Clipping planes invert distance sign

[ggetz]

Adjust Plane.transform function and adjusted distance sign accordingly.

[cesium-concierge]

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[pjcozzi]

@lilleyse just a reminder that this is a not a breaking change; transform was added this release.

[hpinkos]

@ggetz this all looks fine to me. Are we sure we have it right this time? Is there an equation we followed to write the Plane.transform function? I just don't want to merge this without understanding why we had to make this change.

[ggetz]

I was using the definition of plane.distance opposite of what was previously defined:

The shortest distance from the origin to the plane. The sign of distance determines which side of the plane the origin is on. If distance is positive, the origin is in the half-space in the direction of the normal; if negative, the origin is in the half-space opposite to the normal; if zero, the plane passes through the origin.

So when computing the position representing the location of the plane, we need to multiply the normal by the opposite of the distance, rather than the distance as is.

[hpinkos]

Great, sounds good @ggetz!

I think this is good to go, but I'll leave it open until the 2nd so @lilleyse can take a quick look at it and merge before the release

[lilleyse]

So when computing the position representing the location of the plane, we need to multiply the normal by the opposite of the distance, rather than the distance as is.

Alright, that does make sense.

I tested out the demos and ran the tests. This change looks good to me.