Difference between revisions of "Map decoding in President"

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(New page: President's architecture is heavily inspired by that of ''Super Mario Bros.'' (SMB1). == President compared to SMB1 == Like SMB1: *Map is composed of "objects". *Map is decoded to 8-bit m...)
 
(President compared to SMB1: more)
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*Map is composed of "objects".
 
*Map is composed of "objects".
 
*Map is decoded to 8-bit metatile entries in a 2-screen-wide sliding window.
 
*Map is decoded to 8-bit metatile entries in a 2-screen-wide sliding window.
*Layer of "clouds"
+
*Layer of "clouds", or a repeating sequence of columns where each column has a 1x3-tile object at a given height.
 +
*Layer of "wall", or a 1x12-tile repeated object drawn on top of "clouds".
 +
*Four 64-entry metatile tables, one for each attribute value.
  
 
Unlike SMB1:
 
Unlike SMB1:
 
*The camera can move freely in the sliding window.
 
*The camera can move freely in the sliding window.
*Each map has a 32-entry directory containing the length of the start data
+
*Each map has a 32-entry directory containing the length of each screen's data.
*When a block is destroyed in one of the 512 columns of a map, a bit in a destruction buffer.
+
*The decoder can operate on either side of the sliding window.
 +
*When a block is destroyed in one of the 512 columns of a map, it sets a bit in a destruction buffer.
 +
*A lookup table supports translating objects in a destroyed column into destroyed objects.
 
*A Markov chain supports efficient decoding of objects taller than one block.
 
*A Markov chain supports efficient decoding of objects taller than one block.
 +
*Clouds can be drawn over wall, not just under it.
 +
*It's CHR RAM based; map types can replace tile data.
 +
*President is free software.

Revision as of 16:05, 6 March 2009

President's architecture is heavily inspired by that of Super Mario Bros. (SMB1).

President compared to SMB1

Like SMB1:

  • Map is composed of "objects".
  • Map is decoded to 8-bit metatile entries in a 2-screen-wide sliding window.
  • Layer of "clouds", or a repeating sequence of columns where each column has a 1x3-tile object at a given height.
  • Layer of "wall", or a 1x12-tile repeated object drawn on top of "clouds".
  • Four 64-entry metatile tables, one for each attribute value.

Unlike SMB1:

  • The camera can move freely in the sliding window.
  • Each map has a 32-entry directory containing the length of each screen's data.
  • The decoder can operate on either side of the sliding window.
  • When a block is destroyed in one of the 512 columns of a map, it sets a bit in a destruction buffer.
  • A lookup table supports translating objects in a destroyed column into destroyed objects.
  • A Markov chain supports efficient decoding of objects taller than one block.
  • Clouds can be drawn over wall, not just under it.
  • It's CHR RAM based; map types can replace tile data.
  • President is free software.