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Reflection plane has "show data" checked by default
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Description

System Information
Operating system: Win 10, 64bit
Graphics card: dual GTX 1080ti

Blender Version
Broken: 2.80, 12da679fa094, master, 2019-06-16

Short description of error
Reflection plane has "show data" checked by default (only needed for debugging), which confuses user thinking it's broken, since other reflection probes don't even have this feature.

This might not technically be a "bug" but at best it's inconsistent. It took me lots of searching before I finally realized why it was happening. I suspect others will be confused too.

Event Timeline

Brecht Van Lommel (brecht) lowered the priority of this task from Needs Triage by Developer to Waiting for Developer to Reproduce.

In the Unreal engine, the "Planar Reflection" object behaves the same. In Unreal the property is called "Show Preview Plane". For Eevee the property should probably at least be renamed to that too, I couldn't come up with a property name that's more idiomatic to Blender than "Show Preview Plane" already is.

In Unreal I appreciate this default, because the first thing I do after I add a planar reflection, is use this "Preview Plane" to start excluding/whitelisting objects. Letting the planar reflection rerender the entire scene as-is is never performant enough. In Eevee performance is not a primary concern, so it is debatable if Eevee should default it to be "on". In Eevee it also doesn't show up in renders, only the viewport. Just like in Unreal, but it has a global "Game View" toggle that also show/hides widgets (etc) which users constantly tend to toggle, so you catch this quicker.


What I've noticed with myself and multiple others that first use reflection planes in Unreal, is that this weird preview plane drives people to look up the documentation which is good. Because in Unreal (and in Eevee) roughness for planar reflections becomes a "reflection opacity" factor as opposed to reflection captures/SSR which interact better with PBR. Using planar reflections without reading this crucial piece of documentation leads to a different category of difficult/confusing visual issues.

Interesting! I didn't know UE4 had it default on as well. But you're right that a "Game View" toggle allows users to see it the correct way, whereas no such toggle exists in Eevee. Hence confusion.

From my perspective it's odd that the standard cubemap reflection previews the same as rendered, yet the plane has "show data" on by default. It really is confusing :S

To clarify, Eevee's reflection plane preview does already conform to the "Display overlays" viewport toggle. But in Unreal the "game view" toggle is bound to "G" by default and its widgets usually are more intrusive so most become very used to toggling it back and forth constantly.
Just to experiment, I bound a shortcut key to the "Display overlays" and noticed I started using it a lot within moments.

The counter argument is that the planar reflections are not necessarily visible if you don't have SSR on and the surface if a big rough.
Also I did enable it by default to comply with unreal's default.

To be honest I'm on the fence here. Because like you said, the other probe types do not display their data by default.

You could say that other probes do not work if lighting is not baked, so in the same way you have to know how to use the planar reflection before seeing the result.

@William Reynish (billreynish) any thought?

@Clément Foucault (fclem) I think this is more of a debug type display option that makes sense to keep off by default.

We could also change the name. "Show Data" doesn't really communicate so well. "Show Preview Plane", as suggested earlier here might be nicer. Or "Show Reflection Preview".