Implement boolean algorithm NURBS based BREP about jsketcher HOT 5 CLOSED

see verbnurbs by @pboyer

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Also current algorithm isn't very robust and fails in some corner cases.

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After think twice about the whole things.I think it's a timing to start a new project which include brep, csg algorithms and triangulation algorithms. And take advantage of algorithms supported by verb-nurbs which include tessellate and intersection algorithm of nurbs surface.

I have to learn more about nurbs-surface/curve before doing this.

By the way, triangulation of plane face with nurbs-curve in outer loop can easily improved by add the code below in '.../3d/triangulation.js'

export function TriangulateFace(face) {
function arr(v) {
return [v.x, v.y, v.z];
}

function vertexCallback(data, out) {
out.push(data);
}
function combinecallback(coords, data, weight) {
//throw 'should never happen cuz brep is non-manifold'
}
function edgeCallback(flag) {
}

var tessy = new libtess.GluTesselator();
// tessy.gluTessProperty(libtess.gluEnum.GLU_TESS_WINDING_RULE, libtess.windingRule.GLU_TESS_WINDING_POSITIVE);
tessy.gluTessCallback(libtess.gluEnum.GLU_TESS_VERTEX_DATA, vertexCallback);
tessy.gluTessCallback(libtess.gluEnum.GLU_TESS_BEGIN, begincallback);
tessy.gluTessCallback(libtess.gluEnum.GLU_TESS_ERROR, errorcallback);
tessy.gluTessCallback(libtess.gluEnum.GLU_TESS_COMBINE, combinecallback);
tessy.gluTessCallback(libtess.gluEnum.GLU_TESS_EDGE_FLAG, edgeCallback);

const normal = arr(face.surface.normal);
tessy.gluTessNormal(normal[0], normal[1], normal[2]);

const vertices = [];
tessy.gluTessBeginPolygon(vertices);

for (let loop of face.loops) {
tessy.gluTessBeginContour();
for (let e of loop.halfEdges) {

+++ if(e.edge.curve.isLine)
tessy.gluTessVertex(arr(e.vertexA.point), e.vertexA);
+++ else if(e.edge.curve.isNurbsCurve){
+++ tessy.gluTessVertex(arr(e.vertexA.point), e.vertexA);
+++ let nurbsVectors = e.edge.curve.verb.tessellate()
+++ nurbsVectors.shift()

+++ nurbsVectors.forEach(v => {
+++ let midVertex = new Vertex(v[0], v[1], v[2])
+++ tessy.gluTessVertex(v, midVertex)}
+++ )

  }
}
tessy.gluTessEndContour();

}
....

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@xibyte Thanks for your explain on gluTessNormal. The code before is just for a plane face with nurbs-curve in its ourerLoop. I know it do not works for nurbs -surface. In fact, I found tessellate algorithm was originally supported in verbnurbs by @pboyer .So I think if we can adjust the structure of our code and make use of the algorithm in verbnurb directly ? May be we can even adjust the code in the verbnurbs?

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done in 8204748

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