background visible throug transparent object in .PNG, should not be... ideas?

[Madmike80]

hi everybody,

im struggling with a problem sometime now, and haven't been able to find a solution myself...

when rendering a car with solid (not-transparent) windshields in .PNG, the render displays no background so we can nicely photoshop it over some background picture. now when the interior is modeled and we want to make the glass transparent, the background is visible trough the glass, witch should not be. it should be transparent with light window color and reflections. as opposed in PNG...

there is an option in the object properties to uncheck "visible to reflection/refraction"... if i could ONLY uncheck visible to refraction, and leave reflection visible, it would be ok. (as it is possible in Vray)

anyone know how to fix this? I've searched object properties, environment settings, material settings and renderer settings but could not find it or overlooked it.

the material i use is an arch&design and mentalray renderer. the lighting is a standard sunlight with HDRI map, environment background is the same HDRI.

don't mind the ultra-reflective paintjob and crappy interior... just for illustration.

thanks in advance for looking in!