Draw order

Babylon draws opaque meshes in the order they were created. Nothing looks wrong that way, because the depth buffer sorts out who is in front, but every pixel of a far thing is shaded before a near thing covers it. A sky made first is shaded across the whole view and then painted over by the land.

<tosi-b3d> draws opaque meshes nearest first, and the sky last, so a covered pixel is rejected by depth before its shader runs. The picture is the same; the saving is whatever was hidden. On a phone or headset GPU that is a large part of a frame, and on a desktop tile renderer it is close to nothing.

Blended meshes are untouched: they are still drawn after the opaque ones, far to near.

To put Babylon's own order back (by material), call scene.setRenderingOrder(0) after the scene is ready. A sky of your own that is pinned to the camera must set infiniteDistance, or it sorts as the nearest thing and is drawn first.

import { nearFirst } from 'tosijs-3d'
// A render target of your own does not inherit the scene's order.
target.setRenderingOrder(0, nearFirst(scene), nearFirst(scene))