Raycaster: Add barycoord to intersection result, make attribution interpolation more convenient.

[gkjohnson]

Related issue: --

Description

Currently raycasting only returns a few pre-interpolated results but not all, which can be useful in cases where other attributes need to be interpolated abitrarily, such as when sampling the recently-added Cesium metadata plugins for 3D Tiles Renderer. This PR outputs the barcoord of the hit point relative to the surface to mesh raycast intersections and adds a getAttributeInterpolationFromBarycoord function to Triangle to make interpolating attributes more convenient.

Currently this is the code that needs to be run to interpolate a uv3 attribute after raycast:

const triangle = new Triangle();
const vec20 = new Vector2();
const vec21 = new Vector2();
const vec22 = new Vector2();
const barycoord = new Vector3();

// ...

const { object, face, point } = hit;

// get barycoord value
triangle.setFromAttributeAndIndices( object.geometry.attributes.position, face.a, face.b, face.c );
triangle.a.applyMatrix4( object.matrixWorld );
triangle.b.applyMatrix4( object.matrixWorld );
triangle.c.applyMatrix4( object.matrixWorld );
triangle.getBarycoord( point, barycoord );

// get attribute values per vertex
const uv3 = object.geometry.attributes.uv3;
vec20.fromBufferAttribute( uv3, face.a );
vec21.fromBufferAttribute( uv3, face.b );
vec22.fromBufferAttribute( uv3, face.c );

// calculate the interpolated value
const result = new Vector2();
result
  .addScaledVector( vec20, barycoord.x )
  .addScaledVector( vec21, barycoord.y )
  .addScaledVector( vec22, barycoord.z );

And this is what it is after:

const { object, face, barycoord } = hit;
const uv3 = object.geometry.attributes.uv3;
const result = new Vector2();
Triangle.getAttributeInterpolationFromBarycoord( uv3, face.a, face.b, face.c, barycoord, result );

This contribution is funded by Cesium GIS Ecosystem Grant

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	685.94 169.78	686.03 169.81	+93 B +30 B
WebGPU	834.9 223.91	835 223.93	+93 B +25 B
WebGPU Nodes	834.41 223.78	834.5 223.81	+93 B +25 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	462.29 111.52	462.34 111.55	+48 B +35 B
WebGPU	531.72 143.33	531.77 143.36	+48 B +26 B
WebGPU Nodes	488.38 133.2	488.43 133.22	+48 B +20 B

[Mugen87]

The change is okay for me 👍 .

Would you still add a documentation for getAttributeInterpolationFromBarycoord()?

[gkjohnson]

Done!

[WestLangley]

How about simply getInterpolatedAttribute().

It is more than just barycoord that you are passing in.

[gkjohnson]

Just renamed it! I think the simpler name is better, as well.