function edgeEventByPoints implement changes from C++ to better support Collinear points

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Mário Silva

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Nov 20, 2015, 6:16:38 AM11/20/15

to poly2tri

Hi there,

I would like to say i love this lib and i would like to contribute this improvement.

I have integrated the changes in the c++ version on the function edgeEventByPoints. here is the code:

function edgeEventByPoints(tcx, ep, eq, triangle, point) {
    if (isEdgeSideOfTriangle(triangle, ep, eq)) {
        return;
    }


    var p1 = triangle.pointCCW(point);
    var o1 = orient2d(eq, p1, ep);


    if (o1 === Orientation.COLLINEAR) {
        if (triangle.containsPoints(eq, p1)) {
            triangle.markConstrainedEdgeByPoints(eq, p1);
            // We are modifying the constraint maybe it would be better to 
            // not change the given constraint and just keep a variable for the new constraint
            tcx.edge_event.constrained_edge.q = p1;
            var nbTriangle = triangle.neighborAcross(point);
            edgeEventByPoints(tcx, ep, p1, nbTriangle, p1);
        }
        else {
            throw new PointError('poly2tri EdgeEvent: Collinear not supported!', [eq, p1, ep]);
        }
        return;
    }


    var p2 = triangle.pointCW(point);
    var o2 = orient2d(eq, p2, ep);


    if (o2 === Orientation.COLLINEAR) {
        if (triangle.containsPoints(eq, p2)) {
            triangle.markConstrainedEdgeByPoints(eq, p2);
            // We are modifying the constraint maybe it would be better to 
            // not change the given constraint and just keep a variable for the new constraint
            tcx.edge_event.constrained_edge.q = p2;
            var nbTriangle = triangle.neighborAcross(point);
            edgeEventByPoints(tcx, ep, p2, nbTriangle, p2);
        }
        else {
            throw new PointError('poly2tri EdgeEvent: Collinear not supported!', [eq, p2, ep]);
        }
        return;
    }


    if (o1 === o2) {
        // Need to decide if we are rotating CW or CCW to get to a triangle
        // that will cross edge
        if (o1 === Orientation.CW) {
            triangle = triangle.neighborCCW(point);
        } else {
            triangle = triangle.neighborCW(point);
        }
        edgeEventByPoints(tcx, ep, eq, triangle, point);
    } else {
        // This triangle crosses constraint so lets flippin start!
        flipEdgeEvent(tcx, ep, eq, triangle, point);
    }
}