(This is the documentation for SDL3, which is the current stable version. SDL2 was the previous version!)

SDL_atan2

Compute the arc tangent of y / x, using the signs of x and y to adjust the result's quadrant.

Header File

Syntax

double SDL_atan2(double y, double x);

Function Parameters

double	y	floating point value of the numerator (y coordinate).
double	x	floating point value of the denominator (x coordinate).

Return Value

(double) Returns arc tangent of of y / x in radians, or, if x = 0, either -Pi/2, 0, or Pi/2, depending on the value of y.

Remarks

The definition of z = atan2(x, y) is y = x tan(z), where the quadrant of z is determined based on the signs of x and y.

Domain: -INF <= x <= INF, -INF <= y <= INF

Range: -Pi/2 <= y <= Pi/2

This function operates on double-precision floating point values, use SDL_atan2f for single-precision floats.

To calculate the arc tangent of a single value, use SDL_atan.

This function may use a different approximation across different versions, platforms and configurations. i.e, it can return a different value given the same input on different machines or operating systems, or if SDL is updated.

Thread Safety

It is safe to call this function from any thread.

Version

This function is available since SDL 3.1.3.