Added a quaternion-based "Look At" function #659
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Thanks for contributing! Christophe |
Groovounet
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Groovounet
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As suggested in this feature request this function computes a unit quaternion that describes the rotation between screen coordinates and a given camera orientation specified by a view and up directions. The rotation quatLookAt(target - eye, up) is the inverse of the rotational part of lookAt(eye, center, up) and therefore one has to take the conjugate to compute a view matrix.
Instead of implementing it directly by means of quaternions, I chose to compute the according rotation matrix and then convert it into a quaternion since benchmarks indicated that this is faster than using quaternions only. The handedness of the coordinates is taken into account in the same fashion as in the matrix lookAt.
The test checks if a certain camera configuration produces a unit quaternion and if it is equivalent to the corresponding matrix lookAt.