We came across an unusual bug that actually happened to us twice in different scenarios.
When there are specific surfaces in the scene using refraction, they sometimes seem to obscure the camera and fill the alpha entirely, even though they don’t occupy the space nearby.
This also happens with displacement off. It feels like the refractive surface casts some sort of infinite “death ray” that will obscure the view once the camera passes through it. It can be “fixed” by applying a normal modifier, but the main reason behind is still unresolved.
In this particular file, the problem happens at frame 16. Previews are in the attachement.
It’s much easier to simply open the attached file and check.
Most likely this is caused by open surface having assigned material with refraction. This creates ambiguity with refractive media boundaries and when a camera happens to be close to such surface it thinks that it is inside volumetric media that has infinitely large dimensions. A fix that should help in situations like these has been released in Corona 13.1, you may want to download and install it and see if it helps with your issue.
The issue is indeed caused by “open” geometry with a volumetric material assigned (Material #38). Disabling volumetric absorption fixes the issue immediately (set absorption distance to 0).
If you wish to keep the absorption effect without the black camera glitch, enable the “Thin shell (no inside)” option at the top of the Physical Mtl and use Thin absorption (under Refraction) instead. It is not advised to apply volumetric materials to open geometry (or geometry with no thickness).
In fact, the solution has already come from the engine itself. Your scene has been created before we improved the camera-in-medium algorithm, hence “Use legacy camera in medium” is enabled. If you disable this, everything will render fine, even in Corona 13 (non hotfix).
