ArrayList<Vector> ps = new ArrayList<Vector>(ids.size());
for(DBID clpnum : ids) {
double[] projP = proj.fastProjectDataToRenderSpace(rel.get(clpnum));
ps.add(new Vector(projP));
}
List<Polygon> polys = (new AlphaShape(ps, alpha * Projection.SCALE)).compute();
for(Polygon p : polys) {
SVGPath path = new SVGPath(p);
Element hulls = path.makeElement(svgp);
addCSSClasses(svgp, cnum, 0.5);
SVGUtil.addCSSClass(hulls, CLUSTERHULL + cnum);