I am using PhotoScan to reconstruct Maya (archaeological) architectural groups. While PS does great on facades, often the tops of stairs, landings, and the open areas (plazas) between buildings are not constructed. The latter are either grassy or stucco covered. In a couple of cases it did do so however, and I am not sure why. In several cases sparse points are present, but it then does not calculate a dense point cloud or obviously, meshes (or at best just a few small patches).
My question is whether there are better strategies in photographing such areas or perhaps other settings I should use. Or are lawns and such just too featureless to work with?