Line2NodeMaterial: Align wide lines with WebGLRenderer version.

[Mugen87]

Fixed #32229.

Description

As suggested in #32229 (comment), the PR makes sure the wide line implementation for WebGPURenderer uses CSS pixel units to ensure consistent line widths across devices. For this, the DPR must be factored out of the viewport.

With this PR, the wide line demos now render with equal width for WebGPURenderer and WebGLRenderer.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	356.24 86.48	356.24 86.48	+0 B +0 B
WebGPU	610.49 171.27	610.5 171.28	+8 B +7 B
WebGPU Nodes	609.1 171.01	609.1 171.02	+8 B +8 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	488.02 121.25	488.02 121.25	+0 B +0 B
WebGPU	679.43 186.52	679.43 186.52	+0 B +0 B
WebGPU Nodes	621.15 169.7	621.15 169.7	+0 B +0 B

[WestLangley]

In the library, viewport is sometimes defined in physical pixels, and other times in logical pixels. It would be a lot better if there was consistency in this regard -- or improved nomenclature. Perhaps @sunag and @Mugen87 could come to an agreement on this.

[Mugen87]

I agree with what @sunag has defined in #29347.

[WestLangley]

This bug occurred because the definitions are not consistent.

renderer.setViewport() is in logical pixel units. Can you improve the nomenclature?

[Mugen87]

I think there is a difference with what is defined via the renderer API and what TSL objects represent in the shader. That has been mentioned here #29347 (comment). I don't think you can come up with a solution that satisfies every use case. Keeping the TSL objects in physical pixel units seems correct to me. And I would leave the renderer API as it is, especially to avoid any kind of breakage.

[WestLangley]

Keeping the TSL objects in physical pixel units seems correct to me.

Yes.

And I would leave the renderer API as it is,

Yes.

So the only possible changes are in the margins: revist the docs and inline docs and ensure the units are clearly stated.

Also the internal nomenclature could be reviewed.

_viewport // logical (css) pixel units

_currentViewport // physical pixel units

state.viewport // physical pixel units