filament transparent shader not transparent at certain view angle

[1939938853]

Hello,

I'm trying to use filament based visualizer in Open3D. When doing transparent rendering, at a certain angle it is not transparent.

How to solve it?

Thank you!

view 1: transparent case.

view 2: just small view angle change, it becomes not transparent.

Here is the shader I'm using:
https://github.com/isl-org/Open3D/blob/master/cpp/open3d/visualization/gui/Materials/defaultLitTransparency.mat