Example usage for com.google.common.geometry S2Cap axis

Introduction

In this page you can find the example usage for com.google.common.geometry S2Cap axis.

Prototype

S2Point axis

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Usage

From source file:org.geosde.cassandra.GeometryTestCase.java

S2Point samplePoint(S2Cap cap) {
    // We consider the cap axis to be the "z" axis. We choose two other axes
    // to//from w w w .j  av a 2 s. c o  m
    // complete the coordinate frame.

    S2Point z = cap.axis();
    S2Point x = z.ortho();
    S2Point y = S2Point.crossProd(z, x);

    // The surface area of a spherical cap is directly proportional to its
    // height. First we choose a random height, and then we choose a random
    // point along the circle at that height.

    double h = rand.nextDouble() * cap.height();
    double theta = 2 * S2.M_PI * rand.nextDouble();
    double r = Math.sqrt(h * (2 - h)); // Radius of circle.

    // (cos(theta)*r*x + sin(theta)*r*y + (1-h)*z).Normalize()
    return S2Point.normalize(
            S2Point.add(S2Point.add(S2Point.mul(x, Math.cos(theta) * r), S2Point.mul(y, Math.sin(theta) * r)),
                    S2Point.mul(z, (1 - h))));
}

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