Viewer becomes unresponsive when max zoomed out

[leidegre]

Should be reproducible with any empty session, I just opened the viewer and zoomed out to the max, then everything became unresponsive. Using latest version of Chrome in this case.

[leidegre]

Getting the same behavior with Firefox.

[dwilliamson]

Could be some div/0 or nan behaviour in the shaders. I will take a look if I get the time.