Point3d point = curve.GetPointAtParameter(5);
Circle circle = new Circle(point, Vector3d.ZAxis, 0.2);
circle.ColorIndex = 2;
circle.LineWeight = LineWeight.LineWeight015;
circle.AddEntity();

Point3d point = new Point3d(5, 5, 0);
double par = curve.GetParameterAtPoint(point);

double dis = curve.GetDistanceAtParameter(2.5);

double par = curve.GetParameterAtDistance(7);

Point3d point = new Point3d(3,4,0);
double dis = curve.GetDistAtPoint(point);

Point3d point = curve.GetPointAtDist(9.5);

Vector3d vector = curve.GetFirstDerivative(new Point3d(3,0,0));

Vector3d vector = curve.GetFirstDerivative(1.5);

Vector3d vector = curve.GetSecondDerivative(new Point3d(3, 2, 0));

Vector3d vector = curve.GetSecondDerivative(Math.PI);

Point3d point = new Point3d(1.5, 1, 0);
Point3d p = curve.GetClosestPointTo(point, new Vector3d(1, 0, 0), false);

Point3d point = new Point3d(1.5, 1, 0);
Point3d p = curve.GetClosestPointTo(point, false);

Plane plane = new Plane(new Point3d(),new Vector3d(1,0,1));
curve = curve.GetOrthoProjectedCurve(plane);

Plane plane = new Plane(new Point3d(0,0,1),Vector3d.ZAxis);
curve = curve.GetProjectedCurve(plane,new Vector3d(0,0,2));

DBObjectCollection dbs = curve.GetOffsetCurves(1);

DBObjectCollection dbs = curve.GetOffsetCurvesGivenPlaneNormal(new Vector3d(0, 0, -1),1);

Point3dCollection pos = new Point3dCollection();
double dis = curve.GetDistanceAtParameter(curve.EndParam);
pos.Add(curve.GetPointAtDist(dis / 3));
pos.Add(curve.GetPointAtDist(dis / 3 * 2));
DBObjectCollection dbs = curve.GetSplitCurves(pos);

DoubleCollection ds = new DoubleCollection();
double par = curve.EndParam - curve.StartParam;
ds.Add(curve.StartParam + par / 3);
ds.Add(curve.StartParam + par / 3 * 2);
DBObjectCollection dbs = curve.GetSplitCurves(ds);

curve.Extend(false, new Point3d(15, 15, 0));

curve.Extend(2);

curve.ReverseCurve();

Curve3d curve3d=curve.GetGeCurve();

不懂

LineSegment3d line3d = new LineSegment3d(new Point3d(), new Point3d(10, 10, 0));
Line line = Curve.CreateFromGeCurve(line3d) as Line;

不懂

不懂

不懂

LineSegment3d line3d = new LineSegment3d(new Point3d(), new Point3d(10, 10, 0));
Line line = new Line(new Point3d(5, 5, 0), new Point3d(20, 0, 0));
line.SetFromGeCurve(line3d);

不懂

不懂

不懂

Line line = new Line();

Point3d point1 = new Point3d(0, 0, 0);
Point3d point2 = new Point3d(10, 10, 0);
Line line = new Line(point1, point2);

Circle circle = new Circle();

Point3d center = new Point3d(0, 0, 0);
Vector3d normal = Vector3d.ZAxis;
double radius = 5;
Circle circle = new Circle(center, normal, radius);

Arc arc = new Arc();

Point3d center = Point3d.Origin;
double radius = 5;
double startAngle = 0;
double endAngle = Math.PI / 3;
Arc arc = new Arc(center, radius, startAngle, endAngle);

Point3d center = Point3d.Origin;
Vector3d normal = -Vector3d.ZAxis;
double radius = 5;
double startAngle = 0;
double endAngle = Math.PI / 3;
Arc arc = new Arc(center, normal, radius, startAngle, endAngle);

Ellipse ellipse = new Ellipse();

Point3d center = new Point3d(0, 0, 0);
Vector3d unitNormal= Vector3d.ZAxis;
Vector3d majorAxis = new Vector3d(10, 0, 0);
double radiusRatio = 0.5;
double startAngle = 0;
double endAngle = Math.PI * 2;
Ellipse ellipse = new Ellipse(center, unitNormal, majorAxis, radiusRatio, startAngle, endAngle);

Ellipse ellipse = new Ellipse();
Point3d center = new Point3d(0, 0, 0);
Vector3d unitNormal = Vector3d.ZAxis;
Vector3d majorAxis = new Vector3d(10, 0, 0);
double radiusRatio = 0.5;
double startAngle = Math.PI / 3;
double endAngle = Math.PI / 3 * 2;
ellipse.Set(center, unitNormal, majorAxis, radiusRatio, startAngle, endAngle);

double value = ellipse.GetParameterAtAngle(Math.PI / 3);

double angle = ellipse.GetAngleAtParameter(2);

Polyline polyline = new Polyline();

int vertices = 5;
Polyline polyline = new Polyline(vertices);

Polyline polyline = new Polyline();
polyline.ConvertFrom(polyline2D, false);

Polyline2d polyline2D = polyline.ConvertTo(false);

List<Point3d> points = new List<Point3d>();
for (int i = 0; i < polyline.NumberOfVertices; i++)
{
    Point3d point3D = polyline.GetPoint3dAt(i);
    points.Add(point3D);
}

int index = 1;
SegmentType segmentType = polyline.GetSegmentType(index);

int index = 1;
LineSegment2d lineSegment2D = polyline.GetLineSegment2dAt(index);

int index = 1;
CircularArc2d circularArc2D = polyline.GetArcSegment2dAt(index);

int index = 1;
LineSegment3d lineSegment3D=polyline.GetLineSegmentAt(index);

int index = 1;
CircularArc3d circularArc3D=polyline.GetArcSegmentAt(index);

Point3d pt3d = polyline.GetPointAtDist(1200);
Point2d pt2d = new Point2d(pt3d.X, pt3d.Y);
double vaule = 60;
bool b = polyline.OnSegmentAt(index, pt2d, vaule);

Polyline polyline = new Polyline();
polyline.AddVertexAt(0, new Point2d(0, 0), 0, 0, 0);
polyline.AddVertexAt(1, new Point2d(10, 0), 0, 0, 0);
polyline.AddVertexAt(1, new Point2d(5, 5), 0, 2, 1);

polyline.RemoveVertexAt(1);

Point2d point2D = polyline.GetPoint2dAt(1);

Point2d point2D = new Point2d(5, 5);
polyline.SetPointAt(1, point2D);

double bulge = polyline.GetBulgeAt(0); 

polyline.SetBulgeAt(0, 2);

double startWidth=polyline.GetStartWidthAt(0);

double endWidth = polyline.GetEndWidthAt(0);

polyline.SetStartWidthAt(0, 2);

 polyline.SetEndWidthAt(0, 2);

 polyline.MinimizeMemory();

 polyline.MaximizeMemory();

polyline.Reset(true, 1); 

Database database = HostApplicationServices.WorkingDatabase;
string name = "STANDARD";
ObjectId objectId = ObjectId.Null;
using (Transaction trans = database.TransactionManager.StartTransaction())
{
    DBDictionary ss = (DBDictionary)database.MLStyleDictionaryId.GetObject(OpenMode.ForRead);
    foreach (var item in ss)
    {
        if (item.Key.ToUpper() == name)
        {
            objectId = item.Value;
        }
    }
}
Mline mline = new Mline();
mline.Style = objectId;
mline.Normal = Vector3d.ZAxis;

Point3d point3D1 = new Point3d(0, 0, 0);
Point3d point3D2 = new Point3d(10, 10, 0);
mline.AppendSegment(point3D1);
mline.AppendSegment(point3D2);

Point3d lastVertex = new Point3d();
mline.RemoveLastSegment(lastVertex);

Point3d newPosition = new Point3d(10, 20, 0);
mline.MoveVertexAt(1, newPosition);

未知。希望你的补充

Point3d point3D = mline.VertexAt(1);

Point3d pt = new Point3d(0, 5, 0);
Vector3d vector3D = new Vector3d(-1, -1, 0);
var po = mline.GetClosestPointTo(pt, vector3D, false, false);

Point3d pt = new Point3d(0, 5, 0);
var po = mline.GetClosestPointTo(pt, false, false);

Polyline3d polyline3D = new Polyline3d();

Poly3dType poly3DType = Poly3dType.SimplePoly;
Point3dCollection point3DCollection = new Point3dCollection();
point3DCollection.Add(new Point3d(0, 0, 0));
point3DCollection.Add(new Point3d(10, 0, 0));
point3DCollection.Add(new Point3d(10, 10, 0));
bool isClosed = true;
Polyline3d polyline3D = new Polyline3d(poly3DType, point3DCollection, isClosed);

Poly3dType poly3DType = Poly3dType.CubicSplinePoly;
polyline3D.ConvertToPolyType(poly3DType);

polyline3D.Straighten();

polyline3D.SplineFit(Poly3dType.QuadSplinePoly, 3);

polyline3D.SplineFit();

PolylineVertex3d polylineVertex3D = new PolylineVertex3d(new Point3d(10, 10, 0));
Database db = HostApplicationServices.WorkingDatabase;
using (Transaction trans=db.TransactionManager.StartTransaction())
{
    polyline3D = polyline3D.ObjectId.GetObject(OpenMode.ForWrite) as Polyline3d;
    polyline3D.AppendVertex(polylineVertex3D);
    trans.Commit();
}

Database db = HostApplicationServices.WorkingDatabase;
using (Transaction trans= db.TransactionManager.StartTransaction())
{
    polyline3D = polyline3D.ObjectId.GetObject(OpenMode.ForWrite) as Polyline3d;
    int n = 0;
    foreach (ObjectId item in polyline3D)
    {
        if (n == 1)
        {
            PolylineVertex3d polylineVertex3D = new PolylineVertex3d(new Point3d(20, 10, 0));
            polyline3D.InsertVertexAt(item, polylineVertex3D);
            break;
        }
        n++;
    }
    trans.Commit();
}

int n = 0;
foreach (PolylineVertex3d item in polyline3D)
{
    if (n == 1)
    {
        PolylineVertex3d polylineVertex3D = new PolylineVertex3d(new Point3d(20, 10, 0));
        polyline3D.InsertVertexAt(item, polylineVertex3D);
        break;
    }
    n++;
}

foreach (PolylineVertex3d item in polyline3D)
{
                
}

Polyline2d polyline2D = new Polyline2d();

Point3dCollection pos = new Point3dCollection
{
    new Point3d(0, 0, 0),
    new Point3d(10, 0, 0),
    new Point3d(10, 10, 0),
    new Point3d(20, 10, 0)
};
DoubleCollection doubles = new DoubleCollection
{
    0,
    0,
    0,
    0
};
Polyline2d polyline2D = new Polyline2d(Poly2dType.SimplePoly, pos, 0, false, 0, 0, doubles);

polyline2D.ConvertToPolyType(Poly2dType.FitCurvePoly);

polyline2D.Straighten();

polyline2D.SplineFit(Poly2dType.CubicSplinePoly, 100);

polyline2D.SplineFit();

polyline2D.CurveFit();

Vertex2d vertex2D = new Vertex2d(new Point3d(20, 20, 0), 0, 0, 0, 0);
polyline2D.NonDBAppendVertex(vertex2D);

Vertex2d vertex2D = new Vertex2d(new Point3d(20, 20, 0), 0, 0, 0, 0);
Database db = HostApplicationServices.WorkingDatabase;
using (Transaction trans = db.TransactionManager.StartTransaction())
{
    polyline2D.ObjectId.GetObject(OpenMode.ForWrite);
    polyline2D.AppendVertex(vertex2D);
    trans.Commit();
}

Database db = HostApplicationServices.WorkingDatabase;
using (Transaction trans = db.TransactionManager.StartTransaction())
{
    polyline2D.ObjectId.GetObject(OpenMode.ForWrite);
    int n = 0;
    foreach (ObjectId item in polyline2D)
    {
        if (n == 1)
        {
            Vertex2d vertex2D = new Vertex2d(new Point3d(15, 5, 0), 0, 0, 0, 0);
            polyline2D.InsertVertexAt(item, vertex2D);
            break;
        }
        n++;
    }
    trans.Commit();
}

int n = 0;
foreach (Vertex2d item in polyline2D)
{
    if (n == 1)
    {
        Vertex2d vertex2D = new Vertex2d(new Point3d(15, 8, 0), 0, 0, 0, 0);
        polyline2D.InsertVertexAt(item, vertex2D);
        break;
    }
    n++;
}

//IEnumerator enumerator = polyline2D.GetEnumerator();
//var obj = enumerator.Current;
//enumerator.MoveNext();
foreach (var item in polyline2D)
{

}

foreach (Vertex2d item in polyline2D)
{
    Point3d point3D = polyline2D.VertexPosition(item);
}

DBText dBText = new DBText();

Xline xline = new Xline();
xline.BasePoint = new Point3d();
xline.UnitDir = new Vector3d(10, 10, 0);

Ray ray = new Ray();
ray.BasePoint = new Point3d();
ray.UnitDir = new Vector3d(10, 10, 0);

Point3d point = new Point3d();
Vector3d vector = new Vector3d(1, 1, 0);
List<Curve> curves = SelectEntities<Curve>();
if (curves.Count == 0) return;
Curve curve = GetClosestCurve(point, vector, curves);
if (curve == null) return;
Curve curve1 = curve.Clone() as Curve;
curve1.ColorIndex = 2;
curve1.AddEntity();

private static Curve GetClosestCurve(Point3d point, Vector3d vector, List<Curve> curves)
{
    Ray ray = new Ray();
    ray.BasePoint = point;
    ray.UnitDir = vector;
    Point3d closestPoint = new Point3d();
    double closestDis = double.MaxValue;
    Curve closestCur = null;
    foreach (var curve in curves)
    {
        Point3dCollection pos = new Point3dCollection();
        ray.IntersectWith(curve, Intersect.OnBothOperands, pos, IntPtr.Zero, IntPtr.Zero);
        foreach (Point3d po in pos)
        {
            double dis = po.DistanceTo(point);
            if (dis < closestDis)
            {
                closestPoint = po;
                closestDis = dis;
                closestCur = curve;
            }
        }
    }
    return closestCur;
}

RotatedDimension rotatedDimension = new RotatedDimension();

double rotation = Math.PI / 6;
Point3d line1Point = new Point3d(0, 0, 0);
Point3d line2Point = new Point3d(100, 0, 0);
Point3d dimensionLinePoint = new Point3d(50, 30, 0);
string dimensionText = "150";
Document doc = Application.DocumentManager.MdiActiveDocument;
ObjectId dimensionStyle = doc.Database.DimStyleTableId;
RotatedDimension rotatedDimension = new RotatedDimension(rotation, line1Point, line2Point, dimensionLinePoint,dimensionText, dimensionStyle);

AlignedDimension alignedDimension = new AlignedDimension();

Point3d line1Point = new Point3d(0, 0, 0);
Point3d line2Point = new Point3d(100, 0, 0);
Point3d dimensionLinePoint = new Point3d(50, 30, 0);
string dimensionText = "";
Document doc = Application.DocumentManager.MdiActiveDocument;
ObjectId dimensionStyle = doc.Database.DimStyleTableId;
AlignedDimension alignedDimension = new AlignedDimension(line1Point, line2Point, dimensionLinePoint, dimensionText,
dimensionStyle);

LineAngularDimension2 lineAngularDimension2 = new LineAngularDimension2();

Point3d line1Start = new Point3d(0, 0, 0);
Point3d line1End = new Point3d(0, 50, 0);
Point3d line2Start = new Point3d(10, 0, 0);
Point3d line2End = new Point3d(50, 50, 0);
Point3d arcPoint = new Point3d(30, 80, 0);
string dimensionText = "";
Document doc = Application.DocumentManager.MdiActiveDocument;
ObjectId dimensionStyle = doc.Database.DimStyleTableId;
LineAngularDimension2 lineAngularDimension2 = new LineAngularDimension2(line1Start,line1End,line2Start,line2End, arcPoint,
dimensionText, dimensionStyle);

RadialDimension radialDimension = new RadialDimension();

Point3d center = new Point3d(0, 0, 0);
Point3d chordPoint = new Point3d(50, 50, 0);
double leaderLength = 100;
string dimensionText = "";
Document doc = Application.DocumentManager.MdiActiveDocument;
ObjectId dimensionStyle = doc.Database.DimStyleTableId;
RadialDimension radialDimension = new RadialDimension(center, chordPoint, leaderLength, dimensionText,
dimensionStyle);
AddEntity(radialDimension);

DiametricDimension diametricDimension = new DiametricDimension();

Point3d chordPoint = new Point3d(50, 0, 0);
Point3d farChordPoint = new Point3d(-50, 0, 0);
double leaderLength = 20;
string dimensionText = "";
Document doc = Application.DocumentManager.MdiActiveDocument;
ObjectId dimensionStyle = doc.Database.DimStyleTableId;
DiametricDimension diametricDimension = new DiametricDimension(chordPoint, farChordPoint,leaderLength,
dimensionText,dimensionStyle);
AddEntity(diametricDimension);

Point3d centerPoint = new Point3d(0, 0, 0);
Point3d xLine1Point = new Point3d(0, 50, 0);
Point3d xLine2Point = new Point3d(50, 0, 0);
Point3d arcPoint = new Point3d(70, 70, 0);
string dimensionText = "";
Document doc = Application.DocumentManager.MdiActiveDocument;
ObjectId dimensionStyle = doc.Database.DimStyleTableId;
ArcDimension arcDimension = new ArcDimension(centerPoint, xLine1Point, xLine2Point, arcPoint, dimensionText,
dimensionStyle);
AddEntity(arcDimension);

OrdinateDimension ordinateDimension = new OrdinateDimension();

bool useXAxis = true;
Point3d definingPoint = new Point3d(50, 20, 0);
Point3d leaderEndPoint = new Point3d(70, 50, 0);
string dimensionText = "";
Document doc = Application.DocumentManager.MdiActiveDocument;
ObjectId dimensionStyle = doc.Database.DimStyleTableId;
OrdinateDimension ordinateDimension = new OrdinateDimension(useXAxis, definingPoint, leaderEndPoint,
dimensionText,dimensionStyle);

LineSegment3d line = new LineSegment3d();

Point3d point1 = new Point3d(0, 0, 0);
Point3d point2 = new Point3d(10, 0, 0);
LineSegment3d line = new LineSegment3d(point1, point2);

Point3d point = new Point3d(0, 0, 0);
Vector3d vector = new Vector3d(10, 0, 0);
LineSegment3d line = new LineSegment3d(point, vector);

Point3d point = new Point3d(0, 0, 0);
Vector3d vector = new Vector3d(0, 0, 10);
LineSegment3d line = new LineSegment3d(point, vector);
Plane plane = line.GetBisector();

Point3d point = new Point3d(0, 0, 0);
Vector3d vector = new Vector3d(10, 0, 0);
LineSegment3d line = new LineSegment3d(point, vector);
Point3d point1 = line.BaryComb(0.6);//(6,0,0)
Point3d point2 = line.BaryComb(-2);//(-20,0,0)
Point3d point3 = line.BaryComb(3);//(30,0,0)

Point3d point = new Point3d(0, 0, 0);
Vector3d vector = new Vector3d(10, 0, 0);
LineSegment3d line = new LineSegment3d(point, vector);
Point3d point1 = new Point3d(5, 5, 0);
Point3d point2 = new Point3d(10, 10, 0);
line.Set(point1, point2);

Point3d point = new Point3d(0, 0, 0);
Vector3d vector = new Vector3d(10, 0, 0);
LineSegment3d line = new LineSegment3d(point, vector);
Point3d point1 = new Point3d(5, 5, 0);
Vector3d vector1 = new Vector3d(5, 5, 0);
line.Set(point1, vector1);

Circle circle = new Circle(new Point3d(), Vector3d.ZAxis, 10);
Curve3d curve = circle.GetGeCurve();
Point3d point = new Point3d(20, 0, 0);
double parameter = 1;
LineSegment3d line = new LineSegment3d();
line.Set(curve, point, parameter);

//扩展一下。求点到圆的两个切线
Circle circle = new Circle(new Point3d(), Vector3d.ZAxis, 10);
Curve3d curve = circle.GetGeCurve();
Point3d point = new Point3d(20, 0, 0);
List<LineSegment3d> lines = new List<LineSegment3d>();
for (double i = 0; i < Math.PI * 2; i += 0.1)
{
    LineSegment3d line = new LineSegment3d();
    line.Set(curve, point, i);
    if (lines.Any(l => l.EndPoint == line.EndPoint)) continue;
    lines.Add(line);
}

Circle circle1 = new Circle(new Point3d(), Vector3d.ZAxis, 10);
Circle circle2 = new Circle(new Point3d(50,0,0), Vector3d.ZAxis, 20);
Curve3d curve1 = circle1.GetGeCurve();
Curve3d curve2 = circle2.GetGeCurve();
double parameter1 = 1.5;
double parameter2 = 1.5;
LineSegment3d line = new LineSegment3d();
line.Set(curve1, curve2, parameter1, parameter2);

//扩展一下。求两个圆的四个切线
Circle circle1 = new Circle(new Point3d(), Vector3d.ZAxis, 10);
Circle circle2 = new Circle(new Point3d(50, 0, 0), Vector3d.ZAxis, 20);
Curve3d curve1 = circle1.GetGeCurve();
Curve3d curve2 = circle2.GetGeCurve();
List<LineSegment3d> lines = new List<LineSegment3d>();
for (double i = 0; i < Math.PI*2; i += 0.1)
{
    for (double j = 0; j < Math.PI * 2; j += 0.1)
    {
        LineSegment3d line = new LineSegment3d();
        line.Set(curve1, curve2, i, j);
        if (lines.Any(l => l.StartPoint == line.StartPoint || l.EndPoint == line.EndPoint)) continue;
        lines.Add(line);
    }
}
lines.ForEach(l => Curve.CreateFromGeCurve(l).AddEntity());
circle1.AddEntity();
circle2.AddEntity();