Generate face normals in pixel shader

.gitignore

@@ -25,3 +25,5 @@ libCesiumForUnityNative-*.so.meta
 libCesiumForUnityNative-*.dylib
 libCesiumForUnityNative-*.dylib.meta
 Documentation~/Reference/
+package-lock.json
+

CHANGES.md

@@ -6,6 +6,11 @@
 
 - Added option to ignore the `KHR_material_unlit` extension to force default lighting on tilesets. 
 
+##### Breaking Changes :mega:
+
+- Flat normals are now computed in `CesiumDefaultTilesetShader` to avoid duplicating vertices as tiles are loaded. Existing copies of this shader should incorporate this logic using the boolean `computeFlatNormals` property to maintain a correct appearance.
+
+
 ## v1.17.0 - 2025-08-01
 
 ##### Additions :tada:

Editor/Cesium3DTilesetEditor.cs

@@ -35,6 +35,7 @@ public class Cesium3DTilesetEditor : Editor
         //private SerializedProperty _useLodTransitions;
         //private SerializedProperty _lodTransitionLength;
         private SerializedProperty _generateSmoothNormals;
+        private SerializedProperty _generateTangents;
 
         private SerializedProperty _pointCloudShading;
 
@@ -84,6 +85,9 @@ private void OnEnable()
             //    this.serializedObject.FindProperty("_lodTransitionLength");
             this._generateSmoothNormals =
                 this.serializedObject.FindProperty("_generateSmoothNormals");
+            this._generateTangents =
+                this.serializedObject.FindProperty("_generateTangents");
+
             this._ignoreKhrMaterialsUnlit = this.serializedObject.FindProperty("_ignoreKhrMaterialsUnlit");
 
             this._pointCloudShading = this.serializedObject.FindProperty("_pointCloudShading");
@@ -422,13 +426,19 @@ private void DrawRenderProperties()
                 "Generate Smooth Normals",
                 "Whether to generate smooth normals when normals are missing in the glTF." +
                 "\n\n" +
-                "According to the glTF spec: \"When normals are not specified, client " +
-                "implementations should calculate flat normals.\" However, calculating flat " +
-                "normals requires duplicating vertices. This option allows the glTFs to be " +
-                "rendered with smooth normals instead when the original glTF is missing normals.");
+                "This option allows glTFs to be rendered with smooth normals when the original glTF " +
+                "is missing normals. If this option is not enabled and normals are missing, " +
+                "flat normals will be generated in the shader. "
+                );
             EditorGUILayout.PropertyField(this._generateSmoothNormals, generateSmoothNormalsContent);
 
-            var ignoreKhrMaterialsUnlit = new GUIContent(
+            var generateTangentsContent = new GUIContent(
+                "Generate Tangents",
+                "Whether to generate per-vertex tangets if they are missing in the source glTF."
+            );
+            EditorGUILayout.PropertyField(this._generateTangents, generateTangentsContent);
+
+            var ignoreKhrMaterialsUnlitContent = new GUIContent(
                 "Ignore KHR_materials_unlit",
                 "Whether to ignore the KHR_materials_unlit extension on the glTF tiles in "+
                 "this tileset, if it exists, and instead render with standard lighting and "+
@@ -439,7 +449,7 @@ private void DrawRenderProperties()
                 "tilesets because lighting and shadows are already baked into their "+
                 "textures. "
             );
-            EditorGUILayout.PropertyField(this._ignoreKhrMaterialsUnlit, ignoreKhrMaterialsUnlit);
+            EditorGUILayout.PropertyField(this._ignoreKhrMaterialsUnlit, ignoreKhrMaterialsUnlitContent);
         }
 
         private void DrawPointCloudShadingProperties()

Runtime/Cesium3DTileset.cs

@@ -574,10 +574,8 @@ public Material opaqueMaterial
         /// Whether to generate smooth normals when normals are missing in the glTF.
         /// </summary>
         /// <remarks>
-        /// According to the glTF spec: "When normals are not specified, client
-        /// implementations should calculate flat normals." However, calculating flat
-        /// normals requires duplicating vertices. This option allows the glTFs to be rendered
-        /// with smooth normals instead when the original glTF is missing normals.
+        /// This option allows the glTFs to be rendered with smooth normals instead when the original glTF is missing normals. 
+        /// If normals are missing and this option is not enabled, flat normals will be generated in the shader. 
         /// </remarks>
         public bool generateSmoothNormals
         {
@@ -589,6 +587,31 @@ public bool generateSmoothNormals
             }
         }
 
+        [SerializeField]
+        private bool _generateTangents = false;
+
+        /// <summary>
+        /// Whether to generate per-vertex tangents when tangents are missing in the glTF.
+        /// </summary>
+        /// <remarks>
+        /// The glTF 2.0 specification suggests that tangents should be generated when they 
+        /// are missing. 
+        /// "When tangents are not specified, client implementations SHOULD calculate tangents using 
+        /// default MikkTSpace algorithms with the specified vertex positions, normals, and texture 
+        /// coordinates associated with the normal texture."
+        /// </remarks>
+        /// <seealso cref="https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html"/>
+
+        public bool generateTangents
+        {
+            get => _generateTangents;
+            set
+            {
+                this._generateSmoothNormals = value;
+                this.RecreateTileset();
+            }
+        }
+
         [SerializeField]
         private bool _ignoreKhrMaterialsUnlit = false;
 

Runtime/ConfigureReinterop.cs

@@ -77,7 +77,7 @@ public void ExposeToCPP()
             int pixelWidth = c.pixelWidth;
             float aspect = c.aspect;
             bool isOrtho = c.orthographic;
-            float orthoSize = c.orthographicSize;            
+            float orthoSize = c.orthographicSize;
             //IFormattable f = new Vector3();
             //IEquatable<Vector3> f2 = new Vector3();
 
@@ -185,6 +185,14 @@ public void ExposeToCPP()
             meshFilter.mesh = mesh;
             meshFilter.sharedMesh = mesh;
 
+            Debug.Log("Hello world");
+
+            mesh.RecalculateTangents();
+            var tangents = mesh.tangents;
+            var normals = mesh.normals;
+            mesh.RecalculateNormals();
+
+
             Resources.Load<Material>("name");
 
             byte b;
@@ -236,7 +244,7 @@ public void ExposeToCPP()
             string e = request.error;
             string method = request.method;
             string url = request.url;
-            if (request.result == UnityWebRequest.Result.Success) { };
+            if (request.result == UnityWebRequest.Result.Success) { }
             request.downloadHandler = new NativeDownloadHandler();
             request.SetRequestHeader("name", "value");
             request.GetResponseHeader("name");
@@ -279,6 +287,7 @@ public void ExposeToCPP()
             //tileset.useLodTransitions = tileset.useLodTransitions;
             //tileset.lodTransitionLength = tileset.lodTransitionLength;
             tileset.generateSmoothNormals = tileset.generateSmoothNormals;
+            tileset.generateTangents = tileset.generateTangents;
             tileset.ignoreKhrMaterialsUnlit = tileset.ignoreKhrMaterialsUnlit;
             tileset.createPhysicsMeshes = tileset.createPhysicsMeshes;
             tileset.suspendUpdate = tileset.suspendUpdate;
@@ -289,6 +298,7 @@ public void ExposeToCPP()
             tileset.ionServer = tileset.ionServer;
             tileset.RecreateTileset();
 
+
             GraphicsFormat gfxFmt = GraphicsFormat.RGB_ETC_UNorm;
             FormatUsage fmtUsage = FormatUsage.Sample;
             SystemInfo.IsFormatSupported(gfxFmt, fmtUsage);

Runtime/Resources/CesiumDefaultTilesetMaterial.mat

@@ -21,19 +21,17 @@ Material:
   m_PrefabInstance: {fileID: 0}
   m_PrefabAsset: {fileID: 0}
   m_Name: CesiumDefaultTilesetMaterial
-  m_Shader: {fileID: -6465566751694194690, guid: 407c0cff68611ac46a65eec87a5203f5,
+  m_Shader: {fileID: -6465566751694194690, guid: f1bf6a52c1d9b4896bcefbee4a1432af,
     type: 3}
+  m_Parent: {fileID: 0}
+  m_ModifiedSerializedProperties: 0
   m_ValidKeywords:
   - _ALPHATEST_ON
-  - _BUILTIN_ALPHATEST_ON
-  - _BUILTIN_AlphaClip
-  - _DISABLE_SSR_TRANSPARENT
-  - _DOUBLESIDED_ON
   m_InvalidKeywords: []
   m_LightmapFlags: 2
   m_EnableInstancingVariants: 0
   m_DoubleSidedGI: 1
-  m_CustomRenderQueue: 2450
+  m_CustomRenderQueue: -1
   stringTagMap:
     MotionVector: User
     RenderType: TransparentCutout
@@ -43,6 +41,7 @@ Material:
   - TransparentBackface
   - RayTracingPrepass
   - MOTIONVECTORS
+  m_LockedProperties: 
   m_SavedProperties:
     serializedVersion: 3
     m_TexEnvs:
@@ -101,7 +100,7 @@ Material:
     - _AlphaCutoffEnable: 1
     - _AlphaDstBlend: 0
     - _AlphaSrcBlend: 1
-    - _AlphaToMask: 0
+    - _AlphaToMask: 1
     - _AlphaToMaskInspectorValue: 0
     - _BUILTIN_AlphaClip: 1
     - _BUILTIN_Blend: 0
@@ -116,6 +115,7 @@ Material:
     - _BUILTIN_ZWriteControl: 0
     - _Blend: 0
     - _BlendMode: 0
+    - _BlendModePreserveSpecular: 0
     - _CastShadows: 1
     - _ConservativeDepthOffsetEnable: 0
     - _Cull: 0
@@ -168,6 +168,7 @@ Material:
     - _ZWrite: 1
     - _ZWriteControl: 0
     - _baseColorTextureCoordinateIndex: 0
+    - _computeFlatNormals: 0
     - _emissiveTextureCoordinateIndex: 0
     - _metallicRoughnessTextureCoordinateIndex: 0
     - _normalMapScale: 0
@@ -222,4 +223,4 @@ MonoBehaviour:
   m_Script: {fileID: 11500000, guid: d0353a89b1f911e48b9e16bdc9f2e058, type: 3}
   m_Name: 
   m_EditorClassIdentifier: 
-  version: 5
+  version: 7