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!

[Braiz]

Have you checked the "transparency propagates alpha channel", under advanced rendering parameters??

[EquiNOX]

What render engine? I assume Braiz shown how to do it in MR... as for VRay see attachment.

[Braiz]

Well I just assumed it was mental ray, since it was posted in the mental ray section

[Helicase]

I was having the same problem thanks equinox!

[EquiNOX]

Ooops! I should pay more attention on thread group... Well at least I have helped helicase

[Madmike80]

haha, indeed the question was with the MR renderer, i´ve posted the same question back then in march on SMC too, and got the same answer braiz gave about the "transparancy propagates alpha channel" checkbox, wich indeed solved the problem. good to see the thread helped the V-ray users also!