Hi Brian,

Here's a function for checking if a pair of curves is G1.

- Peer

// returns true if curve1 is tangent to curve2
function getCurvePairIsG1(curve1, curve2) {

    var curve1startPt = curve1.getStartPt();
    var curve1endPt = curve1.getEndPt();
    var curve1startTan = curve1.evaluateTangent(curve1.domainMin);
    var curve1endTan = curve1.evaluateTangent(curve1.domainMax);

    var curve2startPt = curve2.getStartPt();
    var curve2endPt = curve2.getEndPt();
    var curve2startTan = curve2.evaluateTangent(curve2.domainMin);
    var curve2endTan = curve2.evaluateTangent(curve2.domainMax);

    // flip one of the tangent vectors in the pair being compared for end-end and start-start cases
    var curve1startTanNeg = moi.vectorMath.createPoint(curve1startTan.x, curve1startTan.y, curve1startTan.z);
    curve1startTanNeg.scale(-1.0);

    var curve1endTanNeg = moi.vectorMath.createPoint(curve1endTan.x, curve1endTan.y, curve1endTan.z);
    curve1endTanNeg.scale(-1.0);

    var tol = moi.geometryDatabase.tolerance;

    // curve1 start curve2 end
    if (
        moi.vectorMath.distance(curve1startPt, curve2endPt) < tol &&
        moi.vectorMath.distance(curve1startTan, curve2endTan) < tol
    ) {
        return true;
    }

    // curve1 end curve2 start
    else if (
        moi.vectorMath.distance(curve1endPt, curve2startPt) < tol &&
        moi.vectorMath.distance(curve1endTan, curve2startTan) < tol
    ) {
        return true;
    }

    // curve1 start curve2 start
    else if (
        moi.vectorMath.distance(curve1startPt, curve2startPt) < tol &&
        moi.vectorMath.distance(curve1startTanNeg, curve2startTan) < tol
    ) {
        return true;
    }

    // curve2 end curve2 end
    else if (
        moi.vectorMath.distance(curve1endPt, curve2endPt) < tol &&
        moi.vectorMath.distance(curve1endTanNeg, curve2endTan) < tol
    ) {
        return true;
    }

    else {
        return false;
    }
}