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build lighting in raytrace mode?

Should I “build lighting” when using ray-tracing?
Because I have a feeling that my reflection are not showing up on my metallic materials even with a reflection probe in the scene?

Ray tracing is (usually at least?) real-time, not baked.

That said if your reflection captures are not using Raytracing and/or your materials are falling back on reflection captures, then building reflection captures May help…

There is also a general fallback for when no reflecrion capture provides a texture I believe. But generally if you are using properly set raytracing reflections those aren’t required. They act as a fallback for when raytracing is disabled if you build for it.

and I guess raytrace reflection is only enabled in the camera?

From docs:

And
https://docs.unrealengine.com/en-US/…ngs/index.html

The settings are sprinkled around. Search for reflection on that page and go enable the relative result.

The important part is this one, and you can control those settings via a post process volume:

For every material and pixel, that have a roughness lower than what is set in “Max Roughness” will use raytraced reflections, materials/pixels with roughness above that will use reflection captures. It´s for performance reasons, and noise reduction, that usually comes with very rough materials and low samples for raytraced reflections.