Download

RT reflection not working on certain parts?

Looks like ray traced reflection has no effect on some surfaces.

Below is viewport with all raytracing enabled except transparency (and those wire mesh is masked not transparent)

As you can see the front face is total black for some reason. No GI, No reflection.

It’s black no matter the bounce and the sample amount of rays

Below is path tracing.

It obviously has reflection or GI.

The wire mesh object is actually a thin box that has correct face normal on both sides

I checked several times and there’s nothing suspicious with the object other than it’s from datasmith.

Any idea what’s causing this?

UE4’s implementation of RT… leaves much to be desired. If your using translucent, switch to masked, as translucent is pretty much unusable atm, In fact im not sure how to get it to work at all, instead of just causing transparency to either show up with patches of black or turn into a randomly flickering solid color. For reflections you may want this: r.RayTracing.Reflections.ReflectionCaptures 1 (There is no reason it should be off by default, it stops reflections from showing up as black when hitting a reflective surface on the final bounce/error)

Something is off with your fence material, maybe it´s normals are inverted and are facing inwards the fence mesh? Because your raytraced image shows only one layer of fence, while your pathtraced fence has two clearly visible layers. Try to activate two sided material for a test run :slight_smile:
Also check, if the color is a pure black, cuz metal and pure black color input don´t like each other for reflections and will result in a pure black surface. Raise the color to a dark grey or white for a test (any value higher than zero/pure black should work), if your material is a metal. Reason for that is, that for metals, the reflection is driven by the color, the brighter = the more reflective the metal will be, and black simply translates to absolutely zero reflections/lithg in that area. Or your roughness is to high, or a combination of both.

I’ll give a try with “r.RayTracing.Reflections.ReflectionCaptures”

Some lights are actually getting reflected fine even on the same surface and it’s only ignoring bounce of directional lights. I’m sure I’ve set reflection bounce to 2 and only thing that I’m suspecting is the fact that the directional light has to go through transparent skylight glass. (I remember that RT threw some tantrum with skylight and transparency in early days)

I have to agree that something is very off with it. It’s actually reflecting other emissive objects fine on the same surface. It just got cut out of the frame.
Also tried two side material with no luck. the mesh normal is fine.
The albedo is not black so that’s also not a problem.
Maybe I’ll look in to master material to see how roughness got treated.

Well, any of it didn’t fix the problem actually.

I tried few more things and narrowed it down that RT reflection is only ignoring directional light for some reason.

Skylight is reflecting fine. I just turned it off.