Ray Tracing Debug

1.0 What It Actually Does

If you use RayTracing in your project this is so helpful for you, first of all Debug RayTraced Reflection, very important for RT Projects/Scenes

Raytracing Reflection Debug

Explaining the colors

• Green/Dedicated Rays: Surfaces with low roughness (e.g., polished metal, glass) are prioritized for dedicated ray tracing, resulting in accurate reflections.
• Red/Surface Cache: If visualizing dynamic instances, red often represents static instances, while green shows dynamic instances in the scene. If referring to the reflection view specifically, it often highlights where screen-traced reflections (red/low quality) mix with or fail over to dedicated rays (green/high quality).
• Performance Optimization: Use the CVar r.Lumen.Reflections.MaxRoughnessToTrace to adjust the threshold for which surfaces get dedicated rays in your project, Alternatively, adjust this in your Post Process Volume to trace higher roughness values (e.g., 0.5, 0.6). Be careful: tracing rougher surfaces casts significantly more rays and will heavily impact performance.

Left:

r.Lumen.Reflections.MaxRoughnessToTrace 0.7

r.Lumen.Reflections.MaxRoughnessToTraceForFoliage 1.0

Right:

r.Lumen.Reflections.MaxRoughnessToTrace -1 (PostProcess will override this instead)

r.Lumen.Reflections.MaxRoughnessToTraceForFoliage 0.4

In this case, the debug mode knows what your project is using so it tells you if your RT is actually tracing reflection rays for those values, the moment you update your project settings it tells you of that. It's advised to keep Max Roughness To Trace, as it's performance hungry. Default in UE is 0.4

RT Instances

This shows you the ray tracing instances such as blueprint instances, static meshes...

RT Instance Overlap

Very useful to see if you have meshes overlapping as that'll add more possibility to have artifacts, performance effect.

RT Hit Count

This gives you the hit count of each Primitive Component & its ID, Name

RT Picker

Allows you to hover on triangles, or instances if you have Pick Instances enabled, you'll read on the left side of the screen the data that you need to understand the cost, the count of geo on the viewport directly.