feat: ModelComponent bounds gizmos (#2294)

sources/editor/Stride.Assets.Presentation/AssetEditors/Gizmos/ModelGizmo.cs

@@ -0,0 +1,121 @@
+// Copyright (c) .NET Foundation and Contributors (https://dotnetfoundation.org/ & https://stride3d.net) and Silicon Studio Corp. (https://www.siliconstudio.co.jp)
+// Distributed under the MIT license. See the LICENSE.md file in the project root for more information.
+using Stride.Core.Mathematics;
+using Stride.Engine;
+using Stride.Graphics;
+using Stride.Rendering;
+using Buffer = Stride.Graphics.Buffer;
+
+namespace Stride.Assets.Presentation.AssetEditors.Gizmos
+{
+    /// <summary>
+    /// A gizmo to display the bounding boxes for meshes inside the editor as a gizmo. 
+    /// this gizmo uses model component bounding box for data <see cref="ModelComponent.BoundingBox">
+    /// </summary>
+    [GizmoComponent(typeof(ModelComponent), false)]
+    public class ModelGizmo : EntityGizmo<ModelComponent>
+    {
+        private BoxMesh box;
+        private Material material;
+        private Entity debugEntity;
+
+        public ModelGizmo(EntityComponent component) : base(component)
+        {
+        }
+
+        protected override Entity Create()
+        {
+            if (debugEntity != null)
+                return debugEntity;
+
+            material = GizmoEmissiveColorMaterial.Create(GraphicsDevice, Color.DarkMagenta);
+
+            box = new BoxMesh(GraphicsDevice);
+            box.Build();
+
+            debugEntity = new Entity($"Model bounding box volume of {Component.Entity.Name}")
+            {
+                new ModelComponent
+                {
+                    Model = new Model
+                    {
+                        material,
+                        new Mesh { Draw = box.MeshDraw },
+                    },
+                    RenderGroup = RenderGroup,
+                }
+            };
+            return debugEntity;
+        }
+
+        public override void Update()
+        {
+            if (ContentEntity == null || GizmoRootEntity == null)
+                return;
+
+            // Translation and Scale but no rotation on bounding boxes
+            GizmoRootEntity.Transform.Position = Component.BoundingBox.Center;
+            GizmoRootEntity.Transform.Scale = Component.BoundingBox.Extent;
+            GizmoRootEntity.Transform.UpdateWorldMatrix();
+        }
+
+        class BoxMesh
+        {
+            public MeshDraw MeshDraw;
+
+            private Buffer vertexBuffer;
+
+            private readonly GraphicsDevice graphicsDevice;
+
+            public BoxMesh(GraphicsDevice graphicsDevice)
+            {
+                this.graphicsDevice = graphicsDevice;
+            }
+
+            public void Build()
+            {
+                var indices = new int[12 * 2];
+                var vertices = new VertexPositionNormalTexture[8];
+
+                vertices[0] = new VertexPositionNormalTexture(new Vector3(-1, 1, -1), Vector3.UnitY, Vector2.Zero);
+                vertices[1] = new VertexPositionNormalTexture(new Vector3(-1, 1, 1), Vector3.UnitY, Vector2.Zero);
+                vertices[2] = new VertexPositionNormalTexture(new Vector3(1, 1, 1), Vector3.UnitY, Vector2.Zero);
+                vertices[3] = new VertexPositionNormalTexture(new Vector3(1, 1, -1), Vector3.UnitY, Vector2.Zero);
+
+                int indexOffset = 0;
+                // Top sides
+                for (int i = 0; i < 4; i++)
+                {
+                    indices[indexOffset++] = i;
+                    indices[indexOffset++] = (i+1)%4;
+                }
+
+                // Duplicate vertices and indices to bottom part
+                for (int i = 0; i < 4; i++)
+                {
+                    vertices[i + 4] = vertices[i];
+                    vertices[i + 4].Position.Y = -vertices[i + 4].Position.Y;
+
+                    indices[indexOffset++] = indices[i * 2] + 4;
+                    indices[indexOffset++] = indices[i * 2 + 1] + 4;
+                }
+
+                // Sides
+                for (int i = 0; i < 4; i++)
+                {
+                    indices[indexOffset++] = i;
+                    indices[indexOffset++] = i + 4;
+                }
+
+                vertexBuffer = Buffer.Vertex.New(graphicsDevice, vertices);
+                MeshDraw = new MeshDraw
+                {
+                    PrimitiveType = PrimitiveType.LineList,
+                    DrawCount = indices.Length,
+                    IndexBuffer = new IndexBufferBinding(Buffer.Index.New(graphicsDevice, indices), true, indices.Length),
+                    VertexBuffers = new[] { new VertexBufferBinding(vertexBuffer, VertexPositionNormalTexture.Layout, vertexBuffer.ElementCount) },
+                };
+            }
+        }
+    }
+}