[2023] Chroma causes giant black squares to appear on screen

Thanks for the report: Your video was SUPER USEFUL! In the end it wasn't really Chroma's fault, but posting with a video gave us the clues we needed.

4 hours ago, kyori said:

These black squares are quite a common occurrence with players. Previously players advised to turn off bloom to avoid it... but I think this is a technical issue in which we shouldn't have to turn off anything to avoid it.

Would you later post to explain what is or caused this visual bug? 

The black squares are called NAN errors.  Essentially, while rendering the frame, the GPU tries some operation which produces a result that is Not A Number. The GPU then throws up its many hands and puts black there because it has no way of knowing what the result should have been.

There are many potential cases where black squares/NAN errors may appear, it's a very broad sort of problem and simply indicates that we're doing something that is mathematically confusing to the GPU. Tracking them down can be difficult because they are usually dependent on specific visual settings and can even be specific to each hardware generation and vendor. Each will require a case by case analysis, so if you have something else that can reliably cause them appear, feel free to open a different thread with your video and repro clues.

In this particular case, we reproduced the issue as being related to standing in a certain distance away from somebody using the Mios with elemental effects enabled. The info I got back from the graphics engineer working on this is that the Mios has an animation bone with a Scale value of zero; if you remember math class, you cannot divide things by zero, the result is "undefined".