mrdoob/three.js — pull request #3509 by roissard (2013-05-24 12:15:55+00:00)
Title: WebGLRenderer: Initialize 'z' when adding buffer to object list

The "z" property is used when sorting object list but is was not initialized.

A bug occurs for objects that are first frustum culled and then visible. When they become visible "z" is undefined and sorting acts randomly.