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

SDL_HapticDirection

Structure that represents a haptic direction.

Header File

Syntax

typedef struct SDL_HapticDirection
{
    Uint8 type;         /**< The type of encoding. */
    Sint32 dir[3];      /**< The encoded direction. */
} SDL_HapticDirection;

Remarks

This is the direction where the force comes from, instead of the direction in which the force is exerted.

Directions can be specified by:

SDL_HAPTIC_POLAR : Specified by polar coordinates.
SDL_HAPTIC_CARTESIAN : Specified by cartesian coordinates.
SDL_HAPTIC_SPHERICAL : Specified by spherical coordinates.

Cardinal directions of the haptic device are relative to the positioning of the device. North is considered to be away from the user.

The following diagram represents the cardinal directions:

               .--.
               |__| .-------.
               |=.| |.-----.|
               |--| ||     ||
               |  | |'-----'|
               |__|~')_____('
                 [ COMPUTER ]


                   North (0,-1)
                       ^
                       |
                       |
 (-1,0)  West <----[ HAPTIC ]----> East (1,0)
                       |
                       |
                       v
                    South (0,1)


                    [ USER ]
                      \|||/
                      (o o)
                ---ooO-(_)-Ooo---

If type is SDL_HAPTIC_POLAR, direction is encoded by hundredths of a degree starting north and turning clockwise. SDL_HAPTIC_POLAR only uses the first dir parameter. The cardinal directions would be:

North: 0 (0 degrees)
East: 9000 (90 degrees)
South: 18000 (180 degrees)
West: 27000 (270 degrees)

If type is SDL_HAPTIC_CARTESIAN, direction is encoded by three positions (X axis, Y axis and Z axis (with 3 axes)). SDL_HAPTIC_CARTESIAN uses the first three dir parameters. The cardinal directions would be:

North: 0,-1, 0
East: 1, 0, 0
South: 0, 1, 0
West: -1, 0, 0

The Z axis represents the height of the effect if supported, otherwise it's unused. In cartesian encoding (1, 2) would be the same as (2, 4), you can use any multiple you want, only the direction matters.

If type is SDL_HAPTIC_SPHERICAL, direction is encoded by two rotations. The first two dir parameters are used. The dir parameters are as follows (all values are in hundredths of degrees):

Degrees from (1, 0) rotated towards (0, 1).
Degrees towards (0, 0, 1) (device needs at least 3 axes).

Example of force coming from the south with all encodings (force coming from the south means the user will have to pull the stick to counteract):

 SDL_HapticDirection direction;

 // Cartesian directions
 direction.type = SDL_HAPTIC_CARTESIAN; // Using cartesian direction encoding.
 direction.dir[0] = 0; // X position
 direction.dir[1] = 1; // Y position
 // Assuming the device has 2 axes, we don't need to specify third parameter.

 // Polar directions
 direction.type = SDL_HAPTIC_POLAR; // We'll be using polar direction encoding.
 direction.dir[0] = 18000; // Polar only uses first parameter

 // Spherical coordinates
 direction.type = SDL_HAPTIC_SPHERICAL; // Spherical encoding
 direction.dir[0] = 9000; // Since we only have two axes we don't need more parameters.

Version

This struct is available since SDL 3.1.3.