Target
Owner will be projected on the mesh surface of this target;
Be noted that, if the raycast from owner cannot hit on the target mesh, then the owner's position will be unchanged;
Distance
By default, constraint will put the owner's pivot onto the raycast hitpoint, however this could cause the owner to burrow into the target mesh.
The distance value will keep the pivot away from the raycast hitpoint.
For example, the primitive cube is 1 unit length, and pivot at the center. So the distance should be 0.5 unit;
Project
This section contains three part: direction, space, maxDist;
Space: decides the project raycast direction should be in world space or local space;
Direction: the raycast's origin is the owner's pivot, the direction is specified here, in the specified coordinate space;
Max Distance: This is the raycast's max length, (0 means infinite)
