This is a demo for 3d-Terrain collision. The model itself as exported from Maya and is loaded into a AABB-based Bounding Volume Hierarchy which divides all the triangles. Collision is handled by testing the Sphere against the Hierarchy until leaf nodes are found. Sphere-Triangle intersection is performed with specific checking if Sphere is touching edge or corner of Triangle. Special edge normals are used in these cases since they related to locations where multiple triangles meet.
I wrote a Maya Exporter Plugin that helps get this data from the Mesh.