New extension classes to create a Model at the run-time

FNA.Core.csproj

@@ -188,6 +188,7 @@
 		<Compile Include="src\Graphics\Model.cs" />
 		<Compile Include="src\Graphics\ModelBone.cs" />
 		<Compile Include="src\Graphics\ModelBoneCollection.cs" />
+		<Compile Include="src\Graphics\ModelBuilderEXT.cs" />
 		<Compile Include="src\Graphics\ModelEffectCollection.cs" />
 		<Compile Include="src\Graphics\ModelMesh.cs" />
 		<Compile Include="src\Graphics\ModelMeshCollection.cs" />

FNA.NetFramework.csproj

@@ -189,6 +189,7 @@
 		<Compile Include="src\Graphics\Model.cs" />
 		<Compile Include="src\Graphics\ModelBone.cs" />
 		<Compile Include="src\Graphics\ModelBoneCollection.cs" />
+		<Compile Include="src\Graphics\ModelBuilderEXT.cs" />
 		<Compile Include="src\Graphics\ModelEffectCollection.cs" />
 		<Compile Include="src\Graphics\ModelMesh.cs" />
 		<Compile Include="src\Graphics\ModelMeshCollection.cs" />

FNA.NetStandard.csproj

@@ -188,6 +188,7 @@
 		<Compile Include="src\Graphics\Model.cs" />
 		<Compile Include="src\Graphics\ModelBone.cs" />
 		<Compile Include="src\Graphics\ModelBoneCollection.cs" />
+		<Compile Include="src\Graphics\ModelBuilderEXT.cs" />
 		<Compile Include="src\Graphics\ModelEffectCollection.cs" />
 		<Compile Include="src\Graphics\ModelMesh.cs" />
 		<Compile Include="src\Graphics\ModelMeshCollection.cs" />

FNA.csproj

@@ -259,6 +259,7 @@
     <Compile Include="src\Graphics\Model.cs" />
     <Compile Include="src\Graphics\ModelBone.cs" />
     <Compile Include="src\Graphics\ModelBoneCollection.cs" />
+    <Compile Include="src\Graphics\ModelBuilderEXT.cs" />
     <Compile Include="src\Graphics\ModelEffectCollection.cs" />
     <Compile Include="src\Graphics\ModelMesh.cs" />
     <Compile Include="src\Graphics\ModelMeshCollection.cs" />

src/Graphics/ModelBuilderEXT.cs

@@ -0,0 +1,227 @@
+using System;
+using System.Collections.Generic;
+using System.Security.Cryptography;
+
+namespace Microsoft.Xna.Framework.Graphics
+{
+	/// <summary>
+	/// Model mesh descriptor
+	/// </summary>
+	public class ModelMeshDescEXT
+	{
+		/// <summary>
+		/// Name of the model mesh
+		/// </summary>
+		public string Name { get; set; }
+
+		/// <summary>
+		/// Bounding Sphere of the model mesh
+		/// </summary>
+		public BoundingSphere BoundingSphere { get; set; }
+
+		/// <summary>
+		/// Parts of the model mesh
+		/// </summary>
+		public readonly List<ModelMeshPart> Parts = new List<ModelMeshPart>();
+
+		internal int Index { get; set; }
+
+		/// <summary>
+		/// Adds a mesh part to the model mesh
+		/// </summary>
+		/// <param name="indexBuffer">The index buffer for this mesh part</param>
+		/// <param name="startIndex">The location in the index array at which to start reading vertices</param>
+		/// <param name="vertexBuffer">The vertex buffer for this mesh part</param>
+		/// <param name="vertexOffset">The offset (in vertices) from the top of vertex buffer</param>
+		/// <param name="numVertices">The number of vertices used during a draw call</param>
+		/// <param name="primitiveCount">The number of primitives to render</param>
+		/// <exception cref="ArgumentNullException"></exception>
+		/// <exception cref="ArgumentOutOfRangeException"></exception>
+		public void AddModelMeshPart(IndexBuffer indexBuffer, int startIndex,
+			VertexBuffer vertexBuffer, int vertexOffset, int numVertices,
+			int primitiveCount)
+		{
+			if (indexBuffer == null)
+			{
+				throw new ArgumentNullException(nameof(indexBuffer));
+			}
+
+			if (startIndex < 0 || startIndex >= indexBuffer.IndexCount)
+			{
+				throw new ArgumentOutOfRangeException(nameof(startIndex));
+			}
+
+			if (vertexBuffer == null)
+			{
+				throw new ArgumentNullException(nameof(vertexBuffer));
+			}
+
+			if (vertexOffset < 0 || vertexOffset >= vertexBuffer.VertexCount)
+			{
+				throw new ArgumentOutOfRangeException(nameof(vertexOffset));
+			}
+
+			if (numVertices <= 0 || numVertices > vertexBuffer.VertexCount)
+			{
+				throw new ArgumentOutOfRangeException(nameof(numVertices));
+			}
+
+			if (primitiveCount <= 0)
+			{
+				throw new ArgumentOutOfRangeException(nameof(primitiveCount));
+			}
+
+			var part = new ModelMeshPart()
+			{
+				IndexBuffer = indexBuffer,
+				StartIndex = startIndex,
+				VertexBuffer = vertexBuffer,
+				VertexOffset = vertexOffset,
+				NumVertices = numVertices,
+				PrimitiveCount = primitiveCount
+			};
+
+			Parts.Add(part);
+		}
+
+		/// <summary>
+		/// Creates the model mesh
+		/// </summary>
+		/// <param name="device">Graphics Device</param>
+		/// <returns></returns>
+		public ModelMesh Create(GraphicsDevice device)
+		{
+			var modelMesh = new ModelMesh(device, Parts)
+			{
+				Name = Name,
+				BoundingSphere = BoundingSphere,
+			};
+
+			return modelMesh;
+		}
+	}
+
+	/// <summary>
+	/// Model bone descriptor
+	/// </summary>
+	public class ModelBoneDescEXT
+	{
+		/// <summary>
+		/// Name of the model bone
+		/// </summary>
+		public string Name { get; set; }
+
+		/// <summary>
+		/// Transform of the model bone
+		/// </summary>
+		public Matrix Transform { get; set; }
+
+		/// <summary>
+		/// Meshes of the model bone
+		/// </summary>
+		public readonly List<ModelMeshDescEXT> Meshes = new List<ModelMeshDescEXT>();
+
+		/// <summary>
+		/// Children of the model bone
+		/// </summary>
+		public readonly List<ModelBoneDescEXT> Children = new List<ModelBoneDescEXT>();
+
+		internal int Index { get; set; }
+	}
+
+	/// <summary>
+	/// Grants ability to create a Model at the run-time
+	/// </summary>
+	public static class ModelBuilderEXT
+	{
+		/// <summary>
+		/// Creates the model
+		/// </summary>
+		/// <param name="device">Graphics Device</param>
+		/// <param name="meshes">Meshes of the model</param>
+		/// <param name="bones">Bones of the model</param>
+		/// <param name="root">Root bone of the model</param>
+		/// <returns></returns>
+		/// <exception cref="ArgumentOutOfRangeException"></exception>
+		public static Model Create(GraphicsDevice device, List<ModelMeshDescEXT> meshes, List<ModelBoneDescEXT> bones, ModelBoneDescEXT root)
+		{
+			if (meshes == null)
+			{
+				throw new ArgumentNullException(nameof(meshes));
+			}
+
+			if (bones == null)
+			{
+				throw new ArgumentNullException(nameof(bones));
+			}
+
+			if (root == null)
+			{
+				throw new ArgumentNullException(nameof(root));
+			}
+
+			// Assign indexes
+			for (var i = 0; i < meshes.Count; ++i)
+			{
+				meshes[i].Index = i;
+			}
+
+			for (var i = 0; i < bones.Count; ++i)
+			{
+				bones[i].Index = i;
+			}
+
+			// Create meshes
+			var modelMeshes = new List<ModelMesh>();
+			foreach (var desc in meshes)
+			{
+				var modelMesh = desc.Create(device);
+				modelMeshes.Add(modelMesh);
+			}
+
+			// Create bones
+			var modelBones = new List<ModelBone>();
+			for (var i = 0; i < bones.Count; ++i)
+			{
+				var desc = bones[i];
+				var bone = new ModelBone
+				{
+					Index = i,
+					Name = desc.Name,
+					Transform = desc.Transform
+				};
+
+				foreach (var mesh in desc.Meshes)
+				{
+					var modelMesh = modelMeshes[mesh.Index];
+					modelMesh.ParentBone = bone;
+					bone.AddMesh(modelMesh);
+				}
+
+				modelBones.Add(bone);
+			}
+
+			// Assign children
+			for (var i = 0; i < bones.Count; ++i)
+			{
+				var desc = bones[i];
+				var bone = modelBones[i];
+
+				foreach (var child in desc.Children)
+				{
+					var childBone = modelBones[child.Index];
+					childBone.Parent = bone;
+					bone.AddChild(childBone);
+				}
+			}
+
+			// Create the model
+			var model = new Model(device, modelBones, modelMeshes)
+			{
+				Root = modelBones[root.Index]
+			};
+
+			return model;
+		}
+	}
+}