
  • 1
  • 0
popularity : 39%
 39%
  • 0.80
alltime top: #40000
added on the 2021-03-14 14:07:04 by 0xF 0xF

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This prod is 32 bytes of code plus a mandatory 6-byte header, which was excluded by compo rules. This makes the whole file 38 bytes long, hence I selected two categories on pouet.net.
Originally the prod was smaller, but not that fast.
added on the 2021-03-14 14:17:49 by 0xF 0xF
great
rulez added on the 2021-03-14 14:29:24 by Blast! Blast!
Cool noisy dither pattern
rulez added on the 2021-03-14 15:03:38 by Optimus Optimus
quite nice, but the hellmood's version is more elegant
rulez added on the 2021-03-14 17:21:13 by gorgh gorgh
Quote:
This prod is 32 bytes of code plus a mandatory 6-byte header, which was excluded by compo rules. This makes the whole file 38 bytes long, hence I selected two categories on pouet.net.
Originally the prod was smaller, but not that fast.


Please write more technical details behind this entrie. How it is practically done?
rulez added on the 2021-03-14 17:24:00 by ded^RMDA ded^RMDA
It's a linear gradient from black to 75% white, using hardware-accelerated pseudo-random dithering.

It's very fast for 320x192 on a 40-year-old hardware because:
1. The 8-bit pseudo-random number is retrieved from the POKEY chip's RANDOM register which gets updated every cycle. The pixel value is computed by comparing the Y coordinate with the value of RANDOM: pixel_is_white=(RANDOM<=Y).
2. It writes directly to screen RAM. The OS "plot" would be slower by several orders of magnitude.

The source is on GitHub.

This technique can be used for any 256-level grayscale effect in hires. It takes one instruction (compare with RANDOM) to convert the grayscale level in one of the three CPU registers to the dithered pixel in the C flag.
added on the 2021-10-14 09:53:39 by 0xF 0xF

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