Planar reflection actor bug

I am not sure if it’ some sort of limitation or what…

I have 1 planar actor and it works perfectly. When I add a 2nd one, the 1st one gets very very blurry. Sometimes it will even lost all his reflective proprieties.
Is there something I’m doing wrong?

If I hide the 2nd actor, the 1st become clear again… Can we not have more than 1 planar actor? I have them placed kinda far away from each other and they’re not facing the same direction.

Hi heartlessphil,

according to current documentation it uses a GLOBAL clip plane, hence ONE for everything.

You can have multiple Planer Reflection Actors, but if you do they need to face the same direction AND need to be on the same height level, otherwise the reflections clip planes might be off.

If you orient them differently the exact artifacts you described may happen. :slight_smile:

Please note that most of this is based interpretation of what is described in documentation here:

Have fun

You are supposed to be able to have multiple planar reflections - at least that’s how I coded it. However, I haven’t done much testing of multiple planar reflections, so it sounds like there’s a bug.

The global clip plane thing doesn’t mean only 1 planar reflection, it means only one clip plane per render of the scene, but planar reflections are separate renders of the scene (from the mirrored camera position).

Hey heartlessphil,

Can you post this on AnswerHub in the Bug Reports section with any details you have to reproduce. I’ll take a look at this on Monday since I don’t have time today to take a look. If you shoot me a PM here on the forums once it’s posted I’ll assign myself and follow up.


Hi Daniel,

doesn’t “global” clip plane mean that there is just one that is shared between each PR-Actor? and if you have multiple such actors that are angled differently that the results may be interpolated and therefore may yield unexpected results or am I misunderstanding things? :slight_smile:

Nope =) It means global to the scene for the current camera render, as in not just one mesh gets clipped by it but the whole scene. Each planar reflection is a different camera render though.

The reason there’s a project setting to support the global clip plane is that it adds a bit of overhead to the base pass vertex shaders, which affects even the main camera render.

Posted on answer hub and made a video.

Hi , is this bug fixed? still getting same problem in ue 4.24.2
its not working on more than one planar reflection.

Running into this issue as well, not a complete blocker for me but would greatly love a fix :smiley:

how can you say its not a complete blocker? just because of this bug i was about to lose my client and project both. i had to switch to offline Rendering engine despite of the project was finished in ue4. i guess this is the problem with real time render engine you cant rely on 100% if you are working on professional quality project or lose your client.

see the post below which i had posted some times ago. i had run into this problem but coudn’t get solution.

Because fortunately for my specific project at this time, it’s not.
I’m using it for lake reflections and don’t necessarily ‘need’ to have more than one.
If I decide to I’ll just have them all at the same height.

I’m sorry to hear you almost lost a client due to this issue. I’m also really surprised to hear they were willing to drop the entire project for table reflections that wouldn’t be 100% accurate.
I wouldn’t go as far to say that you can’t rely on the engine for professional projects. I sounds like you’re coming from an offline rendering background I’m assuming? Working with game engines is definitely a challenge and you’ll always run into bugs and issues and sometimes you’ll have to figure out creative solutions to go around them, which can sometimes be fun. :slight_smile:

i agree, its not a big issue if you did not get into same problem as i have. in game development most of the time one large planar reflection is enough. For interior photo-realistic scene the use of planar reflection can be different.

I can understand you are surprised hearing about droping the project only for reflections because you are in game development where FPS is more important than photo-realism but in archviz photo-realism is the final thing above FPS. and most important client doesn’t care about you are working with realtime render or offline render or your software have limitations when it comes to video content all they care about final video with photo-realistic result delivered on time. may be this reflection is small thing for you but when video is played on big screen in 4k resolution anyone and your client can notice that.

and yes i come from offline render background and i have known unreal engine for very long time and knew it is made for game development thats why i never got onto this but things changed when Epic started promoting unreal engine as archviz development too with their promotional photo-real videos. I believed epic and was really excited but after getting into this problem i came to conclusion for archviz project you cant rely on100% on unreal engine.

and its not only about refection there are other things also when it comes to working on big project it can eat your time just fixing the bug or coming up with creative solutions to fix that and make you miss the deadline and lose your client. it is good for hobbyist otherwise some big company with big programmers team who can quickly fix the bug or come up with creative solutions.

Has anyone picked this up yet? It seems like a real shame to implement this limitation, particularly as raytraced translucency breaks two-sided foliage now too so my fall back of using planar reflections is also not applicable!