Modified vertex buffer generation to include tangents when necessary. Added editor support for forcing tangent generation.

Author: david-lively

Editor/Cesium3DTilesetEditor.cs

@@ -35,6 +35,7 @@ public class Cesium3DTilesetEditor : Editor
         //private SerializedProperty _useLodTransitions;
         //private SerializedProperty _lodTransitionLength;
         private SerializedProperty _generateSmoothNormals;
+        private SerializedProperty _alwaysIncludeTangents;
 
         private SerializedProperty _pointCloudShading;
 
@@ -84,6 +85,8 @@ private void OnEnable()
             //    this.serializedObject.FindProperty("_lodTransitionLength");
             this._generateSmoothNormals =
                 this.serializedObject.FindProperty("_generateSmoothNormals");
+            this._alwaysIncludeTangents =
+                this.serializedObject.FindProperty("_alwaysIncludeTangents");
             this._ignoreKhrMaterialsUnlit = this.serializedObject.FindProperty("_ignoreKhrMaterialsUnlit");
 
             this._pointCloudShading = this.serializedObject.FindProperty("_pointCloudShading");
@@ -428,7 +431,17 @@ private void DrawRenderProperties()
                 "rendered with smooth normals instead when the original glTF is missing normals.");
             EditorGUILayout.PropertyField(this._generateSmoothNormals, generateSmoothNormalsContent);
 
-            var ignoreKhrMaterialsUnlit = new GUIContent(
+            var alwaysIncludeTangents = new GUIContent(
+                "Always Include Tangents",
+                "Whether to generate tangents when they are missing from the glTF." +
+                "According to the glTF spec: \"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.\""
+            );
+            EditorGUILayout.PropertyField(this._alwaysIncludeTangents, alwaysIncludeTangents);
+
+            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 +452,7 @@ 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

@@ -589,6 +589,27 @@ public bool generateSmoothNormals
             }
         }
 
+        [SerializeField]
+        private bool _alwaysIncludeTangents = false;
+        /// <summary>
+        /// Whether to generate tangents when they are missing from the glTF. 
+        /// </summary>
+        /// <remarks>
+        /// According to the glTF spec: "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>
+        public bool alwaysIncludeTangents
+        {
+            get => this._alwaysIncludeTangents;
+            set
+            {
+                this._alwaysIncludeTangents = value;
+                this.RecreateTileset();
+            }
+        }
+
         [SerializeField]
         private bool _ignoreKhrMaterialsUnlit = false;
 

Runtime/ConfigureReinterop.cs

@@ -279,6 +279,7 @@ public void ExposeToCPP()
             //tileset.useLodTransitions = tileset.useLodTransitions;
             //tileset.lodTransitionLength = tileset.lodTransitionLength;
             tileset.generateSmoothNormals = tileset.generateSmoothNormals;
+            tileset.alwaysIncludeTangents = tileset.alwaysIncludeTangents; 
             tileset.ignoreKhrMaterialsUnlit = tileset.ignoreKhrMaterialsUnlit;
             tileset.createPhysicsMeshes = tileset.createPhysicsMeshes;
             tileset.suspendUpdate = tileset.suspendUpdate;

Runtime/Resources/CesiumDefaultTilesetMaterial.mat

@@ -23,13 +23,15 @@ Material:
   m_Name: CesiumDefaultTilesetMaterial
   m_Shader: {fileID: -6465566751694194690, guid: 407c0cff68611ac46a65eec87a5203f5,
     type: 3}
+  m_Parent: {fileID: 0}
+  m_ModifiedSerializedProperties: 0
   m_ValidKeywords:
   - _ALPHATEST_ON
   - _BUILTIN_ALPHATEST_ON
   - _BUILTIN_AlphaClip
+  m_InvalidKeywords:
   - _DISABLE_SSR_TRANSPARENT
   - _DOUBLESIDED_ON
-  m_InvalidKeywords: []
   m_LightmapFlags: 2
   m_EnableInstancingVariants: 0
   m_DoubleSidedGI: 1
@@ -43,6 +45,7 @@ Material:
   - TransparentBackface
   - RayTracingPrepass
   - MOTIONVECTORS
+  m_LockedProperties: 
   m_SavedProperties:
     serializedVersion: 3
     m_TexEnvs:
@@ -101,7 +104,7 @@ Material:
     - _AlphaCutoffEnable: 1
     - _AlphaDstBlend: 0
     - _AlphaSrcBlend: 1
-    - _AlphaToMask: 0
+    - _AlphaToMask: 1
     - _AlphaToMaskInspectorValue: 0
     - _BUILTIN_AlphaClip: 1
     - _BUILTIN_Blend: 0
@@ -116,6 +119,7 @@ Material:
     - _BUILTIN_ZWriteControl: 0
     - _Blend: 0
     - _BlendMode: 0
+    - _BlendModePreserveSpecular: 0
     - _CastShadows: 1
     - _ConservativeDepthOffsetEnable: 0
     - _Cull: 0
@@ -222,4 +226,4 @@ MonoBehaviour:
   m_Script: {fileID: 11500000, guid: d0353a89b1f911e48b9e16bdc9f2e058, type: 3}
   m_Name: 
   m_EditorClassIdentifier: 
-  version: 5
+  version: 7