DRAFT

# SDL_HapticDirection

A structure that contains a haptic direction.

## Data Fields

 Uint8 type the type of encoding; see Remarks for details Sint32 dir the encoded direction; see Remarks for details

## Code Examples

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.
```

## Remarks

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

Cardinal directions of the haptic device are relative to the positioning of the device. North is considered to be away from the user. South is toward the user, east is right, and west is left of 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---```

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

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)

None: SDL_HapticDirection (last edited 2016-05-12 20:46:29 by PhilippWiesemann)

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