[css-color-4] Correction to ray trace to avoid throwing off our intersect calculation and match MINDE flow #10579

[facelessuser]

My suggested fix via #10579 (comment) was not the ideal fix and artificially limited tnear. This is a numerical instability issue and should be addressed as such by using an epsilon comparison to prevent rays that are too small. This corrects the fix.

I've also adjusted the algorithm to match the flow of MINDE in regardless to checking lightness before returning out of gamut colors.

I also revised the cleanup step. Since the destination is a gamut-bound space, we can clip there as we do in MINDE.

Related #10579

[svgeesus]

@facelessuser could you please:

1. Create a W3C account, if you don't already have one
2. Link your GitHub and W3C accounts (the menu item "Connected accounts" on your W3C account page).

I can then make a link for an individual royalty free license commitment (for the whole Ray Trace GM, not just this specific pull request). Thanks!

[facelessuser]

Excellent, I'll create an account!

[facelessuser]

Cool, I've made the request and also updated the algorithm to better match the CSS MINDE flow. This also addresses the concern about clipping and converting to the destination space. I've updated it to follow what CSS MINDE does.

A final note, I settled on 1E-12 for the ray size threshold. It's generally recommended either 1E-9 or 1E-12 for high precision cases in double floating point. I'm probably indifferent to whichever, as I don't think there would be a significant difference.

[facelessuser]

I've made the account and linked GitHub.

[svgeesus]

Thanks! The request for non-participant license commitment has been sent.

[facelessuser]

@svgeesus Sorry for not getting back about this, but I currently get the following when I click the link to the non-participant license commitment.

The level of access required for this page is inconsistent with [your account](https://www.w3.org/users/myprofile).
There is not yet an access level assigned to this page. W3C staff may be able to change the access level for this resource using the ,access tool.

[deniak]

@facelessuser you should be able to submit your commitment using this link.

[facelessuser]

For a bit, I was restricted from commenting for some reason, but I've filled out the non-participant license agreement.

[svgeesus]

There is a known problem with the IPR bot currently; I have reported it but meanwhile it is holding up merging any PR with an individual participant commitment (including this one).

[facelessuser]

That makes sense. Thanks for the update. Hopefully we'll get it in sooner rather than later.