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Reflections of movable objects won't show up after passing them - UE4

Hi, for some reason when I pass a movable object and can no longer see it, I can also no longer see its reflections on other objects.

Attaching a picture to explain, on the left you can see the question mark icon and its reflection, on the right when i move forward and pass the icon I can no longer see its reflections as well.

It's important for me since I want to see reflections of moving objects in a really big space.

Any ideas how to solve this problem?alt text

Product Version: UE 4.12
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asked Oct 01 '16 at 10:24 PM in Rendering

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I think that you are not seeing the question mark because it is not baked into cubemap and its reflections are being calculated in the screen space(Screen Space Reflections, or SSR shortly). Only objects, that are already present on the screen, can be reflected that way.

There are also planar reflections, but those are designed for flat surfaces.

From here, you have two options. Either make your question mark static and have it baked into the cubemap, or, if you can't allow having it baked, just accept the limitations of SSR. Usually it is quite hard to spot such difference in reflection image during actual play.

If that helped, don't forget to upvote the answer and mark your question as resolved.

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answered Oct 01 '16 at 10:53 PM

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avatar image Volcano-Studios Oct 01 '16 at 11:32 PM

Thank you for your (very) fast answer yeah I can understand that.

However I was wondering if I could use blueprints to hack the system and tell the reflection prob to update each frame, obviously for gaming purposes it wont help since it will take a lot of memory but for cinematic it might work.

avatar image Deathrey Oct 02 '16 at 12:15 AM

It is possible, though it is not as easy as you expect. Reflection probes store no realtime data.

However, there is a SceneCaptureCube, which you can use to capture a cubemap to a RenderTargetCube but, you can't feed it into to a reflection capture actor directly.

What you can do, is to pass that cube render target into material and handle reflections there manually.

Alternative approaches, if they exist, involve coding with modification of the engine, most likely.

avatar image Volcano-Studios Oct 04 '16 at 06:05 PM

Well I tried updating them in realtime and I couldn't do so so I ended up with your second suggestion to use cube render target. The problem is that its a cheat so I have to cheat the roughness as well.

BTW It is important for me not for the question mark but for moving studio lights dynamically around an object with bot metallic and dielectric shaders with different roughness values.

Thank you!

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