Real (light ray bouncing) Mirrors in UE5

[anonymous_user_0352cc4e]

Hello all,

My Problem

I’m interested in using UE5 to simulate how light would bounce off of an array of mirrors.

I immediately hopped in and started making reflective materials, only to find that while materials don’t truly “reflect” things, as in, this reflection isn’t produced by bouncing rays, but only by using camera views to map what that camera sees onto the object’s texture (Ex. SSR).

After a while that neither varying the kind of light (direct or spot), its type (static or moveable), and its material, I still was unable to produce a set up where a reflective material bounces a beam of light off of itself.

My Setup

I basically have a slightly reflective wall and floor, with a mirror between them, and direct light coming down towards the mirror at a slight angle from above.

• The mirror is circled in red
• I’ve placed an emissive sphere where the light beam should be landing.

• The light source does properly appear in the mirror’s “reflection”.

• Here is the path the light beam should be taking

• Here is what my project looks like in pre-view (it doesn’t change when I start)

• This is the material I’m using for the mirror

My Questions

• How could I go about bouncing the beam off of the mirror onto the wall by only using the rays produced from the direct light?

• Is there a name for what I’m trying to create that I’m just completely oblivious to? I’m new to lighting and game engines.

• If implementing this functionality in UE5 would be cumbersome, are there any engines that automatically come with light bouncing mirrors?

• If this exists, is it a feature only in the Architectural pre-built projects they offer you on start up?

Thank you!!!

[S-Dot]

The only way to get accurate reflections in Unreal is to use ray-tracing hardware at the moment. It needs to be activated in your project settings.

Reflections Environment

You need to increase the number of bounces in the reflection settings of your post process volume as well. So here are the steps:

• enable raytracing in the project settings, restart editor
• place a (infinite extend) post process volume in your scene
• enable ray traced reflections in the post process
• increase bounces in the settings of the PPV
• place a reflection sphere actor in the scene. You shouldn’t need to because the reflection is dynamic but it doesn’t hurt to have one in there for less reflective surfaces
• Make sure your light is dynamic or stationary. The sunlight is a directional light. It’s not a spotlight it is like having an infinite amount of spotlights in parallel.
• stay away from emissive light sources for now. Always use light actors.

[anonymous_user_0352cc4e]

Hey, thanks for the response!

I added everything in your list and it still seems to not work.
Is this what you meant by enable ray traced reflections in a global PPV and increase bounces?

I enabled hardware raytracing, and made sure all objects and lights are dynamic. Thanks for your advice!

[S-Dot]

Can you post a screenshot?

[anonymous_user_0352cc4e]

I added a screenshot into the post, I’m guessing its not showing up? I’ve added it below this text as well. Maybe its a markdown thing?

[S-Dot]

I thought a screen shot of your scene. The one in the first post is hard to read.

I would set the number of bounces as low as possible for performance reasons. 5 should work.

Did you set the reflection method to ray tracing? It’s a bit further up in the PPV.
Does your video card allow hardware ray tracing? You got the latest drivers?

[anonymous_user_0352cc4e]

If by reflection method you mean Reflections > Method, I have set that to Lumen.
I have a 1660 Ti and just updated my drivers.

Here’s an image of a similar setup, light does bounce off of the mirror, but I’m trying to get it to project a spot of light onto the wall.

[S-Dot]

You need to set your reflection method to ray traced. Lumen reflections are good for anything other than mirrors or glass.

Make sure in the project settings you have enabled hardware ray tracing.

Fixing Common UE5 Issues! Changes in 5.0

[Biechiwonz]

Have you found a solution to the problem yet？