Change CurveModifier splineTexture filtering to Linear for smoother path

[manthrax]

Related issue: #28376

A clear and concise description of what the problem was and how this pull request solves it.

In the CurveModifier examples there is a lot of jitter and distortionwhen meshes go around the sharper curves:

In the:
https://threejs.org/examples/?q=curve#webgl_modifier_curve_instanced
and:
https://136.24.178.125/three.js/examples/webgl_modifier_curve.html

examples, you can see shimmering as the text instances are curved along their paths around corners.

This is because the splineTexture magFilter is explicitly set to NearestFilter instead of LinearFilter , causing snapping in the splineTexture sampling.

This PR changes the default splineTexture .magFiltering to LinearFiltering to fix this issue.

Here is a glitch that allows changing the magFilter between Linear and Nearest to show the issue:

https://atlantic-warp-sweater.glitch.me/

This contribution is funded by Example

[Mugen87]

Indeed, much smoother!

[Mugen87]

I think NearestFilter was originally used to support more platforms because linear filtering floating point textures is not supported on all hardware. However, the previous quality wasn't good and it seems LinearFiltering is a better default.

If users have to support incompatible hardware, they can still set the filtering via the flow reference back to NearestFilter.

flow.splineTexure.magFilter = THREE.NearestFilter;

[Mugen87]

One possible improvement would be to use a half float texture in CurveModifier. That would require the usage of Uint16Array and DataUtils.toHalfFloat() when updating values into the spline texture. I guess the precision of half float should be enough for this use case.

Linear filtering half float textures always works in WebGL 2.

[Mugen87]

BTW: Why is only magFilter set to LinearFilter? Shouldn't we do the same for minFilter (which is still NearestFilter).

[manthrax]

BTW: Why is only magFilter set to LinearFilter? Shouldn't we do the same for minFilter (which is still NearestFilter).

I saw that but I wasn't clear on the semantics of using LinearFilter for minFilter..

But I think its valid.. so lgtm?