Scene-Viewer-Preview rendering differences to Scene Viewer

[hybridherbst]

Description

https://vr.google.com/scene-viewer-preview has a transparency rendering issue that is not present in SceneViewer itself, making testing models before going to device harder.

Three issues here:

1. transparency ordering with background seems to be broken, sometimes transparent planes render in front of / behind the background. My guess is that the floor plane's pivot is in the center and thus the floor plane is rendered right between the planes.

2. objects with MASK mode render in a weird, partially masked/partially cutoff way. Looks correct on SceneViewer (top part is cut off):
   Scene-Viewer-Preview:
   

Expected:

3. using a texture with alpha channel and an emissive color does not work in SceneViewer (see 2nd from the left in the above pictures - expected to render white with transparency gradient, actually ignores the white emission)

PS: I find so many issues with SceneViewer I'd really like to have a proper place to report them, I feel both thankful and sorry for the model-viewer team playing the relay here...

@tpsiaki I guess

Live Demo

drop this file in above preview link
Root-TransparencySorting.zip

see last model here for SceneViewer / model viewer (note model-viewer is also broken )
https://glitch.com/edit/#!/spice-water-dormouse