RenderingServer.viewport_get_measured_render_time_gpu always return 0

[lemtea8]

Godot version

4.0.1-stable

System information

Kubuntu, Forward+/Mobile, GTX 1050

Issue description

I tried to use the code to measure cpu/gpu time, but these method always return 0.

var viewport_rid = get_tree().root.get_viewport_rid()
var duration = RenderingServer.viewport_get_measured_render_time_gpu(viewport_rid)
print(duration)

Steps to reproduce

Download the MRP and run.

Minimal reproduction project

tmp.zip

[Calinou]

You need to enable time measurements first by calling RenderingServer.viewport_set_measure_render_time(get_tree().root.get_viewport_rid(), true) in _ready(). See https://github.com/godotengine/godot-benchmarks for a working example.

We should probably add a project setting to do this this automatically when you need to use time measurements.

You can then get CPU time spent on rendering the last frame using RenderingServer.viewport_get_measured_render_time_cpu(get_tree().root.get_viewport_rid()) + RenderingServer.get_frame_setup_time_cpu(), and GPU time using RenderingServer.viewport_get_measured_render_time_gpu(get_tree().root.get_viewport_rid()). Both of these calls should be performed in _process() to reflect the last frame's rendering as closely as possible.

Testing project: test_measure_render_time.zip

[lemtea8]

Thanks! Adding this option to project settings would be wonderful.

Also I think this is worth documenting, as https://docs.godotengine.org/en/stable/classes/class_renderingserver.html#class-renderingserver-method-viewport-get-measured-render-time-cpu didn't have a description yet.