Vulkan: 3D viewport no longer uses nearest-neighbor filtering when Half Resolution is enabled, resulting in a loss of sharpness

[Calinou]

Godot version: Git c3b23f0, but applies all the way back to the initial Vulkan renderer

OS/device including version: Fedora 33, GeForce GTX 1080

Issue description: Unlike Godot 3.x's GLES3 and GLES2 renderers, the Vulkan renderer uses linear filtering when Half Resolution is enabled in the 3D viewport's Perspective menu. However, with a resolution scale of 50%, you can use nearest-neighbor filtering to benefit from a sharper image with no performance cost – in fact, nearest-neighbor filtering can be minutely faster.

We should revert to the 3.x behavior, at least when an integer scaling factor is used (1/2, 1/3, 1/4, …).

I think that by default, the engine should use nearest-neighbor filtering when using an integer scale factor and linear filtering with fractional scale factors (or scale factors above 100%). A Viewport property could be added to toggle between "Automatic", "Always Linear" and "Always Nearest" filtering modes.

See https://tanalin.com/en/articles/integer-scaling/ for more information.

Steps to reproduce: In a 4.0 development build, enable Half Resolution in the 3D viewport's Perspective menu.

Minimal reproduction project: N/A

[KoBeWi]

I added this line:

subviewport_container->set_texture_filter(shrink ? TEXTURE_FILTER_NEAREST : TEXTURE_FILTER_PARENT_NODE);

here:

godot/editor/plugins/node_3d_editor_plugin.cpp

Lines 414 to 417 in ecde7ce

	void Node3DEditorViewport::_update_shrink() {
	bool shrink = view_menu->get_popup()->is_item_checked(view_menu->get_popup()->get_item_index(VIEW_HALF_RESOLUTION));
	subviewport_container->set_stretch_shrink(shrink ? 2 : 1);
	}

Before this change:

After this change:

Does this solve the issue? 🤔

[Calinou]

I added this line:
...
Does this solve the issue? 🤔

Looks like that fixes it 🙂

That said, it may be better to rework Half Resolution to set the Viewport's scaling_3d_scale instead of shrinking the viewport. This is only available in 4.0, not in 3.x. This doesn't support nearest-neighbor filtering yet, but this should be straightforward to add.

[KoBeWi]

That said, it may be better to rework Half Resolution to set the Viewport's scaling_3d_scale instead of shrinking the viewport.

Open a new issue for this.