How to make glass not affect light rays?

[Alex_M]

Is it possible to do the following - I've got a window comprised of 2 or 3 glass panes. I want them to reflect and refract as usual but I don't want the light rays to be affected when they pass through the glass panes. I found that the more complex the glass and the more glass objects the light has to pass through, the slower the rendering is in interior scenes. I don't care if the stuff behind the glass receive proper darker shadows or not, though it would be nice if that happened.

In the scene in particular that I'm rendering if I hide the glass in the window the rendering proceeds 2 times faster. I know that I could render the scene with the glass panes hidden and then render just the glass panes in a separate pass but I could save some time from doing this.

Thanks!

[Laserschwert]

Just turn off shadow casting for the glass panes.

[Alex_M]

Thanks. This still doesn't yield the same render times as all glass hidden. Here's the results of my simple test:

Glass with everything by default (turned on) in object properties - 30.3 sec
Glass with "cast shadows" turned off - 26.6 sec (12% faster)
Glass objects hidden - 19.2 sec (37% faster)

[Neilg]

Why would the render times be the same? you're rendering a reflection.
if you still think it's because of the light calculation rather than rendering itself you can also set the glass to be invisible to GI in the vray properties.

[Alex_M]

Why would the render times be the same? you're rendering a reflection.

In the rendered test, I rendered a region which did not include the windows.

if you still think it's because of the light calculation rather than rendering itself you can also set the glass to be invisible to GI in the vray properties.

I just tried. This did lower the times a bit more, thanks for the suggestion. But still not the same as no glass. Maybe it's not possible due to the way the render works.