Modifying ofEasyCam to pan/zoom a 2D map

I’ve decided to use openFrameworks to do some modeling and visualization of traffic data (for a project at work). Here’s an initial look at what I’m dealing with – the city of Pasadena, CA, drawn as 14k+ “links” on their road network (never mind the color and stroke weight…):

I’d like to be able to pan and zoom the map. It seems like ofEasyCam would be the easiest way to do this. However, I’d like to avoid stuff like this:

What I want to do is:

  • mouse drags only pan on the x & y axes.
  • zoom in and out (at a controlled rate) by holding down and
  • never rotate the camera off of the current project plane

How do I go about modifying ofEasyCam to bind that behavior to the mouse and those keys?

p.s. If there’s an easier way to achieve this that doesn’t use ofEasyCam I’d love to hear about it.