Section Cut_Sunlight Analysis

Hi all,

I’m trying to make a sunlight analysis of a project in PLAN. I have used the section cut tool and applied shadows.

However, this isn’t actually accurate because the roof of the building isn’t present and is much brighter than it should be (because its behind the section cut line).

Is there a way of making a section cut and retaining any of the elements behind it? Any plugin or script that will make a section cut act as a solid?


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As a Pro user you could consider making two Scene tabs with identical plan views.
Do no use Sections at all, use Layers
One tab would be with the Roof Layer switched ON and one with it OFF.
In Layout link the SKP.
On a page paste a view port for the roof plan [with shadows].
Lock it.
Copy that vp and change its scene the the floor plan [without shadows].
Lock that.
With the Roof plan below the main plan the shadow should show correctly, although the floor plan is visible.
If there are big roof overhangs that might be seen consider having the real roof layer switched off, but a copy of the roof group on another layer with all of its faces painted in a fully transparent but shadow casting material [PNG texture] so you still see the shadow without the roof ?

This simple example SKP [v2013] might help - left hidden lines on so you can see the transparent roof…
It contains the fully transparent but shadow casting material used on the that roof copy…
TransparentRoof.skp (60.9 KB)

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Your question isn’t clear to me.
A section cut takes away part of the model on one side of its plane (as in making it invisible) so it has no influence on the model, even on shadow casting.
If you need the roof to be there to cast shadow, make the roof a group and paint it with transparent *.png material. The roof will then be “see through” but still project its shadow on all that is beneath it.

As an example see in 3D Warehouse: (seach: Wo3Dan+Shadows study)

You can extract the transparant png in this model to apply in your own model.


Thanks so much guys…Really appreciate it. Used Wo3dan transparent png file and stretched it in photoshop.

Painted materials will tile. So a 100% transparent PNG used to paint an ‘invisible’ face only needs to by 1px x 1px in size.

Another thing you could do is select the floor and uncheck “Receive Shadows” in the ModelInfo inspector.

(And/Or also uncheck “Cast Shadows” for all your interior walls ?)

Yet another method:

Create two scenes with shadows, one of the full model, and one of the floor plan on a white background, and overlay the two in LayOut.


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Hi your answer is exactly the answer I was looking for thank you !

However, I cannot seem to apply the same png material that you have put on your model to mine, it does not appear in my material panel.

Could you tell me where I can find a transparent *.png material please ?

Thank you very much !

You could use attached file, credit to @TIG, posted right above my answer marked as solution.
It contains transparent material. Probably just as in my shadows study that you mentioned.

TransparentRoof.skp (60.9 KB)

(My file must be stored somewhere)

Here’s another file with transparent image (left) and an exploded copy giving transparent texture, to sample and use on other faces.

transparent image and rectangle with png.skp (215.0 KB)

You may want to cut and resize the image since you do not need that many pixels to make a full size face transparent.

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