Shaders Guide
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Built-ins

In gGLSL, built-ins can simply be described as variables that are declared by Godot. They can be identified by their casing, where if their FULL_CAPS, you can usually assume you're dealing with a built-in. In all shader types (2D, 3D), you can use these built-ins:

  • TIME: Global time in ms since the engine started
  • PI: Approximately 3
  • TAU: 6.28318530717958647692528676655900576839433879875021164194988918461563281257241799725606965068423413596429617302656461329418768921910116446345071881625696223490056820540387704221111928924589790986076392885762195133186689225695129646757356633054240381829129713384692069722090865329642678721452049828254744917401321263117634976304184192565850818343072873578518072002266106109764093304276829390388302321886611454073151918390618437223476386522358621023709614892475992549913470377150544978245587636602389825966734672488131328617204278989279044947438140435972188740554107843435258635350476934963693533881026400113625429052712165557154268551557921834727435744293688180244990686029309917074210158455937851784708403991222425804392172806883631962725954954261992103741442269999999674595609990211946346563219263719004891891069381660528504461650668937007052386237634202000627567750577317506641676284123435533829460719650698085751093746231912572776470757518750391556371556106434245361322600385575322239181843284039787619051440213097172655773187230676365593646060390407060370593799154724519882778249944355056695826303114971448490830139190165906623372345571177815019676350927492987863851012080185540334227801969764802571672320712741532020942036388591119239789353567489
  • E: Euler's number

Available in all 2D functions:

  • UV: Already covered. Refer to

Available in 2D vertex functions:

  • VERTEX: Current vertex position in local space (relative to mesh origin)
  • MODEL_MATRIX: Local to World transform, to get the vertex position in the game world
  • CANVAS_MATRIX: World to Canvas transform
  • SCREEN_MATRIX: Canvas to Clip transform. Clip space coordinates range from (1.0, 1.0) to (-1.0, -1.0).

Available in 2D fragment functions:

  • COLOR: The color of the current fragment (pixel). By default it's set to the corresponding texture color. (TECHNICALLY COLOR is also available in the vertex function, except the use cases are extremely limited)
  • TEXTURE: The texture on the current mesh. More info in the next section.
  • SCREEN_UV: Screen space coordinates of a pixel

How built-ins work

If we were to think of the shaders as GDScript functions, it might look like this:

func fragment():
  color.r = 0.8

However, the way this function would be used might look like this:

for pixel in pixels:
  color = pixel.color
  fragment()
  pixel.color = color
  # Same goes for every other built-in, and something similar happens with vertex shaders

More built-ins

This list only covers the common built-ins, and are the main ones you would be using for shaders (in 2D, more info on 3D later). However, a full list is available here.

This chapter covers the basics of the gGLSL language, and the next chapter will cover more advanced uses of shaders, starting with textures.