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https://issues.apache.org/jira/browse/LUCENE-7970?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16178583#comment-16178583
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Ignacio Vera commented on LUCENE-7970:
--------------------------------------
Hi [~daddywri],
Thanks for the patch and the updates. Therefore you need always to be able to
define the shape with a collections of planes. This approach is very nice, it
is like approximating the circle as a polygon with n-sides. I have a look into
the patch and first think I notice is that cardinality points are wrong: 0
degrees bearing angle is for north. I did the following changes and I was able
to build circles:
{{
final GeoPoint eastPoint = planetModel.surfacePointOnBearing(center,
cutoffAngle, Math.PI * 0.5);
final GeoPoint westPoint = planetModel.surfacePointOnBearing(center,
cutoffAngle, Math.PI * 1.5);
final GeoPoint northPoint = planetModel.surfacePointOnBearing(center,
cutoffAngle, 0.0);
final GeoPoint southPoint = planetModel.surfacePointOnBearing(center,
cutoffAngle, Math.PI);
this.edgePoints = new GeoPoint[]{northPoint};
if (planetModel.c > planetModel.ab) {
// z can be greater than x or y, so ellipse is longer in height than
width
slices.add(new ApproximationSlice(center, eastPoint, Math.PI * 0.5,
westPoint, Math.PI * -0.5, northPoint, 0));
slices.add(new ApproximationSlice(center, westPoint, 1.5 * Math.PI,
eastPoint, 0.5 * Math.PI, southPoint, Math.PI));
} else {
// z will be less than x or y, so ellipse is shorter than it is tall
slices.add(new ApproximationSlice(center, northPoint, 2 * Math.PI ,
southPoint, Math.PI, eastPoint, 1.5 * Math.PI));
slices.add(new ApproximationSlice(center, southPoint, Math.PI,
northPoint, Math.PI * 0.0, westPoint, 0.5 * Math.PI));
}}
Note I have to change the bearing angles of the slice so averages give the
expected numbers. I need to look a bit further but it is looking very nice.
Thanks!
I.
> Add a Geo3d shape that models an exact circle, even when the planet model is
> not a sphere
> -----------------------------------------------------------------------------------------
>
> Key: LUCENE-7970
> URL: https://issues.apache.org/jira/browse/LUCENE-7970
> Project: Lucene - Core
> Issue Type: Improvement
> Components: modules/spatial3d
> Reporter: Ignacio Vera
> Assignee: Karl Wright
> Attachments: circle.jpg, LUCENE-7970-exact.diff, LUCENE_7970.patch,
> LUCENE-7970.patch, LUCENE-7970-proposed.patch,
> LUCENE-7970_testBearingPoint.patch
>
>
> Hi [~Karl wright],
> How circles are currently build do not behave very well when the planet model
> is not an sphere. when you are close to the border in WGS84 you might get
> false positves or false negatives when checking if a point is WITHIN. I think
> the reason is how the points to generate the circle plane are generated which
> assumes a sphere.
> My proposal is the following:
> Add a new method to PlanetModel:
> public GeoPoint pointOnBearing(GeoPoint from, double dist, double bearing);
> Which uses and algorithm that takes into account that the planet might not be
> spherical. For example Vincenty's formulae
> (https://en.wikipedia.org/wiki/Vincenty%27s_formulae).
> Use this method to generate the points for the circle plane. My experiments
> shows that this approach removes false negatives in WGS84 meanwhile it works
> nicely in the Sphere.
> Does it make sense?
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