Unigine.quat Struct
This class represents a quaternion type. Quaternions represent a rotation. Typically, they are used for smooth interpolation between two angles, and for avoiding the gimbal lock problem that can occur with euler angles.
Quaternions add a fourth element to the [x, y, z] values that define a vector, resulting in arbitrary 4-D vectors. The following example illustrates how each element of a unit quaternion relates to an axis-angle rotation, where q represents a unit quaternion (x, y, z, w), axis is normalized, and theta is the desired counterclockwise (CCW) rotation around the axis:
- q.x = sin(theta/2) * axis.x
- q.y = sin(theta/2) * axis.y
- q.z = sin(theta/2) * axis.z
- q.w = cos(theta/2)
Usage Example#
The following example creates a quaternion for node rotation: 60 degrees per second along Z axis.
// AppWorldLogic.cs file
public override bool Update()
{
/* ... */
// get delta time value
float delta_time = Game.IFps;
// create quat for 60 degrees per second rotation along Z axis
quat rotation_delta = new quat(0.0f, 0.0f, 1.0f, 60 * delta_time);
// rotate the node
node.WorldRotate(rotation_delta);
/* ... */
}In the example above, the quaternion was initialized by using four values: 3 axis components (x,y,z) and angle (w component of the quaternion). 1 value of the Z axis component shows that the rotation will be performed along Z axis.
See Also#
- An article on Quaternions and Spatial Rotation on Wikipedia.
- A video tutorial on moving and rotating the node by using quaternion (C++)
quat Class
Members
quat ( ) #
Default constructor. Produces an identity quaternion (0.0, 0.0, 0.0, 1.0).quat ( quat q ) #
Constructor. Initializes the quaternion by copying a given source quaternion.Arguments
- quat q - Source quaternion.
quat ( vec3 axis, float angle ) #
Constructor. Initializes the quaternion using given rotation axis and angle.Arguments
- vec3 axis - Rotation axis.
- float angle - Rotation angle, in degrees.
quat ( float angle_x, float angle_y, float angle_z ) #
Constructor. Initializes the quaternion using given angles for each axis.Arguments
- float angle_x - Rotation angle along the X axis, in degrees.
- float angle_y - Rotation angle along the Y axis, in degrees.
- float angle_z - Rotation angle along the Z axis, in degrees.
quat ( vec3 col0, vec3 col1, vec3 col2 ) #
Constructor. Initializes the quaternion using three given matrix columns represented by vec3 vectors.Arguments
quat ( ) #
Constructor. Initializes the quaternion.quat ( mat4 m ) #
Constructor. Initializes the quaternion using a given mat4 source matrix (4x4).Arguments
- mat4 m - Source matrix (4x4).
quat ( dmat4 m ) #
Constructor. Initializes the quaternion using a given dmat4 source matrix (3x4).Arguments
- dmat4 m - Source matrix (3x4).
quat ( float[] q ) #
Constructor. Initializes the vector using a given pointer to the quaternion.Arguments
- float[] q - Pointer to the quaternion.
quat Normalize ( ) #
Returns normalized quaternion.Return value
Normalized quaternion.quat NormalizeValid ( ) #
Normalizes a quaternion, makes its magnitude equal to 1. When normalized, a quaternion keeps the same direction but its length is equal to 1. Check for the zero quaternion is performed: if the argument is a zero quaternion, then a zero quaternion is returned.Return value
Normalized quaternion.quat NormalizeFast ( ) #
Returns normalized quaternion, calculated using the fast inverse square root algorithm.Return value
Normalized quaternion.quat NormalizeValidFast ( ) #
Returns normalized quaternion, calculated using the fast inverse square root algorithm. Check for the zero quaternion is performed: if the argument is a zero quaternion, then a zero quaternion is returned.Return value
Normalized quaternion.float & Operator[] ( int i ) #
Performs array access to the quaternion item reference by using given item index.Arguments
- int i - Quaternion item index.
Return value
Quaternion item reference.float Operator[] ( int i ) #
Performs array access to the quaternion item by using given item index.Arguments
- int i - Quaternion item index.