Error in Angle2d and Angle3d angle() calculation about jzy3d-api HOT 2 CLOSED

PS - I wrote the following brute force code, based on formulas from Wikipedia, to test against Angle2d and Angle3d. This code appears to give the correct answer, but it seems always to return an angle of 180 deg or less whereas Angle2d and Angle3d will return values of 360 deg or less. This code does seem to run about 50% faster than the current Angle2d and Angle3d code:

/**
* Calculate the angle at the vertex between two vectors formed by three 2d points.
*
* @param a A 2d point.
* @param vertex The vertex point.
* @param b A 2d point.
*
* @return The angle, from 0 to 2 * PI, in radians.
*/
public static double calculateAngle(Coord2d a, Coord2d vertex, Coord2d b) {
double lengthAB = Math.sqrt(Math.pow(a.x - b.x, 2) + Math.pow(a.y - b.y, 2));
double lengthAV = Math.sqrt(Math.pow(a.x - vertex.x, 2) + Math.pow(a.y - vertex.y, 2));
double lengthBV = Math.sqrt(Math.pow(b.x - vertex.x, 2) + Math.pow(b.y - vertex.y, 2));
double numerator = Math.pow(lengthAV, 2) + Math.pow(lengthBV, 2) - Math.pow(lengthAB, 2);
double denominator = 2 * lengthAV * lengthBV;
return Math.acos(numerator / denominator);
}

/**
 * Calculate the angle at the vertex between two rays formed by three 3d points.
 * 
 * @param a A 3d point.
 * @param vertex The vertex point.
 * @param b A 3d point.
 * 
 * @return The angle, from 0 to 2 * PI, in radians.
 */
public static double calculateAngle(Coord3d a, Coord3d vertex, Coord3d b) {
    double lengthAB = Math.sqrt(Math.pow(a.x - b.x, 2) + Math.pow(a.y - b.y, 2) + Math.pow(a.z - b.z, 2));
    double lengthAV = Math.sqrt(Math.pow(a.x - vertex.x, 2) + Math.pow(a.y - vertex.y, 2) + Math.pow(a.z - vertex.z, 2));
    double lengthBV = Math.sqrt(Math.pow(b.x - vertex.x, 2) + Math.pow(b.y - vertex.y, 2) + Math.pow(b.z - vertex.z, 2));
    double numerator = Math.pow(lengthAV, 2) + Math.pow(lengthBV, 2) - Math.pow(lengthAB, 2);
    double denominator = 2 * lengthAV * lengthBV;
    return Math.acos(numerator / denominator);
}

Thanks,
Lloyd

from jzy3d-api.

Thank you Lloyd.
Looks like method angle() in Angle2d and Angle3d is not called by any class of the framework, so you might change the contract without breaking the framework.
Almost ready for a pull request? :)

from jzy3d-api.