Types

Here is a non-exhaustive list of the most common ESSL types:

void: For functions that do not return a value or for an empty parameter list
bool: A conditional type, taking on values of true or false
int: A signed integer
float: A single floating-point scalar
vec2: A two-component floating-point vector
vec3: A three-component floating-point vector
vec4: A four-component floating-point vector
bvec2: A two-component Boolean vector
bvec3: A three-component Boolean vector
bvec4: A four-component Boolean vector
ivec2: A two-component integer vector
ivec3: A three-component integer vector
ivec4: A four-component integer vector
mat2: A 2×2 floating-point matrix
mat3: A 3×3 floating-point matrix
mat4: A 4×4 floating-point matrix
sampler2D: A handle for accessing a 2D texture
sampler3D: A handle for accessing a 3D texture
samplerCube: A handle for accessing a cube-mapped texture
struct: Used to declare custom data structures based on standard types

ESSL

There are many other types and features that the OpenGL ES 3.0 shading language provides. Here is a useful guide that covers many of its core features: https://www.khronos.org/files/opengles3-quick-reference-card.pdf.

An input variable will have one of the qualifiers followed by one type. For example, we will declare our uLightColor variable as follows:

uniform vec4 uLightColor;

This means that the uLightColor variable is a uniform vector with four components.

The GLSL and ESSL Naming Convention

Convention dictates that we prefix shader variables with their type. This makes for clear and readable shader code. For example, for a given color uniform, you would name the variable uLightColor. For a position varying, vNormal. For a normal attribute, aVertexNormal.