[UUM-133529] ProBuilder GameObjects not changing back to 3D shapes after Plane/Sprite transition

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Fixed
 
+- [UUM-133529] Fixed an issue where ProBuilder GameObjects could not change back to 3D shapes after being changed to Plane or Sprite.
 - [UUM-133861] Fixed "Look rotation viewing vector is zero" log being spammed when holding shift while using a create tool such as Create Sprite.
 - [UUM-133859] Fixed an issue in URP projects where the Editor would recompile scripts when after a rectangle selection in ProBuilder. 
 - [UUM-133530] Fixed the `Set Double Sided` custom action in the Editor Sample, which was previously remaining disabled.

Runtime/Shapes/ProBuilderShape.cs

@@ -10,6 +10,8 @@
         const string k_HelpUrl = "https://docs.unity3d.com/Packages/com.unity.probuilder@latest";
         const string k_IconPath = "Packages/com.unity.probuilder/Editor Default Resources/Icons/EditableMesh/EditableMesh.png";
 
+        const float k_MinHeight = 0.0001f;
+
         [SerializeReference]
         Shape m_Shape = new Cube();
 
@@ -58,7 +60,7 @@
             {
                 m_EditionBounds.center = m_LocalCenter;
                 m_EditionBounds.size = m_Size;
-                if(Mathf.Abs(m_Size.y) < Mathf.Epsilon)
+                if(Mathf.Abs(m_Size.y) < k_MinHeight)
                     m_EditionBounds.size = new Vector3(m_Size.x, 0f, m_Size.z);
 
                 return m_EditionBounds;
@@ -146,8 +148,12 @@
 
         internal void SetShape(Shape shape)
         {
+            bool wasFlat = m_Shape is Plane || m_Shape is Sprite;
+            bool isFlat = shape is Plane || shape is Sprite;
+
             m_Shape = shape;
-            if(m_Shape is Plane || m_Shape is Sprite)
+
+            if(isFlat)
             {
                 Bounds bounds = new Bounds(m_LocalCenter, size);
                 var newCenter = bounds.center;
@@ -158,6 +164,13 @@
                 size = newSize;
                 m_Size.y = 0;
             }
+            else if(wasFlat && !isFlat)
+            {
+                // Transitioning FROM a 2D shape TO a 3D shape - restore Y dimension
+                if(Mathf.Abs(m_Size.y) < k_MinHeight)
+                    m_Size.y = 1f;
+            }
+
             UpdateShape();
 
             m_UnmodifiedMeshVersion = mesh.versionIndex;