I am new to Ventuz, so please forgive me if what I'm asking is totally obvious to everyone but me...
I am trying to alpha blend two textured planes which partially overlap. The planes are imported from *.obj files containing vertices and texture coordinates, but no material specification.
I'm adding textures (in this primitive example, a red one and a green one, respectively). Then, I add an alpha value material stage with an alpha gradient. My expectation would be that the red texture smoothly fades into the green texture (BTW, the geometry containiung the red texture is slightly in the foreground). In reality and contrary to what I would expect, though, the red texture fades into the black background:

Two narrow down the reason for this and possibly find an explanation by myself, I added two rectangles manually, made the exact same settings and the result is a smooth fade, as expected:

This might be a bug but I much rather think that I made some mistakes not obvious to me. Could someone please help me? Thanks in advance.
Kind regards
Max