Our goal was to explore a way to draw big trees and still have the ability to zoom and scroll at interactive speeds. The viewer automatically collapses and expands nodes based on the available screen space. As you zoom in, collapsed nodes will expand to show its children. The application also has an overview window to show the location of the current view in the larger tree. You can quickly jump to specific clades by clicking on internal nodes in the main or overview window.
There is a (preliminary) preview of the new web-based implementation here here
Download the source code at github
The initial prototype is a standalone version written in cross-platform C++ and OpenGL. See more details here. Note that this version is no longer being actively developed.