obtusity

Please send any questions about brush scripts, but the basic idea is start with a skeleton of:

function main(x, y, p)
   return 0
end

Then add whatever code you need into main to accomplish your desires.

... and I know that's worse then saying "draw a stick figure, then add all the details to draw what you want", but without a more specific direction (or at least an art style) that's about all you can say.

A better starting skeleton might be something like:

lastDrawX = 0
lastDrawY = 0
firstDraw = true

function main(x, y, p)
 local width = bs_width()
 local updateDist = width

 if not firstDraw then
   local distance = bs_distance(lastDrawX - x, lastDrawY - y)
   if distance < updateDist then
     return 0
   end
 end

 local r, g, b = bs_fore()
 local opacity = bs_opaque() * 255
 bs_ellipse(x, y, width, width, 0, r, g, b, opacity)

 lastDrawX = x
 lastDrawY = y
 firstDraw = false

 return 1
end

... and replace the bs_ellipse with whatever you want to do.

Alternatively, start with one of the examples at d.hatena.ne.jp/MDIAPP/20100311

Warning: brush scripts can do amazing things, but they have limits, in the same way computer-generated music is still mostly terrible compared to human-composed music - they can only work within the one layer, they do not work well, if at all, with bitmaps, and they can be slower than other brushes. There are probably other limitations also.