Texture blurriness in `SubViewportContainer`

[AdamLearns]

Tested versions

• Reproducible in v4.4.beta1.mono.official [d33da79d3]

System information

macOS Sonoma 14.6.1 (23G93)

Issue description

I see a lot of similar issues that were filed already, but none that seem to still be open that cover the scenario I'm in:

• display/window/stretch/mode is disabled (SubViewportContainer does not scale Viewport properly with CanvasItems project scale mode. #77149, Subviewport rendering different than non-viewport rendering #86975)
• This is on v4.4.beta1 where some of those issues should already have been fixed (Popups (OptionButton, tooltips) placed and scaled wrong when using canvas_items stretch mode or scale factor different from 1.0 (DisplayServer regression) #54030, Blurred embedded subwindows, when content_scale_factor is set on parent Window #71403)
• There are no pop-ups involved (Popups (OptionButton, tooltips) placed and scaled wrong when using canvas_items stretch mode or scale factor different from 1.0 (DisplayServer regression) #54030)

The issue is that a TextureRect inside of a SubViewportContainer looks blurry while a TextureRect outside of that container looks crisp. Same thing with a Sprite2D.

Steps to reproduce

Set up this scene hierarchy:

• Node
  • SubViewportContainer
    • SubViewport
      • TextureRect with size 64, 64
  • CanvasLayer
    • TextureRect with size 64, 64

...and that's it. Even in the editor, it's apparent that the texture in the SubViewportContainer is blurry:

I originally thought this was caused by setting ContentScaleFactor, which is why the minimal repro has buttons to change that. I left the buttons in the repro since it's much more obvious at higher scale factors.

Minimal reproduction project (MRP)

ContentScaleFactorRepro.zip

[matheusmdx]

Tested on 4.3 stable and 4.2.2 stable, both can reproduce the issue

[kleonc]

AFAICT that's not a bug. The original 128x128 texture is rendered into a 64x64 viewport (loosing details), then such downsized/downscaled ViewportTexture is being upscaled, hence the blurriness. OTOH the TextureRect on the right is sampling the original 128x128 texture all the time.

You'd need to render to a 128x128 SubViewport, and then shrink/downscale whatever renders such ViewportTexture.

Related:

• Restructure Viewport size and size_2d_override godot-proposals#6221 (comment)