SCN

The SCN callback allows you to execute code between the rendering of each scan line; for example, to manipulate the palette. This makes it theoretically possible to use a different palette for every scan line.

Usage:

function SCN(scanline)
  -- your code here
end

Parameters

scanline The scan line about to be drawn (0..135)

Example

The following example displays all 256 possible shades of gray. This can be done with any color.

-- title:  256 shades of gray
-- author: Marcuss2, fixed by nesbox
-- desc:   Showoff of grayscale
-- script: lua
-- input:  mouse

ADDR = 0x3FC0
palette = 0

function addLight()
 for i=0, 15 do
  for j=0, 2 do
   poke(ADDR+(i*3)+j, palette)
  end
  palette = palette + 1
 end	
end

function SCN(scnline)
 if scnline % 8 == 0 then
  addLight()
 end
end

function init()
 for i=0, 16 do
  rect(i*15, 0, 15, 240, i)
 end
end

init()

function TIC()
 palette = 0
end