BackBufferCopy rect mode does not improve performance

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1

Godot Version

Godot 3.5.3 gles2

Question

Hello there.
I was messing around with BackBufferCopy to implement shockwaves effects. I created the following scene :
image

That sprite has the shader which uses the SCREEN_TEXTURE. Then i have the main scene create 100 instances of this scene.
My issue is i find no difference using BackBufferCopy viewport mode which copies the entire screen(1024x600) versus using rect mode, no matter the size of the rect. Both tests gives around 5-7 ms, even if i use a rect with size 0x0, making me suspect i did something wrong.

2

I don’t think the size of the screen being copied is going to matter significantly compared to other parts of the rendering