add gpu instancing metadata

README.md

@@ -202,7 +202,11 @@ There is an experimental option to create 3D Tiles 1.1 using GPU instancing: --u
 
 This option is currently in development. 
 
-The following features should work: Positioning, Rotation (roll, pitch, yaw) and Scaling of instances.
+The following features should work: 
+
+- Attribute information from tags using EXT_structural_metadata, EXT_mesh_gpu_instancing and EXT_instance_features. 
+
+- Positioning, Rotation (roll, pitch, yaw) and Scaling of instances.
 
 To use this option, the input table should contain columns 'roll', 'pitch' and 'yaw' (column 'rotation' is not used).
 
@@ -217,9 +221,9 @@ alter table instances drop column rotation
 
 The columns should be filled with radian angles (0 - 2PI).
 
-The following features are not yet supported when using use_gpu_instancing: 
+Known limits:
 
-- batch information (EXT_Mesh_Features/EXT_Structural_Metadata)
+- When using GPU instancing, the column type 'string' is used (so no support for other types yet). 
 
 - composite tiles (formerly known as cmpt). When there are multiple models in the input table only the first one is used.
 
@@ -253,6 +257,8 @@ To Visualize in CesiumJS, add references to:
 
 ## History
 
+2023-03-28: release 2.7.0: add support for EXT_structural_metadata
+
 2023-11-08: release 2.6.0: Add support for GPU instancing (experimental), removed option -r RTC_CENTER 
 
 2023-10-18: release 2.5.0: Improved root bounding volume calculation, improved batch table handling

src/Program.cs

@@ -3,6 +3,7 @@
 using i3dm.export.Cesium;
 using i3dm.export.extensions;
 using Npgsql;
+using SharpGLTF.Schema2;
 using ShellProgressBar;
 using subtree;
 using System;
@@ -97,6 +98,7 @@ static void Main(string[] args)
             if ((bool)o.UseGpuInstancing)
             {
                 translate = new Vector3((float)center_wgs84.X, (float)center_wgs84.Y, (float)center_wgs84.Z);
+                Tiles3DExtensions.RegisterExtensions();
             }
 
             var options = new ProgressBarOptions

src/TileHandler.cs

@@ -1,18 +1,16 @@
 using Cmpt.Tile;
-using i3dm.export.Cesium;
 using I3dm.Tile;
 using Newtonsoft.Json.Linq;
-using SharpGLTF.Geometry.VertexTypes;
-using SharpGLTF.Geometry;
 using SharpGLTF.Scenes;
 using SharpGLTF.Schema2;
 using SharpGLTF.Transforms;
-using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Numerics;
 using Wkx;
+using System.Text.Json.Nodes;
+using SharpGLTF.Schema2.Tiles3D;
 
 namespace i3dm.export;
 
@@ -46,7 +44,12 @@ public static byte[] GetTile(List<Instance> instances, Format format, Vector3 tr
 
             if (useGpuInstancing)
             {
-                var bytesGlb = GetGpuGlb(model, modelInstances, translate, UseScaleNonUniform);
+                foreach (var instance in instances)
+                {
+                    tags.Add(instance.Tags);
+                }
+
+                var bytesGlb = GetGpuGlb(model, modelInstances, translate, UseScaleNonUniform, tags);
                 tiles.Add(bytesGlb);
             }
             else
@@ -94,13 +97,15 @@ private static Vector3 GetPosition(Point p, Vector3 translate)
         return vec;
     }
 
-    private static byte[] GetGpuGlb(object model, List<Instance> positions, Vector3 translate, bool UseScaleNonUniform)
+    private static byte[] GetGpuGlb(object model, List<Instance> positions, Vector3 translate, bool UseScaleNonUniform, List<JArray> tags)
     {
         var modelRoot = ModelRoot.Load((string)model);
         var meshBuilder = modelRoot.LogicalMeshes.First().ToMeshBuilder();
 
         var sceneBuilder = new SceneBuilder();
 
+        var pointId = 0;
+
         foreach (var p in positions)
         {
             var point = (Point)p.Position;
@@ -124,12 +129,50 @@ private static byte[] GetGpuGlb(object model, List<Instance> positions, Vector3
                 scale,
                 quaternion,
                 translation);
-            sceneBuilder.AddRigidMesh(meshBuilder, transformation);
+            var json = "{\"_FEATURE_ID_0\":" + pointId + "}";
+            sceneBuilder.AddRigidMesh(meshBuilder, transformation).WithExtras(JsonNode.Parse(json));
+            pointId++;
         }
 
         var settings = SceneBuilderSchema2Settings.WithGpuInstancing;
         settings.GpuMeshInstancingMinCount = 0;
         var gltf = sceneBuilder.ToGltf2(settings);
+
+        var rootMetadata = gltf.UseStructuralMetadata();
+        var schema = rootMetadata.UseEmbeddedSchema("schema");
+        var schemaClass = schema.UseClassMetadata("propertyTable");
+
+        if(tags.Count > 0)
+        {
+            var propertyTable = schemaClass.AddPropertyTable(positions.Count);
+
+            if (tags[0] != null)
+            {
+                var properties = TinyJson.GetProperties(tags[0]);
+                foreach(var property in properties)
+                {
+                    var values = TinyJson.GetValues(tags, property);
+
+                    var nameProperty = schemaClass
+                    .UseProperty(property)
+                    .WithStringType();
+
+                    // todo: use other types than string
+                    var strings = values.Select(s => s.ToString()).ToArray();
+
+                    propertyTable
+                        .UseProperty(nameProperty)
+                        .SetValues(strings);
+                }
+            }
+
+
+            var featureId0 = new FeatureIDBuilder(positions.Count, 0, propertyTable);
+            gltf.LogicalNodes[0].AddInstanceFeatureIds(featureId0);
+
+        }
+
+
         var bytes = gltf.WriteGLB().Array;
         return bytes;
     }

src/TinyJson.cs

@@ -42,7 +42,7 @@ public static string ToJson(List<JArray> tags, List<string> properties)
         return resres;
     }
 
-    private static List<object> GetValues(List<JArray> tags, string prop)
+    public static List<object> GetValues(List<JArray> tags, string prop)
     {
         var res = new List<Object>();
         foreach (var tag in tags)

tests/TileHandlerTests.cs

@@ -2,6 +2,8 @@
 using I3dm.Tile;
 using Newtonsoft.Json.Linq;
 using NUnit.Framework;
+using SharpGLTF.Schema2;
+using SharpGLTF.Schema2.Tiles3D;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
@@ -14,29 +16,38 @@ public class TileHandlerTests
     [Test]
     public void GetGpuTileTest()
     {
+        Tiles3DExtensions.RegisterExtensions();
+
         // arrange
         var instances = new List<Instance>();
         var instance = new Instance();
         instance.Position = new Wkx.Point(1, 2, 0);
         instance.Scale = 1;
         instance.Model = "Box.glb";
+        instance.Tags = JArray.Parse("[{'id':123},{'name': 'test'}]");
         instances.Add(instance);
 
         // act
-        var tile = TileHandler.GetTile(instances, Format.Cesium, Vector3.Zero,useGpuInstancing:true);
+        var tile = TileHandler.GetTile(instances, Format.Cesium, Vector3.Zero, useGpuInstancing: true);
 
         var fileName = Path.Combine(TestContext.CurrentContext.WorkDirectory, "ams_building_multiple_colors.glb");
         File.WriteAllBytes(fileName, tile);
 
-        var model = SharpGLTF.Schema2.ModelRoot.Load(fileName);
-
+        var model = ModelRoot.Load(fileName);
+        var extInstanceFeaturesExtension = model.LogicalNodes[0].GetExtension<MeshExtInstanceFeatures>();
+
+        var extStructuralMetadataExtension = model.GetExtension<EXTStructuralMetadataRoot>();
+        Assert.That(extStructuralMetadataExtension != null);
+
+        var fid0 = extInstanceFeaturesExtension.FeatureIds[0];
+        Assert.That(fid0.FeatureCount == 1);
+
+
         // assert
         // todo: can we read the instance positions from the glb?
         Assert.That(tile.Length > 0);
     }
 
-
-
     [Test]
     public void GetTileTest()
     {
@@ -164,7 +175,7 @@ public void GetTileWithRtcCenterTest()
         instances.Add(instance1);
 
         // act
-        var tile = TileHandler.GetTile(instances, Format.Mapbox,translate: new Vector3(5, 5, 0));
+        var tile = TileHandler.GetTile(instances, Format.Mapbox, translate: new Vector3(5, 5, 0));
         var cmpt = CmptReader.Read(new MemoryStream(tile));
         var i3dm = I3dmReader.Read(new MemoryStream(cmpt.Tiles.First()));