### Rainflow

Gradient flow example using bilinear interpolation of matrix map of Earth altitudes.

For this example, I computed the gravitational force field from a gradient of a 2-D potential energy function, in this case a bilinearly interpolated matrix map of average altitudes of the Earth at every degree (a 180-by-360 dataset).

This global elevation dataset is included with Matlab and is available by running “Load topo”. Their doc page references National Geophysical Data Center, NOAA US Department of Commerce under data announcement 88-MGG-02:

http://www.ngdc.noaa.gov/mgg/global/etopo5.HTML

I used the physics engine from the open-source HTML5 game dev kit (built using d3) that I’ve been working on, available on Github at:

http://github.com/gameprez/gpdk