2021-07-05c /cad secondary development create arc (4)

The code is as follows ：
ArcExam.cs

using System;
using System.Collections.Generic;
using System.Text;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;

namespace _2 Graphic Creation 
{
    
    public class ArcExam
    {
    
        [CommandMethod("ArcDemo")]
        public void ArcDemo()
        {
    
            Arc arc1 = new Arc();
            arc1.Center = new Point3d(0, 0, 0);
            arc1.StartAngle = 0;
            arc1.EndAngle = Math.PI;
            arc1.Radius = 100;
            double startDegree = 45;
            Arc arc2 = new Arc(new Point3d(500, 500, 0), 20,BaseTool.DegreeToAngle(startDegree), Math.PI);
            Arc arc3 = new Arc(new Point3d(100, 100, 0), new Vector3d(0, 0, 1), 20, Math.PI / 4, Math.PI / 2);

            Database db = HostApplicationServices.WorkingDatabase;
            AddEnityTool.AddEnityToModelSpace(db, arc1,arc2,arc3);
        }
    }
}

Code parsing ：
The above code is basically for introduction CAD The usage of the inner arc method

Arc arc1 = new Arc();
arc1.Center = new Point3d(0, 0, 0);
arc1.StartAngle = 0;
arc1.EndAngle = Math.PI;
arc1.Radius = 100;

Center The coordinates of the center of the circle ;StartAngle Start the arc ;EndAngle End arc ;Radius radius ;
Note that the attribute here is radian

double startDegree = 45;
Arc arc2 = new Arc(new Point3d(500, 500, 0), 20,BaseTool.DegreeToAngle(startDegree), Math.PI);

Here is also the radian value , We use the angle to radian method created previously to 45 Degrees to radians
From left to right , Followed by the center of the circle 、 radius 、 Start the arc 、 End arc .
arc3 involve Vector3d, I draw a two-dimensional picture , In less than , It refers to Cartesian coordinates .

Draw an arc at three points
The code is as follows ：

using System;
using System.Collections.Generic;
using System.Text;
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;

namespace _2 Graphic Creation 
{
    
    public class ArcExam
    {
    
        [CommandMethod("ArcDemo")]
        public void ArcDemo()
        {
    
            Database db = HostApplicationServices.WorkingDatabase;
            Point3d startPoint = new Point3d(100, 100, 0);
            Point3d endPoint = new Point3d(200, 200, 0);
            Point3d pointOnArc = new Point3d(150, 100, 0);
            CircularArc3d cArc = new CircularArc3d(startPoint,pointOnArc,endPoint);

            double radius = cArc.Radius;
            Point3d center = cArc.Center;
            Vector3d cs = center.GetVectorTo(startPoint);
            Vector3d ce = center.GetVectorTo(endPoint);
            Vector3d xvector = new Vector3d(1, 0, 0);
            double startAngle = cs.Y > 0 ? xvector.GetAngleTo(cs) : -xvector.GetAngleTo(cs);
            double endAngle = ce.Y > 0 ? xvector.GetAngleTo(ce) : -xvector.GetAngleTo(ce);
            Arc arc = new Arc(center,radius,startAngle,endAngle);
            AddEnityTool.AddEnityToModelSpace(db, arc);
        }
    }
}

Code interpretation ：

Database db = HostApplicationServices.WorkingDatabase;
Point3d startPoint = new Point3d(100, 100, 0);
Point3d endPoint = new Point3d(200, 200, 0);
Point3d pointOnArc = new Point3d(150, 100, 0);
CircularArc3d cArc = new CircularArc3d(startPoint,pointOnArc,endPoint);

Three points are created , And then through CircularArc3d Method creates an arc object

Try to use ARC Method to realize three-point circle

double radius = cArc.Radius;
Point3d center = cArc.Center;

First, obtain the radius and center point of the upper arc .

Vector3d cs = center.GetVectorTo(startPoint);
Vector3d ce = center.GetVectorTo(endPoint);

The code here can be passed GetVectorTo Methods the vectors from the center of the circle to two points are obtained respectively .

Vector3d xvector = new Vector3d(1, 0, 0);

Create a X The unit vector of the direction

double startAngle = cs.Y > 0 ? xvector.GetAngleTo(cs) : -xvector.GetAngleTo(cs);
double endAngle = ce.Y > 0 ? xvector.GetAngleTo(ce) : -xvector.GetAngleTo(ce);

adopt GetAngleTo Get the angle between two vectors （ Radian value ）, because GetAngleTo The included angle obtained （ This is the radian system ） Are positive , Take its negative value through judgment , You can draw this arc

Pictured above , Red thread 、 Green line and X The included angles of the shafts are 42°,GetAngleTo The values obtained are 42° The radian value of （ Comes at a time ）, So in order to distinguish , Make a judgment ,startPoint or endPoint Of Y When the coordinate is negative, a negative radian value is returned .

Encapsulate the code page that created the arc above into AddEnityTool.cs in

First, judge X The included angle of the shaft is X The code above or below the axis is encapsulated in BaseTool.cs in

        /// <summary>
        ///  Get two points in a straight line to X The Angle between the axes （ There are positive and negative ）
        /// </summary>
        /// <param name="startPoint"> The starting point </param>
        /// <param name="endPoint"> End </param>
        /// <returns></returns>
        public static double GetAngleToXaxis(Point3d startPoint, Point3d endPoint) 
        {
    
            // Declare a relationship with X A vector with parallel axes 
            Vector3d temp = new Vector3d(1, 0, 0);
            // Get the vector from start to end 
            Vector3d VsToe = startPoint.GetVectorTo(endPoint);
            return VsToe.Y > 0 ? temp.GetAngleTo(VsToe) : -temp.GetAngleTo(VsToe);
        }

Encapsulated in the GetAngleToXaxis Method

The three points given are not prevented from being on the same straight line , A judgment condition is also added to BaseTool.cs in

        /// <summary>
        ///  Judge whether the three points are on the same straight line 
        /// </summary>
        /// <param name="firstPoint"> The first point </param>
        /// <param name="secondPoint"> Second points </param>
        /// <param name="thirdPoint"> The third point </param>
        /// <returns></returns>
        public static bool IsOnOneLine(Point3d firstPoint, Point3d secondPoint, Point3d thirdPoint)
        {
    
            Vector3d v21 = secondPoint.GetVectorTo(firstPoint);
            Vector3d v23 = secondPoint.GetVectorTo(thirdPoint);
            if (v21.GetAngleTo(v23) == 0 || v21.GetAngleTo(v23) == Math.PI)
            {
    
                return true;
            }
            else
            {
    
                return false;
            }
        }

Encapsulated in the IsOnOneLine Method

AddEnityTool.cs In the code

        /// <summary>
        ///  Create an arc through three points 
        /// </summary>
        /// <param name="db"> Graphic database </param>
        /// <param name="startPoint"> The starting point </param>
        /// <param name="pointOnArc"> Point on arc </param>
        /// <param name="endPoint"> End </param>
        /// <returns></returns>
		public static object AddArcToModelSpace(Database db, Point3d startPoint, Point3d pointOnArc, Point3d endPoint)
        {
    
            // First judge whether the three points are on the same straight line 
            if (BaseTool.IsOnOneLine(startPoint, pointOnArc, endPoint))
            {
    
                return ObjectId.Null;
            }
            CircularArc3d cArc = new CircularArc3d(startPoint, pointOnArc, endPoint);
            Arc arc = new Arc(cArc.Center, cArc.Radius, BaseTool.GetAngleToXaxis(cArc.Center,startPoint), BaseTool.GetAngleToXaxis(cArc.Center,endPoint));
            // Add graphics database 
            return AddEnityTool.AddEnityToModelSpace(db,arc);
        }

Through the center of the circle 、 The starting point 、 Draw a circle with included angles （AddEnityTool.cs）

        /// <summary>
        ///  Through the center 、 The starting point 、 Draw a circle with included angles 
        /// </summary>
        /// <param name="db"> Graphic database </param>
        /// <param name="center"> center of a circle </param>
        /// <param name="startPoint"> The starting point </param>
        /// <param name="degree"> Angle </param>
        /// <returns>ObjectId</returns>
        public static ObjectId AddArcToModelSpace(Database db, Point3d center, Point3d startPoint, double degree) 
        {
    
            // Get the radius 
            double radius = BaseTool.GetDistanceBetweenTwoPoint(center, startPoint);
            // Get the starting angle 
            double startAngle = BaseTool.GetAngleToXaxis(center, startPoint);
            // Declare an arc object 
            Arc arc = new Arc(center, radius, startAngle, startAngle + BaseTool.DegreeToAngle(degree));
            return AddEnityTool.AddEnityToModelSpace(db, arc);
        }

The code to obtain the radius is as follows （BaseTool.cs）

        /// <summary>
        ///  Get the distance between two points 
        /// </summary>
        /// <param name="point1"></param>
        /// <param name="point2"></param>
        /// <returns></returns>
        public static double GetDistanceBetweenTwoPoint(Point3d point1, Point3d point2) 
        {
    
            return Math.Sqrt((point1.X - point2.X) * (point1.X - point2.X) + (point1.Y - point2.Y) * (point1.Y - point2.Y) + (point1.Z - point2.Z) * (point1.Z - point2.Z));
        }