3D Shade Calculator Shading Issue

SAM version 2020.11.29.  Trying to assess the relative impact of module placement on a roof where shading from other roof surfaces will be an issue.  No issues with placing a one module active surface on a roof where there is no shading.  Moving the active surface to a different roof section where some shading can be expected is a disaster.  Suspect I'm missing something obvious.  The 1st shot is the active surface at roof level while the 2nd shot simply changed the active surface Z value from 19.55 to 24.55 essentially clearing the surface from any shading.  Z values are feet.  Expectation was that the 1st shot would show some shading loss in hour 17.  No idea how/why the 2nd shot shows a shading loss at hour 14.

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Hi Graham,

Could you attach a copy of your SAM file with the shading scene so I can investigate?

Best regards,
Paul.

Hi Graham,

Thank you for emailing your file. We are investigating, but for now, it seems that the erroneous shading that appears for some sun angles is caused by intersecting objects in the shading scene. This is a bug that we will try to fix.

To work around this issue, you can try to avoid having any objects in the scene (box, cylinder, roof, tree, active surface) touch each other. For example, if a box represents a building and has a height of 3, its roof should have a z position greater than 3. Also, in your scene, the walkway roof and pool roof touch each other, which seems to cause some shading on the active surface, even when its z position puts it high above the roof where it should not be shaded.

Having objects overlap in the scene makes it possible to more realistically represent what the building looks like, so I realize this not a perfect solution, but I wanted to give you something to work with while we dig into this further.

Best regards,
Paul.

Paul,

Thanks.  Provided a slight separation between the boxes and roofs and appear to be getting good results.  Did not need to separate intersections between roofs.