Hello! My level is currently one big enclosed room with metallic walls which makes some things reflect onto them. Without reflection spheres there are some artifacts which I want to resolve. I have decided to use reflection spheres in order to do that. Now I have a question regarding their placement. Performance-wise and generally speaking what is a better practice: place one big reflection sphere that covers the whole level or place individual spheres for each wall and allow them to overlap?
Bump. Still need this 
Box reflection for the whole level. That is supposed to function as a fallback for when smaller spheres aren’t setup.
As far as placement, it captures a sphere around its center. So in a rectangular room you need 2 spheres in the same points you would place the centers of an ellipse that covers all 4 corners of the map, and a square one or another sphere to cover the center portion.
In a square room. One sphere placed at it’s center will do.
Reflections will almost always be inaccurate. Obviously the mirror or metal wall you are looking at reflects differently based on the angle you look. Like a mirror in essence…
doing that is possible, just like mirrors are possible, but it is much more expensive to run since it’s basically rendering a whole scene for every single mirror.
POTENTIALLY, you could make a special material with an exposed texture parameters to inject your own reflection, and create a system that localized the texture and uses whatever you decide to capture locally to the player.
the problems with that are
- capturing a sphere image.
- doing the math to go from sphere capture to reflection plane,
and/or - capturing a 2d shot accurately.
Something like inverse of player camera @ bounce location pushed back a decent distance equal to the the player distance from the surface plus whatever size the surface is (an offset you adjust manually?) May do the trick. At least for 1 object.
You’ll likely still have issues with that - because your view can be away enough from the surface to provide no reflection data that is relevant.
You can sort of mirror (pun totally intended) how the planar Reflections do it.
if you are brainy enough, there’s always a good GPU gems article about this sort of stuff.
Second this one reflection sphere in the middle of the map should do the trick however have you had a look at the box reflection capture actor ?