Converting shaders

From GLSL to Godot shaders

Shading languageGodot Engine documentation

Godot 3.5 documentation about shaders

iResolution

SCREEN_PIXEL_SIZE is the inverse of iResolution

iResolution.x == (1.0 / SCREEN_PIXEL_SIZE.x)

UV

Usually on shader toy you will see UV from fragcoord

vaec uv = FRAGCOORD.xy * SCREEN_PIXEL_SIZE;

But in Godot if you want to make shader draw things in object coordinates, then just use

vec2 uv = UV;

mat2

If you have an error message like

Invalid arguments for built-in function: mat2(float, float, float, float)

then replace the way 2D matrix is created. It must be 2 vectors of floats, but not 4 floats

mat2(a,b,c,d) => mat2(vec2(a,b), vec2(c,d))

Helper functions

Unknown identifier in expression: SCREEN_PIXEL_SIZE

For example, SCREEN_PIZEL_SIZE only defined in main fragment() function, pass it as argument to other functions.