High baseline energy impact on iOS when a Control node is present on screen (even if empty)

[PabloNeirotti]

Godot version

v4.1.beta1.official [828ec2c]

System information

iPhone 13 Pro Max - iOS 16.3.1

Issue description

Running the project on my iPhone, Xcode Debug shows a high energy consumption on Godot the moment there is one GUI control, such as a Panel, even if it's empty and no code is running. The GPU goes insane.

Without PanelContainer:

With PanelContainer:

It sounds excessive that just adding a panel apparently shoots up the GPU usage to 80% (mind it's relative) and energy consumption to High. Unless this is an expected overhead and isn't making actually running the game any slower.

Steps to reproduce

Setup a structure like this:

Remove "PanelContainer" for the consumption to go from High to Low.

Minimal reproduction project

N/A

[Calinou]

Did you enable Low Processor Mode in the Project Settings before exporting? If not, high CPU/GPU usage is expected as the engine must redraw 120 times per second on an iPhone 13 Pro/Pro Max and later. (120 Hz mode is enabled by default – you can disable it in the export preset options, but it makes UIs less snappy so it's not recommended.)

Also, consider using the Compatibility rendering method as it's better optimized for mobile devices compared to Forward Mobile.

Rendering a Panel node is fairly expensive compared to a simple image because it draws a polygon with a relatively high amount of points. macOS/iOS are notorious for having performance issues with this due to buffer orphaning, which may still be an issue when using Metal via Vulkan. #77278 should improve performance somewhat, but don't expect massive gains. 2D batching is also currently missing in the Vulkan-based renderers, which means that rendering lots of text will be slow unless using the Compatibility rendering method.

Even with the above points considered, we don't expect Godot to be as efficient as native GUI frameworks when it comes to rendering efficiency. It's just not feasible, given it was never designed with this purpose in mind.

It sounds excessive that just adding a panel apparently shoots up the GPU usage to 80% (mind it's relative) and energy consumption to High.

Note that utilization percentages can be misleading if the GPU isn't running at its highest clock due to power management. Does the profiler let you see the current power state of the GPU, such as its frequency in MHz?

[PabloNeirotti]

Hi Calinou, thank you for your response.

To address your points:

The project is capped at 60 FPS. I'd only allow it to run at 120 FPS if there was a way to keep the cap for 3D rendering and not for 2D rendering/UI. I'll have a look.

I am using what the Godot IDE calls Mobile (I guess this Forward Mobile). Not sure if Compatibility is right for me as shadows are important in my project and seems to have quite a few limitations on this end, but I'll investigate. That said my concern is mostly whether "using GUI elements is bringing my performance down" rather than overall game performance.

But if PanelContainer is already bad for performance, I can try avoiding it by either using a different way of styling it or just write my own code for GUI instead where needed. I don't really need polygon drawing for my UI, as it'll be mostly made up of floating elements, and I already made panels with an "invisible shape" but clearly they still come with a cost associated even then.

It all started with me trying to find the bottlenecks in my game and I kept removing things until only UI was left and I couldn't understand why energy performance was being hit so badly. I'll focus on the UI first then.

I guess we can close this as this behavior is expected, right?

Either way, thank you for your response and for sharing that PR, I'll keep an eye on that.

[Calinou]

But if PanelContainer is already bad for performance, I can try avoiding it by either using a different way of styling it or just write my own code for GUI instead where needed. I don't really need polygon drawing for my UI, as it'll be mostly made up of floating elements, and I already made panels with an "invisible shape" but clearly they still come with a cost associated even then.

You can use a StyleBoxTexture in the theme overrides so that it draws a nine-patch sprite instead of a polygon. This should be slightly faster on average.

[Zireael07]

Small nit: Can you edit issue title to call out iOS/Apple? This keeps coming up in my feed and I keep thinking it's general mobile, or Android specific... and it's NOT.

[PabloNeirotti]

Small nit: Can you edit issue title to call out iOS/Apple? This keeps coming up in my feed and I keep thinking it's general mobile, or Android specific... and it's NOT.

Done

[clayjohn]

@PabloNeirotti Can you compare using a single PanelContainer to having a single Sprite with a texture?

Without a full understanding of how Apple computes energy impact, it is hard to say whether this is expected. Drawing a single element, even if it contains a lot of polygons should be very fast and shouldn't stress the mobile GPU much. That being said, panels do contain a lot of very small/thin triangles which are bad for mobile GPUs in general. Comparing to a sprite would help us identify whether this is a) expected behaviour, b) an issue specific to panels, or c) a rendering issue

[Calinou]

You could also try creating a custom StyleBoxFlat for the PanelContainer with the corner radii set to 0, which requires fewer polygons. You could also try leaving the rounded corners but disabling antialiasing on the StyleBoxFlat, which reduces polygon count. Lastly, try keeping rounded corners and antialiasing but reduce the corner detail to 1 or 2.

[PabloNeirotti]

I just tested your suggestions, and here are the results:

StyleBoxFlat

Setup like this:

Measures like this:

I tried leaving antialiasing on as well, but got the same result.

Single Sprite with texture

Setup like this:

Measures like this:

Bonus: Using a button

Setup like this:

Measures like this:

---

I assumed buttons would be just as problematic (since they use polygons too, isn't that so?) but actually the energy impact is the same as having a Sprite, or nothing at all as well.

Hope this helps to shed some light into the issue. I guess I can stay away from PanelContainer for now 😄. Let me know if there is anything else I can do.