Line implements Interface IHasArcLength

Author: jamesbradleym

CHANGELOG.md

@@ -33,6 +33,7 @@
 - `Arc` is now parameterized 0->2Pi
 - `Line` now inherits from `TrimmedCurve<InfiniteLine>`.
 - `Line` is now parameterized 0->length.
+- `Line` now implements the `IHasArcLength` interface
 - `Bezier` now inherits from `BoundedCurve`.
 - `Polyline` is now parameterized 0->length.
 - `Circle` is now parameterized 0->2Pi.

Elements/src/Elements.csproj

@@ -10,7 +10,7 @@
     <Summary>The Elements library provides object types for generating the built environment.</Summary>
     <PackageProjectUrl>https://github.com/hypar-io/elements</PackageProjectUrl>
     <RepositoryUrl>https://github.com/hypar-io/elements</RepositoryUrl>
-    <Version>$(Version)</Version>
+    <Version>21.21.21</Version>
     <SatelliteResourceLanguages>en</SatelliteResourceLanguages>
   </PropertyGroup>
   <ItemGroup>

Elements/src/Geometry/Line.cs

@@ -4,6 +4,7 @@
 using System.Linq;
 using Newtonsoft.Json;
 using Elements.Spatial;
+using Elements.Geometry.Interfaces;
 
 namespace Elements.Geometry
 {
@@ -15,7 +16,7 @@ namespace Elements.Geometry
     /// [!code-csharp[Main](../../Elements/test/LineTests.cs?name=example)]
     /// </example>
     /// TODO: Rename this class to LineSegment
-    public class Line : TrimmedCurve<InfiniteLine>, IEquatable<Line>
+    public class Line : TrimmedCurve<InfiniteLine>, IEquatable<Line>, IHasArcLength
     {
         /// <summary>
         /// The domain of the curve.
@@ -123,6 +124,48 @@ public override Vector3 PointAt(double u)
             return this.BasisCurve.PointAt(u);
         }
 
+        /// <summary>
+        /// The mid point of the curve.
+        /// </summary>
+        /// <returns>The length based midpoint.</returns>
+        public virtual Vector3 MidPoint()
+        {
+            return PointAtNormalizedLength(0.5);
+        }
+
+        /// <summary>
+        /// Returns the point on the line corresponding to the specified length value.
+        /// </summary>
+        /// <param name="length">The length value along the line.</param>
+        /// <returns>The point on the line corresponding to the specified length value.</returns>
+        /// <exception cref="ArgumentException">Thrown when the specified length is out of range.</exception>
+        public virtual Vector3 PointAtLength(double length)
+        {
+            double totalLength = ArcLength(this.Domain.Min, this.Domain.Max); // Calculate the total length of the Line
+
+            if (length < 0 || length > totalLength)
+            {
+                throw new ArgumentException("The specified length is out of range.");
+            }
+            var lengthParameter = length / totalLength;
+            return this.PointAtNormalized(lengthParameter);
+        }
+
+        /// <summary>
+        /// Returns the point on the line corresponding to the specified normalized length-based parameter value.
+        /// </summary>
+        /// <param name="parameter">The normalized length-based parameter value, ranging from 0 to 1.</param>
+        /// <returns>The point on the line corresponding to the specified normalized length-based parameter value.</returns>
+        /// <exception cref="ArgumentException">Thrown when the specified parameter is out of range.</exception>
+        public virtual Vector3 PointAtNormalizedLength(double parameter)
+        {
+            if (parameter < 0 || parameter > 1)
+            {
+                throw new ArgumentException("The specified parameter is out of range.");
+            }
+            return PointAtLength(parameter * this.ArcLength(this.Domain.Min, this.Domain.Max));
+        }
+
         /// <inheritdoc/>
         public override Curve Transformed(Transform transform)
         {
@@ -541,38 +584,79 @@ public static bool PointOnLine(Vector3 point, Vector3 start, Vector3 end, bool i
             return false;
         }
 
+        // /// <summary>
+        // /// Divide the line into as many segments of the provided length as possible.
+        // /// </summary>
+        // /// <param name="l">The length.</param>
+        // /// <param name="removeShortSegments">A flag indicating whether segments shorter than l should be removed.</param>
+        // public List<Line> DivideByLength(double l, bool removeShortSegments = false)
+        // {
+        //     var len = this.Length();
+        //     if (l > len)
+        //     {
+        //         return new List<Line>() { new Line(this.Start, this.End) };
+        //     }
+
+        //     var total = 0.0;
+        //     var d = this.Direction();
+        //     var lines = new List<Line>();
+        //     while (total + l <= len)
+        //     {
+        //         var a = this.Start + d * total;
+        //         var b = a + d * l;
+        //         lines.Add(new Line(a, b));
+        //         total += l;
+        //     }
+        //     if (total < len && !removeShortSegments)
+        //     {
+        //         var a = this.Start + d * total;
+        //         if (!a.IsAlmostEqualTo(End))
+        //         {
+        //             lines.Add(new Line(a, End));
+        //         }
+        //     }
+        //     return lines;
+        // }
+
         /// <summary>
-        /// Divide the line into as many segments of the provided length as possible.
+        /// Divides the line into segments of the specified length.
         /// </summary>
-        /// <param name="l">The length.</param>
-        /// <param name="removeShortSegments">A flag indicating whether segments shorter than l should be removed.</param>
-        public List<Line> DivideByLength(double l, bool removeShortSegments = false)
+        /// <param name="divisionLength">The desired length of each segment.</param>
+        /// <returns>A list of points representing the segments.</returns>
+        public Vector3[] DivideByLength(double divisionLength)
         {
-            var len = this.Length();
-            if (l > len)
+            var segments = new List<Vector3>();
+
+            if (this.ArcLength(this.Domain.Min, this.Domain.Max) < double.Epsilon)
             {
-                return new List<Line>() { new Line(this.Start, this.End) };
+                // Handle invalid line with insufficient length
+                return new Vector3[0];
             }
 
-            var total = 0.0;
-            var d = this.Direction();
-            var lines = new List<Line>();
-            while (total + l <= len)
+            var currentProgression = 0.0;
+            segments = new List<Vector3> { this.Start };
+
+            // currentProgression from last segment before hitting end
+            if (currentProgression != 0.0)
             {
-                var a = this.Start + d * total;
-                var b = a + d * l;
-                lines.Add(new Line(a, b));
-                total += l;
+                currentProgression -= divisionLength;
             }
-            if (total < len && !removeShortSegments)
+            while (this.ArcLength(this.Domain.Min, this.Domain.Max) >= currentProgression + divisionLength)
             {
-                var a = this.Start + d * total;
-                if (!a.IsAlmostEqualTo(End))
-                {
-                    lines.Add(new Line(a, End));
-                }
+                segments.Add(this.PointAt(currentProgression + divisionLength));
+                currentProgression += divisionLength;
             }
-            return lines;
+            // Set currentProgression from divisionLength less distance from last segment point
+            currentProgression = divisionLength - segments.LastOrDefault().DistanceTo(this.End);
+
+            // Add the last vertex of the polyline as the endpoint of the last segment if it
+            // is not already part of the list
+            if (!segments.LastOrDefault().IsAlmostEqualTo(this.End))
+            {
+                segments.Add(this.End);
+            }
+
+            return segments.ToArray();
         }
 
         /// <summary>
@@ -925,7 +1009,7 @@ public double DistanceTo(Line other)
             // line vectors are not collinear, their directions share the common plane.
             else
             {
-                // dStartStart length is distance to the common plane. 
+                // dStartStart length is distance to the common plane.
                 dStartStart = dStartStart.ProjectOnto(cross);
                 Vector3 vStartStart = other.Start + dStartStart - this.Start;
                 Vector3 vStartEnd = other.Start + dStartStart - this.End;
@@ -1028,8 +1112,8 @@ public List<Line> Trim(Polygon polygon, out List<Line> outsideSegments, bool inc
                 var B = intersectionsOrdered[i + 1];
                 if (A.IsAlmostEqualTo(B)) // skip duplicate points
                 {
-                    // it's possible that A is outside, but B is at an edge, even 
-                    // if they are within tolerance of each other. 
+                    // it's possible that A is outside, but B is at an edge, even
+                    // if they are within tolerance of each other.
                     // This can happen due to floating point error when the point is almost exactly
                     // epsilon distance from the edge.
                     // so if we have duplicate points, we have to update the containment value.

Elements/src/Geometry/Polyline.cs

@@ -85,8 +85,6 @@ public virtual Line[] Segments()
             return SegmentsInternal(this.Vertices);
         }
 
-
-
         /// <summary>
         /// The mid point of the curve.
         /// </summary>

Elements/test/LineTests.cs

@@ -163,11 +163,11 @@ public void DivideIntoEqualSegmentsSingle()
         public void DivideByLength()
         {
             var l = new Line(Vector3.Origin, new Vector3(5, 0));
-            var segments = l.DivideByLength(1.1, true);
-            Assert.Equal(4, segments.Count);
+            var segments = l.DivideByLength(1.1);
+            Assert.Equal(6, segments.Count());
 
-            var segments1 = l.DivideByLength(1.1);
-            Assert.Equal(5, segments1.Count);
+            var segments1 = l.DivideByLength(2);
+            Assert.Equal(4, segments1.Count());
         }
 
         [Fact]
@@ -650,6 +650,17 @@ public void GetParameterAt()
             var expectedVector = line.PointAt(uValue);
             Assert.InRange(uValue, 0, line.Length());
             Assert.True(vector.IsAlmostEqualTo(expectedVector));
+
+            var parameter = 0.5;
+            var testParameterMidpoint = line.PointAtNormalizedLength(parameter);
+            Assert.True(testParameterMidpoint.IsAlmostEqualTo(middle));
+
+            var midlength = line.Length() * parameter;
+            var testLengthMidpoint = line.PointAtLength(midlength);
+            Assert.True(testLengthMidpoint.IsAlmostEqualTo(testParameterMidpoint));
+
+            var midpoint = line.MidPoint();
+            Assert.True(midpoint.IsAlmostEqualTo(testLengthMidpoint));
         }
 
         [Theory]
@@ -1110,7 +1121,7 @@ public void LineDistancePointsOnSkewLines()
             Assert.Equal(delta.Length(), (new Line(pt12, pt11)).DistanceTo(new Line(pt21, pt22)), 12);
             Assert.Equal(delta.Length(), (new Line(pt12, pt11)).DistanceTo(new Line(pt22, pt21)), 12);
             //The segments (pt12, pt13) and (pt21, pt22) does not intersect.
-            //The shortest distance is from an endpoint to another segment - difference between lines plus between endpoints. 
+            //The shortest distance is from an endpoint to another segment - difference between lines plus between endpoints.
             var expected = (q12 * v1).DistanceTo(new Line(delta + q21 * v2, delta + q22 * v2));
             Assert.Equal(expected, (new Line(pt12, pt13)).DistanceTo(new Line(pt21, pt22)), 12);
             Assert.Equal(expected, (new Line(pt12, pt13)).DistanceTo(new Line(pt22, pt21)), 12);

Elements/test/PolylineTests.cs

@@ -270,7 +270,6 @@ public void GetParameterAt()
             var parameter = 0.5;
             var testMidpoint = new Vector3(5.0, 14.560525, 0); // Midpoint
             var testParameterMidpoint = polyline.PointAtNormalizedLength(parameter);
-            var t = testParameterMidpoint.IsAlmostEqualTo(testMidpoint);
             Assert.True(testParameterMidpoint.IsAlmostEqualTo(testMidpoint));
 
             var midlength = polyline.Length() * parameter;