GLSL Syntax

Further information for people interesting in writing GLSL

Additional shader example for understanding syntax

#ifdef GL_ES
precision highp float;
#endif

IN vec2 texCoord;

// Uniform variables: 
// bridge between  CPU - GPU that allows mapping external information 
// For example: time
uniform float uTime;


{{MODULES_HEAD}}

void main()
{
  
    /* Declaration of variables
       type name = value; */

    // Real numbers
    float number_0 = 1.0; // with dot
    int number_1 = 1;

    // Vectors 
    // 2 dimensions [_ ,_ ]
    vec2 v2_0 = vec2(0.,1.);
    vec2 v2_1 = vec2(number_0,number_1);

    //3 dimensions [_ ,_ ,_ ]
    vec3 v3_0 = vec3(0.,0.5,1.);
    vec3 v3_1 = vec3(v2_0,1.);
    vec3 v3_2 = vec3(v2_0,number_0);

    //4 dimensions [_ ,_ ,_ ,_ ]
    vec4 v4_0 = vec4(0.,0.25,0.5,1.);
    vec4 v4_1 = vec4(v2_0,v2_1);
    vec4 v4_2 = vec4(v3_0,0.);

    // Referencing vectors information
    // [r, g, b, a] || [x , y , z , w] 

    float numero_2 = v4_0.r; // is equivalent to v4_0.x
    vec2 v2_2 = v4_0.rg;     // is equivalent to v4_0.xy
    vec3 v3_3 = v4_0.gbr;    // is equivalent to v4_0.yzx

    gl_FragColor = vec4(0.5); // [ (r, g ,b , a) ]  with values in between 0. y 1.
}

Functions to explore

Complete list of functions:

• https://www.shaderific.com/glsl-functions
• https://thebookofshaders.com/glossary/

FUNCTIONS

Trigonometry

cos(x)

sin(x)

tan(x)

Power pow(x, 0.5) == sqrt(x)

pow(x, 1.)

pow(x, 2.)

pow(x, n) for any n:=number

sqrt(x): square root

inversesqrt(x) 1./sqrt(x)

Exponentials

exp(x) : base 10

exp2(x): base 2

Logarithms

log(x) : base 10

log2(x) : base 2

Geometry

length(x): length of a vector in the Euclidean norm.

distance(x,y): distance between x and y

dot(x,y): inner product between x and y (scalar product)

Other

abs(x) : absolute value of x. E.g. abs(1)=1, abs(-1)=1

sign(x) : sign of x. E.g. sign(1)=1 sign(-1)=0

floor(x) : the nearest whole number that is less than x. Ex: floor(3.14) = 3

ceiling(x):the nearest integer that is greater than x. Example: ceiling(3.14) = 4

fract(x): the fractional part of x. Example: fract(3.14)= .14;

min(a,b): minimum value between a and b

max(a,b): minimum value between a and b

clamp(x, a, b): if x is less than a returns a, if x is greater than b returns b, otherwise returns x.

mod(x, y): returns the remainder of the division of x divided by y`

mix(x, y, a): x*(1.-a)+ya

step(x, a): returns 0 if x <= a, and returns 1 if x > a.

smoothstep(x,a,b): returns 0 if x<a, interpolates between 0 and 1 if a<x<=b, returns 1 if x > b.

Example for use in function explorer:

float y = cos(cos(cos(xx+u_time*.1),1.5)*10.-u_time);