Create ‹three-view› element

[olange]

Factor out the rendering parts from the ‹three-app› basic container, so to allow:

• creating multiple views of the same scene, with different point of views (that is, different cameras);
• or running multiple animations next to- or on top of each other — such as a top-down perspective mini-map in a point-and-shoot game, along the main 3D scene, in first-person perspective.

See also

• Create ‹three-app› basic container and view #2 Create ‹three-app› basic container and view