Transparent but still cast shadows?

I am trying to create a “ceiling” in a room that is transparent for the purposes of modeling and viewing the room but still is opaque to lights, sun etc. I’ve tried to get a transparent surface to work and monkeyed around with a horizontal clipping plane below an opaque surface but neiter approach seems to work.
Seems like this ability would be useful for people modeling interior spaces who want to see the effect of windows etc.
Any advice?

Hi Nick,
I thought we could put the surface on a layer turn the layer off, but turn on “Use lights from layers that are off” under render settings but this doesn’t seem to be working in V6.
Maybe another setting I am overlooking.



Hi Roland,
Thanks for trying. This would seem to be a useful feature. With all the rendering-in-viewport options available now it is possible to get a (relatively) realistic view of an interior space. However you need to have a ceiling/roof. But that makes modeling difficult.
I would like the godlike ability to reach through the roof and work on the interior.

Hi Nick - in a viewport display, you should be able to set the walls to use a display mode that has the backface settings to ‘cull back faces’ and point the walls inward. However, in V6 right now, that culling is completely broken, and in V5 it only partly works (shaded faces are not culled) But… if we get that tuned up, you should get what you need in the viewport at least.


OK. Something to look forward to!

Hi Nick- try it in V5 to get an idea - Make a box, Explode it and point all the faces inward (or use a mesh box and Flip it inward. Make a copy of Rendered display mode and edit it so that Backface usage’ uses Cull back faces. Use SetObjectDisplayMode to set that mode on the box faces - is that kind of like what you are after? The shadow problem is still in the way, on my machine at least, but you’ll get the idea.


Hi Pascal,
Well it’s trying to work but not succeeding.
I make a couple of boxes to stand in for furniture then a larger box to represent the building. I put a door way into it so sunlight could get inside.

Then I set the sun to “on”, and did the explode/flip/cull trick on the building. Depending on the orientation of the wall relative to the sun it let me see inside or not:

And I still can’t select the interior objects, the invisible wall selects instead.

The skyight works a bit better, but still not usable:

So like you say, it shows a direction but isn’t usable.

Hi Nick,
In theory this approach should work as I use it in 3dsmax all the time to do just exactly what you are doing or even to not cast shadows. This seems to me to be a bug it should be as simple as using the cast shadows from layers that are off switch.
O well another thing to work around.