Colour and monochrome

A NeoTrellis grid with my firmware shows colour. A monome grid shows 16 brightness levels of one colour. A script can work on both: it draws in colour where colour exists, and falls back to brightness levels where it doesn't.

color_fallback_demo.lua on a NeoTrellis grid.

The functions

Function	NeoTrellis firmware	Monome grid (iii)
grid_led(x, y, level), grid_led_all(level)	Yes, in the current tint	Yes
grid_color(r, g, b)	Sets the tint for grid_led and grid_led_all	Doesn't exist
grid_led_rgb(x, y, r, g, b)	Sets one pad's colour, ignoring the tint	Doesn't exist
grid_color_intensity(level)	Overall brightness	Doesn't exist

On a monome grid, calling a function that doesn't exist stops the script with an error. Check first:

if grid_color then grid_color(255, 120, 20) end

To test your script without colour, pick ◐ View → Monochrome in the emulator: the colour functions disappear, as on a monome grid, and a missing check shows up as an error. On hardware, viii does the same, since it only has grid_led.

color_fallback_demo.lua on the NeoTrellis grid after testing its monochrome version in viii.

Three ways to use colour

Approach	Use it for	On a monome grid
grid_color + grid_led	One colour for the whole grid	Same brightness levels, without the colour
spx helper (below)	Several colours, with a fallback	Each colour becomes a brightness level
grid_led_rgb only	Colour that only makes sense on RGB	Nothing lights up

One colour for the whole grid

Set the tint once and draw as you would in monochrome:

if grid_color then grid_color(255, 120, 20) end -- amber

grid_led(1, 1, 15) -- bright amber
grid_led(2, 1, 8)  -- mid amber
grid_refresh()

The default tint is white. On my firmware, people can also pick a default tint at startup (see Getting started). Scripts that set their own colours aren't affected by it.

Several colours, with a fallback

Draw every pad through one helper. On a NeoTrellis grid it sets the colour; elsewhere it turns the brightest channel into a level from 4 to 15:

local W, H = grid_size_x(), grid_size_y()

local function spx(x, y, r, g, b)
  if x < 1 or x > W or y < 1 or y > H then return end
  if grid_led_rgb then
    grid_led_rgb(x, y, r, g, b)
  else
    -- Levels 1–3 can't be seen on NeoTrellis LEDs and are very dim on monome
    -- grids, so anything that isn't black gets at least level 4.
    local level = math.floor(math.max(r, g, b) / 17)
    if level < 4 and (r > 0 or g > 0 or b > 0) then level = 4 end
    grid_led(x, y, level)
  end
end

spx(1, 1, 255, 80, 20) -- orange, or level 15
spx(2, 1, 20, 100, 255) -- blue, or level 15
spx(3, 1, 0, 40, 0)    -- dark green, or level 4

The contrast between your colours becomes the contrast between brightness levels. Full example: color_fallback_demo.lua.

Dim colours on NeoTrellis

Each NeoTrellis pad mixes red, green and blue LEDs. At low brightness, the weaker channels drop out before the others, so a tinted colour can change hue. Orange (lots of red, some green) turns red when the green fades out first. Measured with grid_led and a tint:

Level	What you see
1–2	Nothing
3	First visible level; the colour may be off
4–7	Visible, but cyan and blue tints can look orange or red
8–15	Accurate colour

grid_led_rgb keeps its colour better at low brightness.

color-threshold-test.lua: tinted grid_led on the left, grid_led_rgb on the right.

The emulator doesn't show these shifts. What helps:

• Keep tinted pads at level 8 or higher.
• For dim colours, use grid_led_rgb and keep every channel you need above about 20.
• Use level 0 for off, and at least level 4 for on.

The thresholds can vary between NeoTrellis boards. To check yours, run color-threshold-test.lua. color-workaround-demo.lua shows the grid_led_rgb workaround.