Multiple Fixes

src/CSG/Geometry/Cube.cs

@@ -31,10 +31,10 @@ public static void CreateSolid(this IGeometryBuilder builder, Vector3 size)
                 builder.AddIndex(builder.CurrentVertex + 2);
                 builder.AddIndex(builder.CurrentVertex + 3);
 
-                builder.AddVertex(((normal - side1 - side2) / 2.0f) * size, normal, Vector2.Zero);
-                builder.AddVertex(((normal - side1 + side2) / 2.0f) * size, normal, Vector2.UnitX);
-                builder.AddVertex(((normal + side1 + side2) / 2.0f) * size, normal, Vector2.One);
-                builder.AddVertex(((normal + side1 - side2) / 2.0f) * size, normal, Vector2.UnitY);
+                builder.AddVertex(((normal - side1 - side2)) * size, normal, Vector2.Zero);
+                builder.AddVertex(((normal - side1 + side2)) * size, normal, Vector2.UnitX);
+                builder.AddVertex(((normal + side1 + side2)) * size, normal, Vector2.One);
+                builder.AddVertex(((normal + side1 - side2)) * size, normal, Vector2.UnitY);
             }
         }
     }

src/CSG/Geometry/Cylinder.cs

@@ -13,37 +13,61 @@ public static void CreateSolid(this IGeometryBuilder builder, float radius, int
 
         public static void CreateSolid(this IGeometryBuilder builder, Vector3 start, Vector3 end, float radius, int tessellation)
         {
-            builder.AddVertex(start * 0.5f, start);
-            builder.AddVertex(-end * 0.5f, -end);
+            var dir = start - end;
+            if (dir == Vector3.Zero)
+            {
+                dir = new Vector3(1, 0, 0);
+            }
+            dir = Vector3.Normalize(dir);
+
+            builder.AddVertex(start, dir);
+            builder.AddVertex(end, -dir);
+
+            var sTop = 0;
+            var sBottom = 1;
+            var sEdgeTop = 2;
+            var sEdgeBottom = 3;
+
+            var stride = 4;
+
+            int getIndex(int i, int offset)
+            {
+                return 2 + (((i * stride) + offset) % (tessellation * stride));
+            }
+
+            var perp = Vector3.Normalize(Vector3.Cross(new Vector3(dir.Z, dir.X, dir.Y), dir));
 
-            float diameter = radius / 2.0f;
             for (int i = 0; i < tessellation; ++i)
             {
                 float angle = i * Algorithms.Helpers.TwoPi / tessellation;
 
-                float dx = MathF.Cos(angle);
-                float dz = MathF.Sin(angle);
+                var normal = Vector3.Transform(perp, Quaternion.CreateFromAxisAngle(dir, angle));
+                var rotated = normal * radius;
 
-                Vector3 normal = new Vector3(dx, 0.0f, dz);
-
-                builder.AddVertex(normal + (diameter * start), normal);
-                builder.AddVertex(normal - (diameter * start), normal);
+                builder.AddVertex(rotated + start, dir); // Top surface
+                builder.AddVertex(rotated + end, -dir); // Bottom surface
+                builder.AddVertex(rotated + start, normal); // Top edge
+                builder.AddVertex(rotated + end, normal); // Bottom edge
 
+                // Top face
                 builder.AddIndex(0);
-                builder.AddIndex(2 + (i * 2));
-                builder.AddIndex(2 + (((i * 2) + 2) % (tessellation * 2)));
-
-                builder.AddIndex(2 + (i * 2));
-                builder.AddIndex(2 + (i * 2) + 1);
-                builder.AddIndex(2 + (((i * 2) + 2) % (tessellation * 2)));
+                builder.AddIndex(getIndex(i + 1, sTop));
+                builder.AddIndex(getIndex(i, sTop));
 
+                // Bottom face
                 builder.AddIndex(1);
-                builder.AddIndex(2 + (((i * 2) + 3) % (tessellation * 2)));
-                builder.AddIndex(2 + (i * 2) + 1);
+                builder.AddIndex(getIndex(i, sBottom));
+                builder.AddIndex(getIndex(i + 1, sBottom));
+
+                // Side face 1
+                builder.AddIndex(getIndex(i, sEdgeTop));
+                builder.AddIndex(getIndex(i + 1, sEdgeBottom));
+                builder.AddIndex(getIndex(i, sEdgeBottom));
 
-                builder.AddIndex(2 + (i * 2) + 1);
-                builder.AddIndex(2 + (((i * 2) + 3) % (tessellation * 2)));
-                builder.AddIndex(2 + (((i * 2) + 2) % (tessellation * 2)));
+                // Side face 2
+                builder.AddIndex(getIndex(i + 1, sEdgeBottom));
+                builder.AddIndex(getIndex(i, sEdgeTop));
+                builder.AddIndex(getIndex(i + 1, sEdgeTop));
             }
         }
     }

src/CSG/Geometry/Sphere.cs

@@ -17,7 +17,7 @@ public static void CreateSolid(this IGeometryBuilder builder, float radius, int
             int horizontalSegments = tessellation * 2;
 
             // Start with a single vertex at the bottom of the sphere.
-            builder.AddVertex(Vector3.UnitY, -Vector3.UnitY);
+            builder.AddVertex(-Vector3.UnitY * radius, -Vector3.UnitY * radius);
 
             // Create rings of vertices at progressively higher latitudes.
             for (int i = 0; i < verticalSegments - 1; ++i)
@@ -42,7 +42,7 @@ public static void CreateSolid(this IGeometryBuilder builder, float radius, int
             }
 
             // Finish with a single vertex at the top of the sphere.
-            builder.AddVertex(Vector3.UnitY, Vector3.UnitY);
+            builder.AddVertex(Vector3.UnitY * radius, Vector3.UnitY * radius);
 
             // Create a fan connecting the bottom vertex to the bottom latitude ring.
             for (int i = 0; i < horizontalSegments; ++i)

src/CSG/Shape.cs

@@ -110,31 +110,31 @@ protected Shape(SerializationInfo info, StreamingContext context)
         /// <param name="other"></param>
         /// <returns></returns>
         public GeneratedShape Do(ShapeOperation operation, Shape other)
-            => Do(operation, this, other);
+            => Do(operation, other, this);
 
         /// <summary>
         /// Perform a <see cref="ShapeOperation.Union"/> operation with <paramref name="other"/> shape.
         /// </summary>
         /// <param name="other"></param>
         /// <returns></returns>
         public GeneratedShape Union(Shape other)
-            => Union(this, other);
+            => Union(other, this);
 
         /// <summary>
         /// Perform a <see cref="ShapeOperation.Subtract"/> operation with <paramref name="other"/> shape.
         /// </summary>
         /// <param name="other"></param>
         /// <returns></returns>
         public GeneratedShape Subtract(Shape other)
-            => Subtract(this, other);
+            => Subtract(other, this);
 
         /// <summary>
         /// Perform a <see cref="ShapeOperation.Intersect"/> operation with <paramref name="other"/> shape.
         /// </summary>
         /// <param name="other"></param>
         /// <returns></returns>
         public GeneratedShape Intersect(Shape other)
-            => Intersect(this, other);
+            => Intersect(other, this);
 
         /// <summary>
         /// Create polygons of the <see cref="Shape"/>.