Fix rendering bug

[liruilong940607]

fix #111

The get_tile_bin_edges_tensor defined in the bindings is buggy -- tile_bins should be with shape (num_tiles, 2), not (num_intersects, 2).

[liruilong940607]

The above commit fix rendering from

to

But the bottom right corner is still buggy

[liruilong940607]

The above commit fix the rendering to

@vye16 My understanding is this 0.5f is to account for the half pixel size but I'm not sure whether it should be +0.5 or -0.5. Just flipping it makes the bug go away. Let me know if you think the original one is the correct way then the we need to fix it from somewhere else.

[liruilong940607]

All tests pass locally

[vye16]

thanks for the catch, this is super helpful, sorry it was buggy for so long

[vye16]

I'm also not sure, in the original release, it was +0.5, but then in #91 test case, the pixel difference was off by the wrong sign for a single gaussian at the center so flipped it to -0.5. maybe just use +0.5 for now