Implement method in BoundingBox to create corresponding Mesh

CadRevealComposer.Tests/BoundingBoxTests.cs

@@ -2,6 +2,7 @@ namespace CadRevealComposer.Tests;
 
 using System.Drawing;
 using System.Numerics;
+using CadRevealComposer.Utils;
 
 public class BoundingBoxTests
 {
@@ -66,4 +67,69 @@ public void Extents_ReturnsSizeInAllDimensions()
         var extents = new Vector3(3, 3, 3);
         Assert.That(boundingBox.Extents, Is.EqualTo(extents));
     }
+
+    [Test]
+    public void CreateBoundingBoxMesh_GivenABoundingBox_ValidateTheOutputMesh()
+    {
+        // Create randomizer
+        var rand = new Random();
+
+        // Create true bounding box, based on random lengths for x, y, z, as well as random position, r
+        var xyz = GenRandomVec3(20.0, -5.0);
+        var r = GenRandomVec3(100.0, 50.0);
+        var trueBoundingBox = new BoundingBox(r - xyz * 0.5f, r + xyz * 0.5f);
+
+        // Create the bounding box mesh (ToBoxMesh is the method we want to test)
+        var boundingBoxMesh = trueBoundingBox.ToBoxMesh(0.01f);
+
+        // Verify that all vertices within the generated mesh is on the true bounding box
+        // (assures we cannot have a "rotated" Mesh with a bounding box matching the true bounding box)
+        const float tolerance = 1.0e-4f;
+        var tolerance3 = new Vector3(tolerance, tolerance, tolerance);
+        foreach (Vector3 p in boundingBoxMesh.Vertices)
+        {
+            Assert.Multiple(() =>
+            {
+                Assert.That(
+                    IsWithinBox(p, new BoundingBox(trueBoundingBox.Min - tolerance3, trueBoundingBox.Max + tolerance3)),
+                    Is.True
+                );
+                Assert.That(
+                    IsWithinBox(p, new BoundingBox(trueBoundingBox.Min + tolerance3, trueBoundingBox.Max - tolerance3)),
+                    Is.False
+                );
+            });
+        }
+
+        // Make sure the bounding box of the Mesh matches the true bounding box
+        var boundingBoxOfMesh = boundingBoxMesh.CalculateAxisAlignedBoundingBox();
+        Assert.That(
+            boundingBoxOfMesh,
+            Is.EqualTo(trueBoundingBox)
+                .Using<BoundingBox>(
+                    (x, y) =>
+                        x.Min.EqualsWithinTolerance(y.Min, tolerance) && x.Max.EqualsWithinTolerance(y.Max, tolerance)
+                )
+        );
+        return;
+
+        // Define lambda functions
+        Vector3 GenRandomVec3(double maxSize, double offset) =>
+            new Vector3(
+                (float)(maxSize * rand.NextDouble() - offset),
+                (float)(maxSize * rand.NextDouble() - offset),
+                (float)(maxSize * rand.NextDouble() - offset)
+            );
+
+        bool IsWithinBox(Vector3 coordinate, BoundingBox bbox)
+        {
+            if (coordinate.X < bbox.Min.X || coordinate.X > bbox.Max.X)
+                return false;
+            if (coordinate.Y < bbox.Min.Y || coordinate.Y > bbox.Max.Y)
+                return false;
+            if (coordinate.Z < bbox.Min.Z || coordinate.Z > bbox.Max.Z)
+                return false;
+            return true;
+        }
+    }
 }

CadRevealComposer/CadRevealNode.cs

@@ -5,6 +5,7 @@ namespace CadRevealComposer;
 using System.Numerics;
 using Primitives;
 using ProtoBuf;
+using Tessellation;
 using Utils;
 
 [ProtoContract(SkipConstructor = true)]
@@ -49,6 +50,36 @@ public Box ToBoxPrimitive(uint treeIndex, Color color)
         return new Box(matrix, treeIndex, color, this);
     }
 
+    /// <summary>
+    /// Creates a Mesh <see cref="Mesh"/> representing the bounding box coordinates.
+    /// </summary>
+    /// <returns>Mesh representing the bounding box.</returns>
+    public Mesh ToBoxMesh(float error)
+    {
+        Vector3[] boundingBoxVertices = new Vector3[8];
+
+        Vector3 d = Max - Min;
+        boundingBoxVertices[0] = Min;
+        boundingBoxVertices[1] = Min + new Vector3(d.X, 0.0f, 0.0f);
+        boundingBoxVertices[2] = Min + new Vector3(0.0f, d.Y, 0.0f);
+        boundingBoxVertices[3] = Min + new Vector3(d.X, d.Y, 0.0f);
+
+        boundingBoxVertices[4] = Min + new Vector3(0.0f, 0.0f, d.Z);
+        boundingBoxVertices[5] = Min + new Vector3(d.X, 0.0f, d.Z);
+        boundingBoxVertices[6] = Min + new Vector3(0.0f, d.Y, d.Z);
+        boundingBoxVertices[7] = Min + new Vector3(d.X, d.Y, d.Z);
+
+        var indices = new List<uint>();
+        indices.AddRange([0, 2, 3, 0, 3, 1]); // Indices for two triangles along the X-Y-near plane of the bounding box
+        indices.AddRange([0, 1, 4, 1, 5, 4]); // Indices for two triangles along the X-Z-near plane of the bounding box
+        indices.AddRange([0, 6, 2, 0, 4, 6]); // Indices for two triangles along the Y-Z-near plane of the bounding box
+        indices.AddRange([3, 2, 6, 3, 6, 7]); // Indices for two triangles along the X-Z-far plane of the bounding box
+        indices.AddRange([3, 5, 1, 3, 7, 1]); // Indices for two triangles along the Y-Z-far plane of the bounding box
+        indices.AddRange([4, 5, 7, 4, 7, 6]); // Indices for two triangles along the X-Y-far plane of the bounding box
+
+        return new Mesh(boundingBoxVertices, indices.ToArray(), error);
+    }
+
     /// <summary>
     /// Check if bounding box of this node is equal to other bounding box
     /// </summary>