the new Leadwerks engine supports it that you make your whole world in 1 mesh. Remember? Polygons don't lower the FPS, it's the amount of meshes that does it, as the GPU renderer has to start from beginning on each mesh.
No engine can do that unless you're entire "world" only uses one texture. It's not meshes that lower the FPS, it's state changes, and no matter how the engine dresses it up, if you use more than one texture, it's binding textures between rendering objects. And textures are just one of the state changes. There are many more.