webgl shader glsl built-in functions

 1. Functions related to angle

The following is the function related to the angle

function	parameter	describe
sin(x)	radian	sine function
cos(x)	radian	cosine function
tan(x)	radian	Tangent function
asin(x)	radian	arcsine function
acos(x)	radian	arccosine function
time(x)	radian	arctangent function
radians(x)	angle	Angles to radians
degrees(x)	radian	Convert radians to degrees

 2. Mathematical functions

This type is mainly for the operation of exponential logarithmic power function

function	describe
pow(x,y)	x to the yth power. If x is less than 0, the result is undefined. Likewise, if x=0 and y<=0, the result is undefined.
exp(x)	e to the xth power
log(x)	Computes the value of y such that x is equal to e raised to the yth power. If the value of x is less than 0, the result is undefined.
exp2(x)	Calculate 2 to the power of x
log2(x)	Calculates the value of y such that x is equal to 2 to the power of y. If the value of x is less than 0, the result is undefined.
sqrt(x)	Computes the square root of x. If x is less than 0, the result is undefined.
inversesqrt(x)	Computes the value of one of the roots of x. If x is less than or equal to 0, the result is undefined.

 3. Common functions

Here are commonly used functions, similar to built-in functions in js

function	describe
abs(x)	returns the absolute value of x
sign(x)	If x>0, return 1.0; if x=0, return 0, if x<0, return -1.0
floor(x)	Returns the largest integer value less than or equal to x
ceil(x)	Returns the smallest integer value greater than or equal to x
fract(x)	Returns x-floor(x), which returns the fractional part of x
mod(x, y)	Returns the modulus of x and y
min(x, y)	Returns the lesser value of x and y.
max(x, y)	Returns the greater of x and y.
clamp(x, minVal, maxVal)	Clamp the x value between minVal and maxVal, which means return minVal when x<minVal, return maxVal when x>maxVal, and return x when x is between minVal and maxVal
mix(x, y, a)	Returns a linear mixture of x and y, such as: x*(1−a)+y*a
step(edge, x)	If x < edge, return 0.0, otherwise return 1.0
smoothstep(edge0, edge1, x)	If x <= edge0, return 0.0; if x >= edge1 return 1.0; if edge0 < x < edge1, perform a smooth Hermitian difference between 0 and 1. If edge0 >= edge1, the result is undefined.

4. Geometric functions

Here are functions related to lengths, distances, vectors, etc.

length(x)	Returns the length of the vector x
distance(p0,p1)	Calculate the distance between vectors p0, p1
dot	Dot product between vectors x, y
cross(x, y)	Cross product between vectors x, y
normalize(x)	Normalizes a vector, returning a vector with the same direction as x but length 1
faceforward(N, I, Nref)	If the dot product of Nref and I is less than 0, return N; otherwise, return -N;
reflect(I, N)	return reflection vector
refract(I, N, eta)	Returns the refraction vector