(This is the documentation for SDL3, which is under heavy development and the API is changing! SDL2 is the current stable 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

Defined in SDL_stdinc.h, but apps should use #include <SDL3/SDL.h>

Syntax

double SDL_atan2(double y, double x);

Function Parameters

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

Return Value

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.

Version

This function is available since SDL 3.0.0.