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Notes on Rotation

Article by gemberkoekje, taken from the old reference section.


Rotation is set in radians. Zero rad vector is equivalent to (1, 0) vector in screen coordinates. In other words it is a horizontal line pointing from left to right.

Positive rotation is set in clockwise direction. If vector origin was in the center of the screen, then 1 rad would point to the bottom right corner of the screen.


Set angular velocity changes object rotation value over time. Setting positive value make object rotate clockwise.

By default object starts with zero rotation angle which points horizontally from left to right. As object rotates a full circle its rotation angle value will not reset to zero. Instead it will continue to grow in positive or negative direction according to angular velocity value.

Thus after one full circle the object rotation value will satisfy the condition:

orxMath_Abs(orxObject_GetRotation(obj)) >= orxMATH_KF_2_PI

orxObject_GetWorldRotation and orxObject_GetRotation

Returns current object rotation value in radians. The value returned can be any floating value.

See orxObject_SetRotation for coordinate system reference. See orxObject_SetAngularVelocity for discussion of continuous rotation.

en/tutorials/object_rotation_notes.txt · Last modified: 2018/02/14 04:46 (5 weeks ago) by iarwain