GLSL Help

This help only covers the parts of GLSL ES that are relevant for Shadertoy. For the complete specification please have a look at GLSL ES specification

Language:

Preprocessor: # #define #undef #if #ifdef #ifndef #else #elif #endif #error #pragma #extension #version #line
Operators: () + - ! * / % << >> < > <= >= == != && ||
Comments: // /* */
Types: void bool int float vec2 vec3 vec4 bvec2 bvec3 bvec4 ivec2 ivec3 ivec4 mat2 mat3 mat4 sampler2D
Function Parameter Qualifiers: [none], in, out, inout
Global Variable Qualifiers: const
Vector Components: .xyzw .rgba .stpq
Flow Control: if else for return break continue
Output: vec4 gl_FragColor
Input: vec4 gl_FragCoord

Built-in Functions:

type radians (type degrees)
type degrees (type radians)
type sin (type angle)
type cos (type angle)
type tan (type angle)
type asin (type x)
type acos (type x)
type atan (type y, type x)
type atan (type y_over_x)

type pow (type x, type y)
type exp (type x)
type log (type x)
type exp2 (type x)
type log2 (type x)
type sqrt (type x)
type inversesqrt (type x)

type abs (type x)
type sign (type x)
type floor (type x)
type ceil (type x)
type fract (type x)
type mod (type x, float y)
type mod (type x, type y)
type min (type x, type y)
type min (type x, float y)
type max (type x, type y)
type max (type x, float y)
type clamp (type x, type minV, type maxV)
type clamp (type x, float minV, float maxV)
type mix (type x, type y, type a)
type mix (type x, type y, float a)
type step (type edge, type x)
type step (float edge, type x)
type smoothstep (type a, type b, type x)
type smoothstep (float a, float b, type x)
mat matrixCompMult (mat x, mat y)

float length (type x)
float distance (type p0, type p1)
float dot (type x, type y)
vec3 cross (vec3 x, vec3 y)
type normalize (type x)
type faceforward (type N, type I, type Nref)
type reflect (type I, type N)
type refract (type I, type N,float eta)

bvec lessThan(vec x, vec y)
bvec lessThan(ivec x, ivec y)
bvec lessThanEqual(vec x, vec y)
bvec lessThanEqual(ivec x, ivec y)
bvec greaterThan(vec x, vec y)
bvec greaterThan(ivec x, ivec y)
bvec greaterThanEqual(vec x, vec y)
bvec greaterThanEqual(ivec x, ivec y)
bvec equal(vec x, vec y)
bvec equal(ivec x, ivec y)
bvec equal(bvec x, bvec y)
bvec notEqual(vec x, vec y)
bvec notEqual(ivec x, ivec y)
bvec notEqual(bvec x, bvec y)
bool any(bvec x)
bool all(bvec x)
bvec not(bvec x)

vec4 texture2D(sampler2D sampler, vec2 coord )
vec4 texture2D(sampler2D sampler, vec2 coord, float bias)
vec4 textureCube(samplerCube sampler, vec3 coord)
vec4 texture2DProj(sampler2D sampler, vec3 coord )
vec4 texture2DProj(sampler2D sampler, vec3 coord, float bias)
vec4 texture2DProj(sampler2D sampler, vec4 coord)
vec4 texture2DProj(sampler2D sampler, vec4 coord, float bias)

type dFdx( type x ), dFdy( type x )
type fwidth( type p )

How-to

Use structs: struct myDataType { float occlusion; vec3 color; }; myDataType myData = myDataType(0.7, vec3(1.0, 2.0, 3.0));
Initialize arrays: arrays cannot be initialized in WebGL.
Do conversions: int b = 3; float b = float(a);
Do component swizzling: vec4 a = vec4(1.0,2.0,3.0,4.0); vec4 b = a.zyyw;
Access matrix components: mat4 m; m[1] = vec4(2.0); m[0][0] = 1.0; m[2][3] = 2.0;

Be careful!

the f suffix for floating pont numbers: 1.0f is illegal in GLSL. You must use 1.0
saturate(): saturate(x) doesn't exist in GLSL. Use clamp(x,0.0,1.0) instead
pow/sqrt: please don't feed sqrt() and pow() with negative numbers. Add an abs() or max(0.0,) to the argument
variables: initialize your variables! Don't assume they'll be set to zero by default
functions: don't call your functions the same as some of your variables

Shadertoy specific inputs

vec3	iResolution	image	The viewport resolution (z is pixel aspect ratio, usually 1.0)
float	iGlobalTime	image/sound	Current time in seconds
float	iChannelTime[4]	image	Time for channel (if video or sound), in seconds
vec3	iChannelResolution0..3	image/sound	Input texture resolution for each channel
vec4	iMouse	image	xy = current pixel coords (if LMB is down). zw = click pixel
sampler2D	iChannel{i}	image/sound	Sampler for input textures i
vec4	iDate	image/sound	Year, month, day, time in seconds in .xyzw
float	iSampleRate	image/sound	The sound sample rate (typically 44100)

Shadertoy outputs

For image shaders, the regular gl_FragColor is used as output channel. It is not for now mandatory but recommended to leave the alpha channel to 1.0;

For sound shaders, the mainSound() function is supposed to return a vec2 to as an output containing the lsft and right (stereo) sound channel wave data.