wire rail: preserve resolved materials during mesh regeneration

VisualPinball.Unity/VisualPinball.Unity.Test/VPT/WireRail/WireRailComponentTests.cs

@@ -34,6 +34,54 @@ public void TearDown()
 			Undo.ClearAll();
 		}
 
+		[Test]
+		public void ShouldKeepResolvedRenderMaterialAcrossActivationAndMeshRebuilds()
+		{
+			var go = new GameObject("Wire Rail"); go.SetActive(false);
+			var imported = new Material(Shader.Find("Hidden/InternalErrorShader"));
+			var resolved = new Material(imported);
+			try {
+				var component = go.AddComponent<WireRailComponent>();
+				var renderer = component.SplineContainer.GetComponent<MeshRenderer>();
+				renderer.sharedMaterial = imported;
+				component.RebuildRenderGeometry();
+				// Package profiles replace glTF placeholders while the table is inactive.
+				renderer.sharedMaterial = resolved;
+				go.SetActive(true);
+				Assert.That(renderer.sharedMaterial, Is.SameAs(resolved));
+				component.RebuildRenderGeometry();
+				Assert.That(renderer.sharedMaterial, Is.SameAs(resolved));
+				Object.DestroyImmediate(renderer);
+				component.RebuildRenderGeometry();
+				Assert.That(component.SplineContainer.GetComponent<MeshRenderer>().sharedMaterial, Is.SameAs(resolved));
+			} finally {
+				Object.DestroyImmediate(go); Object.DestroyImmediate(imported); Object.DestroyImmediate(resolved);
+			}
+		}
+		[TestCase(false)]
+		[TestCase(true)]
+		public void ShouldApplyAnExplicitRenderMaterialChangeAfterAssigningTheRenderer(bool afterDomainReload)
+		{
+			var go = new GameObject("Wire Rail");
+			var original = new Material(Shader.Find("Hidden/InternalErrorShader"));
+			var chosen = new Material(original);
+			try {
+				var component = go.AddComponent<WireRailComponent>();
+				var renderer = component.SplineContainer.GetComponent<MeshRenderer>();
+				renderer.sharedMaterial = original;
+				component.RebuildRenderGeometry();
+				// The inspector edits this serialized choice, rather than the generated renderer.
+				typeof(WireRailComponent).GetField("_renderMaterial", BindingFlags.Instance | BindingFlags.NonPublic).SetValue(component, chosen);
+				if (afterDomainReload) {
+					// Unity retains the serialized choice but clears assignment tracking on reload.
+					typeof(WireRailComponent).GetField("_lastAssignedRenderMaterial", BindingFlags.Instance | BindingFlags.NonPublic).SetValue(component, null);
+				}
+				component.RebuildRenderGeometry();
+				Assert.That(renderer.sharedMaterial, Is.SameAs(chosen));
+			} finally {
+				Object.DestroyImmediate(go); Object.DestroyImmediate(original); Object.DestroyImmediate(chosen);
+			}
+		}
 		[Test]
 		public void ShouldCreateAThreeDimensionalVpxSpline()
 		{

VisualPinball.Unity/VisualPinball.Unity/VPT/WireRail/WireRailComponent.cs

@@ -1763,6 +1763,7 @@ public class WireRailComponent : MonoBehaviour, ICollidableComponent, IPackable
 		[NonSerialized] private Vector3[] _colliderEdgeVertices = Array.Empty<Vector3>();
 		[NonSerialized] private int _colliderTopologyRetryCount;
 		[NonSerialized] private bool _rebuildingGeneratedMeshes;
+		[NonSerialized] private Material _lastAssignedRenderMaterial;
 		[NonSerialized] private bool _collidersDirty = true;
 		[NonSerialized] private bool _colliderGeometryDirty = true;
 		[NonSerialized] private int _renderGeometryVersion;
@@ -3626,16 +3627,19 @@ private void AssignRenderMaterial(MeshRenderer renderer, bool adoptExisting)
 		{
 			var pipeline = GraphicsSettings.currentRenderPipeline;
 			var pipelineDefault = pipeline ? pipeline.defaultMaterial : GetBuiltinDefaultMaterial();
-			if (adoptExisting && !_renderMaterial && renderer.sharedMaterial
-				&& renderer.sharedMaterial != pipelineDefault) {
+			if (adoptExisting && renderer.sharedMaterial
+				&& renderer.sharedMaterial != pipelineDefault
+				&& (!_renderMaterial || _lastAssignedRenderMaterial && renderer.sharedMaterial != _lastAssignedRenderMaterial)) {
 				// The renderer arrived with a material of its own, e.g. restored from a
-				// package; that is the author's choice, not something to overwrite.
+				// package, or a material resolver replaced our last assignment. Keep that
+				// resolved material when activation or a spline edit rebuilds the mesh.
 				_renderMaterial = renderer.sharedMaterial;
 			}
 			var material = _renderMaterial ? _renderMaterial : pipelineDefault;
 			if (renderer.sharedMaterial != material) {
 				renderer.sharedMaterial = material;
 			}
+			_lastAssignedRenderMaterial = material;
 		}
 
 		private static Material GetBuiltinDefaultMaterial()