Did you know you can add a custom view mode to the buffer visualizations in #UnrealEngine4 ?
In the project's DefaultEngine.ini you can add a few lines to add any Post Process material you've made. I used this for easily checking Ray Tracing cost. (1/3)
Make a material you want to use and add it to the DefaultEngine.ini like so:
RayTracingCost=(Material="/Game/Developers/keoken16/M_PP_RTXCost.M_PP_RTXCost", Name=LOCTEXT("RTCostMat", "Ray Tracing Cost"))
If anyone's curious, this is a part of the material that checks the roughness against the reflection MaxRoughness. Close to 0 gets RT reflections so is green. Close to the MaxRoughness is rougher (more expensive) and colors red. Everything above MaxRoughness (no RT) is grey.
The final image: