Reflections - Help me understand

Development Rendering
, , , ,
1

Hey guys, this is something I need help wrapping my head around.

Here’s an image of a quick scene. There’s a sphere reflection capture in the scene on the first image. The left chair is Static, the right moveable. Lighting has been baked.

http://puu.sh/eD4sD/0bbc546d81.jpg

For the second image I’ve deleted the sphere. Why is it that the reflections on the wall don’t change, but the chair does? Again, the left chair is Static, the right moveable. Lighting has been baked. All of my walls are also static with both images.

http://puu.sh/eD4Bf/db34866727.jpg

I can see that there are very subtle differences, but without a reflection sphere, shouldn’t my scene not reflect anything at all? I also have Screen Space Reflections turned off in my Global Post Processing.

2

Apparently, regardless of having SSR enabaled or not in my Post Processing, it’s still turned on. Having reduced it’s intensity to ‘0’, now I’m able to turn it off. This seems to be why my walls hadn’t changed. The SSR was doing a pretty **** good job without reflection spheres it seems.

With SSR: http://puu.sh/eD6ZP/3a2ea6297b.jpg

Without SSR: http://puu.sh/eD75n/204853655d.jpg

3

Seems SSR has to be set to ‘0’ instead of just unchecking the box for intensity.

With SSR:

http://puu.sh/eD75n/204853655d.jpg

Without SSR:

http://puu.sh/eD6ZP/3a2ea6297b.jpg

Begs the question, what use do I have for reflection spheres if SSR is pretty accurate, or is it just a matter of performance?

4

Some other things I’ve noticed too:

Distance plays a huge factor, the close I go, the less of the reflection I can see. I’m led to believe this may be due to it being ‘Screen Space’, so it only reflects what I can see on screen:

http://puu.sh/eD9ln/ab101c851e.jpg

Is there a way to increase the overall quality of reflection spheres, or would I need to bake cube maps if I want this to be ‘perfect’?

5

Hey LWNorman -

There is an excellent write up in our documentation about the reflection environment which can be found here, Reflections Captures in Unreal Engine | Unreal Engine Documentation

It will answer most of your questions and tell you the limitations for reflections that currently exist. Screen Space Reflections are typically used to help ground an object only and not to be full reflections for a full real time reflection you would need to reference the Scene Capture 2D components, the Reflections Map in Content Examples is a great reference for the different types of reflections as well, https://docs.unrealengine.com/latest/INT/Resources/ContentExamples/Reflections/index.html

Thank You

Eric Ketchum

6

Thanks Eric. I think after stewing over this for a few days I wrapped my head around the majority of it. Posting the question itself helped me understand it all too. The UE4 documentation is, as always, fantastic and I’m very grateful for it.

Hopefully this page will help shine a light on the subject when others are as confused as I was. Cheers!