Reference

The whole shader language, on one page.

The block

SHADER "name"
    USE NUMBER name [DEFAULT number]
    USE COLOR name [DEFAULT RGB(r, g, b)]
    USE IMAGE name
    WHEN DRAWING
        name = expression
        SET COLOR = expression
    END WHEN
END SHADER

Line	Means
`SHADER "name"` … `END SHADER`	Defines a shader called `name`, or replaces the one already called that.
`USE NUMBER name [DEFAULT n]`	A number setting. Without `DEFAULT` it’s 0. `n` is a plain number, with no minus.
`USE COLOR name [DEFAULT RGBA(r, g, b, a)]`	A color setting, four numbers; `RGB(r, g, b)` for an opaque one. Without `DEFAULT` it’s opaque black. Given as three or four numbers from 0 to 1: `(1.0, 0.5, 0.0)` or a list.
`USE IMAGE name`	A picture setting, given by its name in `shader_params`, read with `SAMPLE(name, uv)`. Up to 4.
`WHEN DRAWING` … `END WHEN`	The code, run once for every pixel.
`name = expression`	Makes or changes a variable.
`SET COLOR = expression`	The pixel’s color: four parts, 0 to 1. The last one wins; with none, the pixel keeps `IMAGE`.
`' comment`	To the end of the line.

What a pixel knows

Word	Parts	Is
`IMAGE`	4	The color the pixel was going to be.
`UV`	2	Where it is on what’s being drawn: `(0, 0)` top left, `(1, 1)` bottom right. On an animated sprite, on the frame.
`SCREEN`	2	Where it is on the screen, in the game’s pixels, from `(0, 0)` at the game’s top left.
`SCREEN_SIZE`	2	The game’s size, in its own pixels, as `SCREEN` set it.
`TIME`	1	Seconds since the renderer started.
`TICK`	1	Frames drawn since this shader went on this layer or sprite.

Functions

Function	Gives
`RGBA(r, g, b, a)`	A color.
`RGB(r, g, b)`	A solid color.
`VEC2(x, y)`, `VEC3(x, y, z)`, `VEC4(x, y, z, w)`	A vector.
`OWNTEXTURE(uv)`	The color of the shader’s own picture at `uv`.
`SAMPLE(name, uv)`	The color of a `USE IMAGE` picture at `uv`.
`PX(x, y)`	`x` pixels across and `y` down, as a `UV`, in the picture’s own pixels.
`RND(x)`, `RND(x, y)`	A number from 0 to 1 that looks random, the same every time for the same numbers.
`ABS(x)`	`x` without its minus.
`FLOOR(x)`	`x` rounded down to a whole number.
`FRACT(x)`	What comes after the point: `x - FLOOR(x)`.
`SIN(x)`, `COS(x)`	Sine and cosine, in radians.
`SQRT(x)`	Square root.
`POW(x, y)`	`x` to the power `y`.
`MIN(a, b)`, `MAX(a, b)`	The smaller, the bigger.
`CLAMP(x, low, high)`	`x`, kept from `low` to `high`.
`MIX(a, b, t)`	`a` at 0, `b` at 1, between in between.
`STEP(edge, x)`	0 if `x` is under `edge`, otherwise 1.
`SMOOTHSTEP(low, high, x)`	0 to 1, smoothly, as `x` goes from `low` to `high`.
`LENGTH(v)`	How long a vector is.
`DOT(a, b)`	Parts multiplied in pairs, added up.
`NORMALIZE(v)`	`v`, 1 long.

Every function but RGBA, RGB, the VECs, OWNTEXTURE, SAMPLE, PX, RND, LENGTH and DOT works on a vector part by part, as well as on a number. When it takes more than one value, they’re all the same size, except the last of MIX, which can be a number.

Sums

+ - * /, with * and / first, brackets before both, and - in front to turn a number around. Vector and vector, of the same size, part by part; vector and number, the number in every part.

Swizzles

.r .g .b .a or .x .y .z .w, one to four of them, in any order, on a name, a word, or brackets: c.bgr, UV.yx, (UV * 2.0).x.

Putting a shader on

	On	Settings	Off
A layer	`SET LAYER n !! shader("name")`	`!! shader_params({...})`, with `shader` or by itself	`!! clear_shader`
A sprite	`SET SPRITE n !! shader("name")`	`!! shader_params({...})`, with `shader`	`!! clear_shader`
A shape, with a `texture`	`SET POLYGON n !! shader("name")`	`!! shader_params({...})`, with `shader`	`!! clear_shader`
A behavior	`USE SHADER "name"`	`!! param("name") start(a) to(b) duration(ticks) [loop]`	when the behavior ends
A transition	`CLS [color] !! effect_shader("name") [speed(n)]`	`progress`, `target_r`, `target_g`, `target_b`, `target_a`, filled in	when it’s done

In shader_params, a number goes to a USE NUMBER setting, three or four numbers in brackets or a list to a USE COLOR one, and a picture’s name, as a string, to a USE IMAGE one. A name the shader doesn’t have, or a value of the wrong kind, stops the program and says which settings the shader takes.

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