sky is visible between cracks in between ground and street or sidewalk

[kfarr]

Issue: I can see the skybox in between the green grass "ground" and the sidewalk as I approach the intersection Impact: This looks bad Instead: I should not see the sky, instead just see grass and a transition to sidewalk

See B in this screenshot

From this branch of loud bike game: https://github.com/3DStreet/loud-bicycle-game/tree/side-streets

[kfarr]

this would be solved by https://github.com/3DStreet/3dstreet/pull/186