There’s no crack in the model where the ceiling (surface) and wall (VaWall) meet. The ceiling’s points were all snapped to the Wall edges.:
Ambient Light Only;
Ambient and Sun shows the issue (it shows up with ambient off also) It’s an issue if the ceiling extends beyond the wall, and if a simple solid object’s corner is placed at the wall’s edge (so it’s not just an issue with VaWalls);
Perspective at Wall/Ceiling Intersection - there’s no crack;
Ortho View at Wall/Ceiling Intersction - there’s no gap;
This is the side-effect of self-shadowing adjustments being made so that objects don’t cast shadows onto themselves… You can try going into Render Mode’s Shadow settings and slide the self-shadowing all the way to the left and if it makes any difference…
I may be able to tune this up a bit, but it is what it is…and just the nature of the beast for “shadow mapping” techniques… At some point, if the shadow is not biased, everything will be in shadow, because all objects are casting shadows onto themselves.
Thanks… Wondering why it’s never cropped up before? I think I’ve had inside corners in previous renderings. Not sure I understand when it’s likely to crop up and when it isn’t.