Legacy Documentation: Version 4.3.0
HandleUtility.CalcLineTranslation
static function CalcLineTranslation(src: Vector2, dest: Vector2, srcPosition: Vector3, constraintDir: Vector3): float;
static float CalcLineTranslation(Vector2 src, Vector2 dest, Vector3 srcPosition, Vector3 constraintDir);
static def CalcLineTranslation(src as Vector2, dest as Vector2, srcPosition as Vector3, constraintDir as Vector3) as float
Parameters

src The source point of the drag.
dest The destination point of the drag.
srcPosition The 3D position the dragged object had at src ray.
constraintDir 3D direction of constrained movement.
Returns
float The distance travelled along constraintDir.
Description

Map a mouse drag onto a movement along a line in 3D space.

Certain types of Handles (such as arrows) involve movement along a line in 3D space. For example, the Transform's position arrows move the object along its local X, Y or Z axis as the mouse is dragged. The CalcLineTranslation function converts the movement of the mouse into constrained movement along a 3D line in the familiar way used by Unity's built-in tools.