Gizmo System

[kpal81xd]

Fixes #2904

Overview

• A reworked port of the gizmo system from the editor to engine extras. Allows for gizmo customisation and modular for easy extension with new gizmos.
• Added an example to showcase translation gizmos.

Translation

Rotation

Scaling

ToDo

Draft 1

• Full test coverage
• JSDocs
• Add shading
• Replace torus for rotate gizmo with custom mesh
• Uniform scaling
• Fix camera facing rotation
• Fixed rotation stuttering at small glancing angles of axes (local rotation)
• Separate intersection and rendering meshes

Draft 2

• Plane to show movement axis lines rather than plane axis
• Change fly to orbit camera (remove distance option)
• Add intersection tolerance as an option
• Sort intersection mesh by depth
• Fixed center box transparency when hovering
• Add starting line for rotation
• Added picker selection in example
• Change rotation to use mouse displacement rather than 3D world position (see https://threejs.org/examples/misc_controls_transform.html)

Possible features

• Add text indicator to show linear or angular distance moved for transformations - useful for fine control

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[mvaligursky]

Approving, great effort, this works really well!