Problems with raycasting on LineSegments after r163

[jonathanzopes]

Description

Hi,

After upgrading from r163 to r171, I see some issues with raycasting on LineSegments. In particular, the resulting index on the intersections seems to be off for me.

For me it's not easy to generate a reproducible example right now: In any case, I wonder if it's related to #28114, where the index changed from i to a. Here is the related line.

Thanks, for any feedback.

Reproduction steps

1. Perform raycasting on LineSegments
2. Inspect index on intersection with version r163 vs r164+

Version

r163

Browser

Chrome/Edge

OS

Windows

[Mugen87]

For me it's not easy to generate a reproducible example right now:

Is the issue not deterministic? Without an live example it will be difficult to pinpoint the issue.

BTW: The official line raycasting demo seems to work without issues: https://threejs.org/examples/webgl_interactive_lines

[jonathanzopes]

Thanks for the quick reply!

No it's deterministic.

I can try to adjust the example you shared (just don't have the time right now), the example seems to use the point property to set the position of the "intersection-sphere", but in my use-case I use the index property.

[Mugen87]

/cc @zoeeer

[gkjohnson]

Looks like #28114 changed the resulting index to the vertex index stored in the index buffer rather than the line segment index from the loop as it was previously.

[Mugen87]

I vote to revert to the original index. I think this has been changed by accident, at least I wasn't aware of a change in that regard.

[jonathanzopes]

Ok, thanks. I attempted to provide a PR.

[gkjohnson]

I vote to revert to the original index. I think this has been changed by accident, at least I wasn't aware of a change in that regard.

Agreed. The vertex index is useless as it is since you can't know what the subsequent end point is.