Stuttering when mouse moves from one control to another in editor

CedNaru commented 1 month ago

Tested versions

Godot 4.3

System information

Windows 10 - RTX 3070 - Forward+ renderer - latest Nvidia drivers installed

Issue description

This issue seems to only happen using Forward+ and the single/multi window option has no effect on it. I noticed that when I move my mouse over a lot of UI elements, the editor starts to stutter, which makes it harder to efficiently aim with the mouse. Somehow hovering over only a few elements in a short time doesn't seem to have any effect, but it feels like there is some "threshold" that suddenly create micro freezes when reached. It seems to be totally independent of the project's content, even an empty causes the issues. Occasionally, that stutter results in an occasional single frame being rendered "dimmer" or even entirely black.

I tried to record the stutter in a video, but somehow the act of recording my screen magically makes the issue go away, and it comes back the moment I stop.

It feels like a typical rendering issue related to GPU drivers and such, but so far only Godot displays this kind of behavior on my computer.

Note that I can't see any spike in CPU or GPU usage when having this issue.

Steps to reproduce

Create an empty project with Forward+ renderer
Open the project in editor
Quickly move the mouse back and forth between several UI elements. (moving between a major part of the UI, like main screen and inspector, seems to make the effect even worse)

Minimal reproduction project (MRP)

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matheusmdx commented 1 month ago

I wasn't able to reproduce this issue, probably nvidia related.

Godot v4.3.stable - Windows 10.0.19045 - Vulkan (Forward+) - dedicated AMD Radeon RX 580 2048SP (Advanced Micro Devices, Inc.; 31.0.21916.2) - AMD Ryzen 5 3600 6-Core Processor (12 Threads)

CedNaru commented 1 month ago

I did a bit more digging, and I managed to find the cause of it: Nvidia G-Sync. I have a 144hz monitor compatible with this feature. If I disable it, the stuttering is completely gone. It seems that somehow the Godot Vulkan renderer has a weird behaviour with whatever G-Sync does to synchronize the framerate with the monitor.

CedNaru commented 1 month ago

I went further. Because this is about a feature mechanism related to variable framerate, I tried to enable the Update continuously feature in the Godot editor. The issue goes away as well, even if I keep G-Sync enable.

I feel like G-Sync doesn't do well with the editor having an inconsistent fresh rate when Update continuously is off. Probably, a redraw or similar is queried by the editor UI whenever I hover my mouse over a Control, which makes the editor constantly going back and forth between being updated or paused.

godotengine / godot