arcFrom2Points vex

arcFrom2Points.vfl

function int[] arcFrom2Points(vector centerPos; float radius; int totalPoints;
                                 vector startPos, endPos;
                                 string direction) {

    float threshold = 0.01;
    if(radius < threshold) {
        return{};
    }

    float TWO_PI = PI * 2;

    vector v1 = normalize(startPos - centerPos);
    vector v2 = normalize(endPos - centerPos);
    float startRad = atan2(v1.z, v1.x);
    // (atan2(v2.z, v2.x) - startRad) - (atan2(v1.z, v1.x) - startRad) ベクトルを{1,0,0}に初期化する
    float rad = startRad*2 - atan2(v2.z, v2.x) - atan2(v1.z, v1.x);
    if((rad < 0) && (direction == "Left")) {
        rad += TWO_PI;
    } else if((rad > 0) && (direction == "Right")) {
        rad -= TWO_PI;
    }

    int points[];
    for(int i = 0; i <= totalPoints; i++) {
        vector pos = set(
            centerPos.x + radius * cos(startRad - i * (rad/totalPoints)),
            centerPos.y,
            centerPos.z + radius * sin(startRad - i * (rad/totalPoints))
        );
        int pointN = addpoint(0, pos);
        setpointattrib(0, "arcLength", pointN, rad*TWO_PI);
        setpointattrib(0, "dictCenter", pointN, normalize(centerPos - pos));

        if(direction == "Right") {
            setpointattrib(0, "N", pointN, normalize(centerPos - pos));
        }
        if(direction == "Left") {
            setpointattrib(0, "N", pointN, normalize(pos - centerPos));
        }

        push(points, pointN);
    }

    // debug 
    // addprim(0, "polyline", addpoint(0, centerPos + v1 * radius), addpoint(0, centerPos));
    // addprim(0, "polyline", addpoint(0, centerPos + v2 * radius), addpoint(0, centerPos));

    return points;
}