Compute proper mesh bounds

[David Williams]

Mesh bounds are currently hardcoded:

// FIXME - Get proper bounds
renderingMesh.bounds = new Bounds(new Vector3(0.0f, 0.0f, 0.0f), new Vector3(500.0f, 500.0f, 500.0f));

This should be fixed.

[David Williams]

This has been improved and is now OK for version 1.0. Further improvements can be made in the future (removing the hard-coded size).