Add support for points and lines (#456)

* rename some instances of the word triangles to indices to avoid future invalid assumptions

* simplify and optimize triangle face flipping

* add support for points, lines and line-strip

* if mesh is not triangles, then don't recalculate normals to avoid unnecessary log spam.

Author: aidinabedi

GLTFSerialization/GLTFSerialization/Schema/MeshPrimitive.cs

@@ -98,17 +98,15 @@ public MeshPrimitive(MeshPrimitive meshPrimitive, GLTFRoot gltfRoot) : base(mesh
 			}
 		}
 
-		public static int[] GenerateTriangles(int vertCount)
+		public static int[] GenerateIndices(int vertCount)
 		{
-			var arr = new int[vertCount];
-			for (var i = 0; i < vertCount; i+=3)
+			var indices = new int[vertCount];
+			for (var i = 0; i < vertCount; i++)
 			{
-				arr[i] = i + 2;
-				arr[i + 1] = i + 1;
-				arr[i + 2] = i;
+				indices[i] = i;
 			}
 
-			return arr;
+			return indices;
 		}
 
 		// Taken from: http://answers.unity3d.com/comments/190515/view.html

UnityGLTF/Assets/UnityGLTF/Scripts/Editor/GLTFImporter.cs

@@ -90,7 +90,7 @@ public override void OnImportAsset(AssetImportContext ctx)
                     {
                         mesh.normals = new Vector3[0];
                     }
-                    if (_importNormals == GLTFImporterNormals.Calculate)
+                    if (_importNormals == GLTFImporterNormals.Calculate && mesh.GetTopology(0) == MeshTopology.Triangles)
                     {
                         mesh.RecalculateNormals();
                     }

UnityGLTF/Assets/UnityGLTF/Scripts/Extensions/SchemaExtensions.cs

@@ -439,39 +439,20 @@ public static Vector4[] ConvertVector4CoordinateSpaceAndCopy(Vector4[] array, GL
 			}
 
 			return returnArray;
-		}
-
+		}
+
 		/// <summary>
 		/// Rewinds the indicies into Unity coordinate space from glTF space
 		/// </summary>
 		/// <param name="attributeAccessor">The attribute accessor to modify</param>
-		public static void FlipFaces(ref AttributeAccessor attributeAccessor)
-		{
-			for (int i = 0; i < attributeAccessor.AccessorContent.AsTriangles.Length; i += 3)
-			{
-				uint temp = attributeAccessor.AccessorContent.AsUInts[i];
-				attributeAccessor.AccessorContent.AsUInts[i] = attributeAccessor.AccessorContent.AsUInts[i + 2];
-				attributeAccessor.AccessorContent.AsUInts[i + 2] = temp;
-			}
-		}
-
-		/// <summary>
-		/// Rewinds the indices from glTF space to Unity space
-		/// </summary>
-		/// <param name="triangles">The indices to copy and modify</param>
-		/// <returns>Indices in glTF space that are copied</returns>
-		public static int[] FlipFacesAndCopy(int[] triangles)
+		public static void FlipTriangleFaces(int[] indices)
 		{
-			int[] returnArr = new int[triangles.Length];
-			for (int i = 0; i < triangles.Length; i += 3)
+			for (int i = 0; i < indices.Length; i += 3)
 			{
-				int temp = triangles[i];
-				returnArr[i] = triangles[i + 2];
-				returnArr[i + 1] = triangles[i + 1];
-				returnArr[i + 2] = temp;
+				int temp = indices[i];
+				indices[i] = indices[i + 2];
+				indices[i + 2] = temp;
 			}
-
-			return returnArr;
 		}
 
 		public static Matrix4x4 ToUnityMatrix4x4(this GLTF.Math.Matrix4x4 matrix)

UnityGLTF/Assets/UnityGLTF/Scripts/GLTFSceneExporter.cs

@@ -776,8 +776,12 @@ private MeshPrimitive[] ExportPrimitive(GameObject gameObject, GLTFMesh mesh)
 			{
 				var primitive = new MeshPrimitive();
 
-				var triangles = meshObj.GetTriangles(submesh);
-				primitive.Indices = ExportAccessor(SchemaExtensions.FlipFacesAndCopy(triangles), true);
+				var topology = meshObj.GetTopology(submesh);
+				var indices = meshObj.GetIndices(submesh);
+				if (topology == MeshTopology.Triangles) SchemaExtensions.FlipTriangleFaces(indices);
+
+				primitive.Mode = GetDrawMode(topology);
+				primitive.Indices = ExportAccessor(indices, true);
 
 				primitive.Attributes = new Dictionary<string, AccessorId>();
 				primitive.Attributes.Add(SemanticProperties.POSITION, aPosition);
@@ -1964,6 +1968,18 @@ public SamplerId GetSamplerId(GLTFRoot root, Texture textureObj)
 
 			return null;
 		}
-
+
+		protected static DrawMode GetDrawMode(MeshTopology topology)
+		{
+			switch (topology)
+			{
+				case MeshTopology.Points: return DrawMode.Points;
+				case MeshTopology.Lines: return DrawMode.Lines;
+				case MeshTopology.LineStrip: return DrawMode.LineStrip;
+				case MeshTopology.Triangles: return DrawMode.Triangles;
+			}
+
+			throw new Exception("glTF does not support Unity mesh topology: " + topology);
+		}
 	}
 }

UnityGLTF/Assets/UnityGLTF/Scripts/GLTFSceneImporter.cs

@@ -46,7 +46,8 @@ public class UnityMeshData
 		public Vector2[] Uv3;
 		public Vector2[] Uv4;
 		public Color[] Colors;
-		public int[] Triangles;
+		public MeshTopology Topology;
+		public int[] Indices;
 		public Vector4[] Tangents;
 		public BoneWeight[] BoneWeights;
 	}
@@ -902,11 +903,6 @@ protected void TransformAttributes(ref Dictionary<string, AttributeAccessor> att
 				AttributeAccessor attributeAccessor = attributeAccessors[SemanticProperties.POSITION];
 				SchemaExtensions.ConvertVector3CoordinateSpace(ref attributeAccessor, SchemaExtensions.CoordinateSpaceConversionScale);
 			}
-			if (attributeAccessors.ContainsKey(SemanticProperties.INDICES))
-			{
-				AttributeAccessor attributeAccessor = attributeAccessors[SemanticProperties.INDICES];
-				SchemaExtensions.FlipFaces(ref attributeAccessor);
-			}
 			if (attributeAccessors.ContainsKey(SemanticProperties.NORMAL))
 			{
 				AttributeAccessor attributeAccessor = attributeAccessors[SemanticProperties.NORMAL];
@@ -1708,6 +1704,13 @@ protected UnityMeshData ConvertAccessorsToUnityTypes(MeshConstructionData meshCo
 
 			int vertexCount = (int)primitive.Attributes[SemanticProperties.POSITION].Value.Count;
 
+			var indices = primitive.Indices != null
+					? meshAttributes[SemanticProperties.INDICES].AccessorContent.AsUInts.ToIntArrayRaw()
+					: MeshPrimitive.GenerateIndices(vertexCount);
+
+			var topology = GetTopology(meshConstructionData.Primitive.Mode);
+			if (topology == MeshTopology.Triangles) SchemaExtensions.FlipTriangleFaces(indices);
+
 			return new UnityMeshData
 			{
 				Vertices = primitive.Attributes.ContainsKey(SemanticProperties.POSITION)
@@ -1738,9 +1741,8 @@ protected UnityMeshData ConvertAccessorsToUnityTypes(MeshConstructionData meshCo
 					? meshAttributes[SemanticProperties.Color(0)].AccessorContent.AsColors.ToUnityColorRaw()
 					: null,
 
-				Triangles = primitive.Indices != null
-					? meshAttributes[SemanticProperties.INDICES].AccessorContent.AsUInts.ToIntArrayRaw()
-					: MeshPrimitive.GenerateTriangles(vertexCount),
+				Topology = topology,
+				Indices = indices,
 
 				Tangents = primitive.Attributes.ContainsKey(SemanticProperties.TANGENT)
 					? meshAttributes[SemanticProperties.TANGENT].AccessorContent.AsTangents.ToUnityVector4Raw()
@@ -1857,14 +1859,14 @@ protected async Task ConstructUnityMesh(MeshConstructionData meshConstructionDat
 			await YieldOnTimeoutAndThrowOnLowMemory();
 			mesh.colors = unityMeshData.Colors;
 			await YieldOnTimeoutAndThrowOnLowMemory();
-			mesh.triangles = unityMeshData.Triangles;
+			mesh.SetIndices(unityMeshData.Indices, unityMeshData.Topology, 0);
 			await YieldOnTimeoutAndThrowOnLowMemory();
 			mesh.tangents = unityMeshData.Tangents;
 			await YieldOnTimeoutAndThrowOnLowMemory();
 			mesh.boneWeights = unityMeshData.BoneWeights;
 			await YieldOnTimeoutAndThrowOnLowMemory();
 
-			if (!hasNormals)
+			if (!hasNormals && unityMeshData.Topology == MeshTopology.Triangles)
 			{
 				mesh.RecalculateNormals();
 			}
@@ -2311,6 +2313,18 @@ protected static string AbsoluteFilePath(string gltfPath)
 			return partialPath;
 		}
 
+		protected static MeshTopology GetTopology(DrawMode mode)
+		{
+			switch (mode) {
+				case DrawMode.Points: return MeshTopology.Points;
+				case DrawMode.Lines: return MeshTopology.Lines;
+				case DrawMode.LineStrip: return MeshTopology.LineStrip;
+				case DrawMode.Triangles: return MeshTopology.Triangles;
+			}
+
+			throw new Exception("Unity does not support glTF draw mode: " + mode);
+		}
+
 		/// <summary>
 		/// Cleans up any undisposed streams after loading a scene or a node.
 		/// </summary>