Thread Subject: objects with transparency rendered using opengl looks wrong in export

Hi all,
I have been trying to plot some datum points using plot3 to
a figure with a transparent surfaces created using patch and
isosurface.

However, whenever I want to export the figure to png/pdf,
the datum points plotted will look as if it is inside the
surface, even when the point is definitely outside the
object (as confirmed by rotating the object). The datum
points look in front of the transparent object on screen
(expected), but not in the exported pdf/png file. Is it a
known bug, or is there any workaround? Thanks