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Mosaic is a screen pixellation effect. The mosaic register is located at 2106h, and it can be enabled or disabled on a per-background basis via bits 0-3 (called the mosaic mode select). When enabled for a given background, the output background color (which will then be fed to the compositor and combined with all the other possibly mosaicized backgrounds) of the pixel at screen position (H,V) is:

output_color(H,V) = input_color(floor(H/size)*size, floor(V/size)*size)

where size is the value of bits 4-7 of 2106h plus one. Thus, for each mosaicized background, the shaded output consists of a grid of solid-colored squares where each entire square's color matches that of its top-leftmost input pixel.

The first mosaic square's location is always (0,0) so that the upper-left corner of the square is coincident with the upper-left corner of the screen, disregarding overscan. Sprites are unaffected by the mosaic filter. All background modes support mosaic.[7]

The mosaic filter has a horizontal and vertical subsystem:

  • The horizontal mosaic latches remember the color of the top-leftmost pixel of each mosaicized block.
  • The vertical mosaic latch remembers what the value of the PPU vertical scanline counter was at the top of each mosaicized block.[3]

On Mode 7's EXTBG, vertical mosaic is enabled when bit 0 of the mosaic register is set, and horizontal mosaic is enabled when bit 1 is set. [4]


Game Name Mosaic Usage Animated GIF
Animaniacs upon opening a door
Axelay when the Stage 3 boss' final form takes damage
Final Fantasy III (US) when trying to select a disabled menu option and upon entering a battle mosaic FF3.gif FF3 mosaic battle.gif
Final Fantasy Mystic Quest upon entering battles and before/after loading new sections of the map mosaic FFMQ.gif
The Legend of Zelda: A Link to the Past
The Magical Quest Starring Mickey Mouse when the final boss takes damage, and on the walls of that same battle
Star Ocean upon entering every battle
Street Fighter II on the title screen logo Street Fighter II (USA) title mosaic.gif
Super Mario World after selecting and entering a level mosaic SMW.gif

Apparent Resolution

This table describes how many complete mosaicized blocks appear on each axis when the mosaic filter is applied (the "apparent" screen resolution, in other words) disregarding overscan. The number of spare pixels off to the right and/or bottom of the screen that make up the last incomplete blocks when the block size does not evenly divide the screen is also given.

$2106.4-7 Mosaic Block Size Image # of rows of complete blocks # of columns of complete blocks # of rows of spare pixels # of columns of spare pixels
0 1 mosaic 1x1.png 224 256 0 0
1 2 mosaic 2x2.png 112 128 0 0
2 3 mosaic 3x3.png 74 85 2 1
3 4 mosaic 4x4.png 56 64 0 0
4 5 mosaic 5x5.png 44 51 4 1
5 6 mosaic 6x6.png 37 42 2 4
6 7 mosaic 7x7.png 32 36 0 4
7 8 mosaic 8x8.png 28 32 0 0
8 9 mosaic 9x9.png 24 28 8 4
9 10 mosaic 10x10.png 22 25 4 6
10 11 mosaic 11x11.png 20 23 4 3
11 12 mosaic 12x12.png 18 21 8 4
12 13 mosaic 13x13.png 17 19 3 9
13 14 mosaic 14x14.png 16 18 0 4
14 15 mosaic 15x15.png 14 17 14 1
15 16 mosaic 16x16.png 14 16 0 0

Anomie mentions these two mosaic block patterns for Mode 7 EXTBG:

mosaic 16x1.png mosaic 1x16.png

See Also

External Links


  1. setting example: page 2-4-1 of Book I of the official Super Nintendo development manual
  2. https://problemkaputt.de/fullsnes.htm#snesppubgcontrol
  3. https://board.zsnes.com/phpBB3/viewtopic.php?p=204966#p204966
  4. anomie's register doc
  5. bit-by-bit breakdown of the mosaic register: page 2-27-3 lbid
  6. display example of mosaic effect: Appendix A-7 lbid
  7. Appendix A-5 lbid