SbRotation(3)

NAME
SbRotation - The SbRotation class represents a rotation in 3D space.

SYNOPSIS

#include <Inventor/SbRotation.h>

  Public Member Functions
SbRotation (void)
SbRotation (const SbVec3f &axis, const float radians)
SbRotation (const float q[4])
SbRotation (const float q0, const float q1, const float q2, const float q3)
SbRotation (const SbMatrix &m)
SbRotation (const SbVec3f &rotateFrom, const SbVec3f &rotateTo)
const float * getValue (void) const
void getValue (float &q0, float &q1, float &q2, float &q3) const
SbRotation & setValue (const float q0, const float q1, const float q2, const float q3)
void getValue (SbVec3f &axis, float &radians) const
void getValue (SbMatrix &matrix) const
SbRotation & invert (void)
SbRotation inverse (void) const
SbRotation & setValue (const float q[4])
SbRotation & setValue (const SbMatrix &m)
SbRotation & setValue (const SbVec3f &axis, const float radians)
SbRotation & setValue (const SbVec3f &rotateFrom, const SbVec3f &rotateTo)
SbRotation & operator*= (const SbRotation &q)
SbRotation & operator*= (const float s)
float operator[] (int n) const
returns the n'th quaternion of this rotation
SbBool equals (const SbRotation &r, float tolerance) const
void multVec (const SbVec3f &src, SbVec3f &dst) const
void scaleAngle (const float scaleFactor)
SbString toString () const
SbBool fromString (const SbString &str)
void print (FILE *fp) const

  Static Public Member Functions
static SbRotation slerp (const SbRotation &rot0, const SbRotation &rot1, float t)
static SbRotation identity (void)

  Related Functions
(Note that these are not member functions.)
int operator== (const SbRotation &q1, const SbRotation &q2)
int operator!= (const SbRotation &q1, const SbRotation &q2)
SbRotation operator* (const SbRotation &q1, const SbRotation &q2)
SbRotation slerp (const SbRotation &rot0, const SbRotation &rot1, float t)

Detailed Description

The SbRotation class represents a rotation in 3D space. SbRotation is used extensively throughout the Coin library.

An SbRotation is stored internally as a quaternion for speed and storage reasons, but inquiries can be done to get and set axis and angle values for convenience.

Note that there is one very common mistake that is easy to make when setting the value of an SbRotation, and that is to inadvertently use the wrong SbRotation constructor. This example should clarify the problem:

SbRotation rotation(0, 0, 1, 1.5707963f);

The programmer clearly tries to set a PI/2 rotation around the Z axis, but this will fail, as the SbRotation constructor invoked above is the one that takes as arguments the 4 floats of a quaternion. What the programmer almost certainly wanted to do was to use the SbRotation constructor that takes a rotation vector and a rotation angle, which is invoked like this:

SbRotation rotation(SbVec3f(0, 0, 1), 1.5707963f);

Another common problem is to set the rotation value to exactly 0.0, while wanting to store just the information about a rotation angle: rotations are internally handled as quaternions, and when converting from an angle and a rotation value to a quaternion representation, the information about the angle 'gets lost' if there is no actual rotation.

See also
    SbMatrix

Constructor & Destructor Documentation

  SbRotation::SbRotation (void)
The default constructor just initializes a valid rotation. The actual value is unspecified, and you should not depend on it.

  SbRotation::SbRotation (const SbVec3f & axis, const float radians)
Construct a new SbRotation object initialized with the given axis-of-rotation and rotation angle.

  SbRotation::SbRotation (const float q[4])
Construct a new SbRotation object initialized with the given quaternion components.

The array must be ordered as follows:

q[0] = x, q[1] = y, q[2] = z and q[3] = w, where the quaternion is specified by q = w + xi + yj + zk.

  SbRotation::SbRotation (const float q0, const float q1, const float q2, const float q3)
Construct a new SbRotation object initialized with the given quaternion components.

  SbRotation::SbRotation (const SbMatrix & m)
Construct a new SbRotation object initialized with the given rotation matrix.

  SbRotation::SbRotation (const SbVec3f & rotateFrom, const SbVec3f & rotateTo)
Construct a rotation which is the minimum rotation necessary to make vector rotateFrom point in the direction of vector rotateTo.

Example:

#include <Inventor/SbRotation.h>
#include <Inventor/SbVec3f.h>
#include <cstdio>
int
main(void)
{
  SbVec3f from(10, 0, 0);
  SbVec3f to(0, 10, 0);
  SbRotation rot(from, to);
  SbVec3f axis;
  float angle;
  rot.getValue(axis, angle);
  axis.print(stdout);
  printf("  angle==%f, angle);
  return 0;
}

Member Function Documentation

  const float * SbRotation::getValue (void) const
Return pointer to an array with the rotation expressed as four quaternion values.

See also
    setValue().

  void SbRotation::getValue (float & q0, float & q1, float & q2, float & q3) const
Return the four quaternion components representing the rotation.

See also
    setValue().

  SbRotation & SbRotation::setValue (const float q0, const float q1, const float q2, const float q3)
Set the rotation.

See also
    getValue().

  void SbRotation::getValue (SbVec3f & axis, float & radians) const
Return the rotation in the form of an axis-of-rotation and a rotation angle.

See also
    setValue().

  void SbRotation::getValue (SbMatrix & matrix) const
Return this rotation in the form of a matrix.

See also
    setValue().

  SbRotation & SbRotation::invert (void)
Invert the rotation. Returns reference to self.

See also
    inverse()

  SbRotation SbRotation::inverse (void) const
Non-destructively inverses the rotation and returns the result.

See also
    invert()

  SbRotation & SbRotation::setValue (const float q[4])
Reset the rotation by the four quaternions in the array.

See also
    getValue().

  SbRotation & SbRotation::setValue (const SbMatrix & m)
Set the rotation from the components of the given matrix. Returns reference to self.

See also
    getValue().

  SbRotation & SbRotation::setValue (const SbVec3f & axis, const float radians)
Reset rotation with the given axis-of-rotation and rotation angle. Returns reference to self.

Make sure axis is not the null vector when calling this method.

See also
    getValue().

  SbRotation & SbRotation::setValue (const SbVec3f & rotateFrom, const SbVec3f & rotateTo)
Construct a rotation which is the minimum rotation necessary to make vector rotateFrom point in the direction of vector rotateTo.

Returns reference to self.

See SbRotation constructor with corresponding input arguments for a simple code example.

See also
    getValue().

  SbRotation & SbRotation::operator*= (const SbRotation & q)
Multiplies the quaternions.

Note that order is important when combining quaternions with the multiplication operator.

  SbRotation & SbRotation::operator*= (const float s)
Multiplies components of quaternion with scalar value s. Returns reference to self.

  SbBool SbRotation::equals (const SbRotation & r, float tolerance) const
Check the internal quaternion representation vectors for equality within the given tolerance.

  void SbRotation::multVec (const SbVec3f & src, SbVec3f & dst) const
Rotate the src vector and put the result in dst.

It is safe to let src and dst be the same SbVec3f instance.

  void SbRotation::scaleAngle (const float scaleFactor)
Scale the angle of rotation by scaleFactor.

  SbRotation slerp (const SbRotation & rot0, const SbRotation & rot1, float t) [static]
Interpolates along the shortest path between the two rotation positions (from rot0 to rot1).

Returns the SbRotation which will rotate rot0 the given part t of the spherical distance towards rot1, where t=0 will yield rot0 and t=1 will yield rot1.

t should be in the interval [0, 1].

  SbRotation SbRotation::identity (void) [static]
Returns an identity rotation.

  SbString SbRotation::toString () const
Return a string representation of this object

  SbBool SbRotation::fromString (const SbString & str)
Convert from a string representation, return whether this is a valid conversion

  void SbRotation::print (FILE * fp) const
Dump the state of this object to the fp file stream. Only works in debug version of library, method does nothing in an optimized build.

Friends And Related Function Documentation

  int operator== (const SbRotation & q1, const SbRotation & q2) [related]
Check if the two rotations are equal.

See also
    equals().

  int operator!= (const SbRotation & q1, const SbRotation & q2) [related]
Check if the two rotations are not equal.

See also
    equals().

  SbRotation operator* (const SbRotation & q1, const SbRotation & q2) [related]
Multiplies the two rotations and returns the result.

Note that order is important when combining quaternions with the multiplication operator.

  SbRotation slerp (const SbRotation & rot0, const SbRotation & rot1, float t) [related]
Interpolates along the shortest path between the two rotation positions (from rot0 to rot1).

Returns the SbRotation which will rotate rot0 the given part t of the spherical distance towards rot1, where t=0 will yield rot0 and t=1 will yield rot1.

t should be in the interval [0, 1].

Author

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