I use to use sections to see the effect of the sun inside the house, how far it enter in some days and hours.
The last few times I tried it, the shadows was wrong.
The sun was entering from the “missing roof” of the section.
Do I do something wrong?
Do I forget a step?
Please advice
Have a look at this tread in this forum “Open floor plan model”.
Thank you Piil60 but it is not working.
Some of my buildings are more then one floor.
I just do not understand. It use to work.
Unfortunately I don’t know what exactly is wrong, but if you upload some pict. or the model,
somebody here can probably give better advise.
Maybe you also have some more information:
Did you change anything before this started? Etc.
Cheers
One way is to create a face a tiny distance behind the cutting plane.
• Paint the face with a transparent PNG material.
• Set the properties of the face in Entity Info to cast shadows.
• Hide the edges of the face if needed.
Here’s the result; the back faces of the walls were simply painted black.
There is also the old trick of painting only the back face of the roof surface with a transparent PNG material so that the roof remains opaque when viewed from below. The trick with a transparent PNG works only within SketchUp - in rendering applications generally, if a surface is invisible it won’t cast a shadow either.
Anssi
Ok. I had the same problem. What I do is turn off the view shadows in sketch up. You will have plenty of light, and with a little photoshop work with the levels, you can get a very good image. I will try and attach one that I did so you can view it.
If you want shadows coming in form open door and windows, simply add spot lights just outside the window. Position them just below the window so no light spills over and point them so they are shining through the window or opening. 
When I used a simple model like you did, it works without problems.
This model i attached as upload it does not work for me and I can’t understand why.
I import this model from revit if it change anything
Please advice
