[Rendering] Adds support for DrawAuto and DrawIndirect to MeshDraw

sources/engine/Stride.Graphics/IndirectDrawingArgs.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Stride contributors (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 System;
+using Stride.Core.Serialization;
+using Stride.Core.Serialization.Serializers;
+
+namespace Stride.Graphics
+{
+    public class IndirectDrawingArgs
+    {
+        /// <summary>
+        /// Creates an instance of <see cref="IndirectDrawingArgs"/> for DrawAuto with a stream-out vertex buffer.
+        /// </summary>
+        public IndirectDrawingArgs()
+        {
+            DrawAuto = true;
+        }
+
+        /// <summary>
+        /// Creates an instance of <see cref="IndirectDrawingArgs"/> for DrawIndirect with a buffer containing the draw arguments.
+        /// </summary>
+        public IndirectDrawingArgs(Buffer argumentBuffer, int alignedByteOffset = 0)
+        {
+            if (argumentBuffer == null) throw new ArgumentNullException("argmentBuffer");
+            ArgumentBuffer = argumentBuffer;
+            AlignedByteOffset = alignedByteOffset;
+        }
+
+        public readonly bool DrawAuto;
+        public readonly Buffer ArgumentBuffer;
+        public readonly int AlignedByteOffset;
+    }
+}

sources/engine/Stride.Rendering/Rendering/Materials/MaterialRenderFeature.cs

@@ -136,11 +136,12 @@ public override void PrepareEffectPermutations(RenderDrawContext context)
                         var oldMeshDraw = renderMesh.ActiveMeshDraw;
                         tessellationMeshDraw = new MeshDraw
                         {
-                            VertexBuffers = oldMeshDraw.VertexBuffers,
-                            IndexBuffer = oldMeshDraw.IndexBuffer,
+                            PrimitiveType = tessellationState.Method.GetPrimitiveType(),
                             DrawCount = oldMeshDraw.DrawCount,
                             StartLocation = oldMeshDraw.StartLocation,
-                            PrimitiveType = tessellationState.Method.GetPrimitiveType(),
+                            VertexBuffers = oldMeshDraw.VertexBuffers,
+                            IndexBuffer = oldMeshDraw.IndexBuffer,
+                            IndirectDrawing = oldMeshDraw.IndirectDrawing,
                         };
 
                         // adapt the primitive type and index buffer to the tessellation used

sources/engine/Stride.Rendering/Rendering/MeshDraw.cs

@@ -19,5 +19,8 @@ public class MeshDraw
         public VertexBufferBinding[] VertexBuffers;
 
         public IndexBufferBinding IndexBuffer;
+
+        [DataMemberIgnore]
+        public IndirectDrawingArgs IndirectDrawing;
     }
 }

sources/engine/Stride.Rendering/Rendering/MeshRenderFeature.cs

@@ -215,19 +215,47 @@ public override void Draw(RenderDrawContext context, RenderView renderView, Rend
                 commandList.SetDescriptorSets(0, descriptorSetsLocal);
 
                 // Draw
-                if (drawData.IndexBuffer == null)
+                if (drawData.IndexBuffer is null)
                 {
-                    if (renderMesh.InstanceCount > 0)
-                        commandList.DrawInstanced(drawData.DrawCount, renderMesh.InstanceCount, drawData.StartLocation);
-                    else
-                        commandList.Draw(drawData.DrawCount, drawData.StartLocation);
+                    if (drawData.IndirectDrawing is null) //direct drawing
+                    {
+                        if (renderMesh.InstanceCount > 0)
+                            commandList.DrawInstanced(drawData.DrawCount, renderMesh.InstanceCount, drawData.StartLocation);
+                        else
+                            commandList.Draw(drawData.DrawCount, drawData.StartLocation);
+                    }
+                    else // indirect drawing
+                    {
+                        if (drawData.IndirectDrawing.DrawAuto)
+                        {
+                            commandList.DrawAuto();
+                        }
+                        else
+                        {
+                            commandList.DrawInstanced(drawData.IndirectDrawing.ArgumentBuffer, drawData.IndirectDrawing.AlignedByteOffset);
+                        }
+                    }
                 }
                 else
                 {
-                    if (renderMesh.InstanceCount > 0)
-                        commandList.DrawIndexedInstanced(drawData.DrawCount, renderMesh.InstanceCount, drawData.StartLocation);
-                    else
-                        commandList.DrawIndexed(drawData.DrawCount, drawData.StartLocation);
+                    if (drawData.IndirectDrawing is null) //direct drawing
+                    {
+                        if (renderMesh.InstanceCount > 0)
+                            commandList.DrawIndexedInstanced(drawData.DrawCount, renderMesh.InstanceCount, drawData.StartLocation);
+                        else
+                            commandList.DrawIndexed(drawData.DrawCount, drawData.StartLocation);
+                    }
+                    else // indirect drawing
+                    {
+                        if (drawData.IndirectDrawing.DrawAuto)
+                        {
+                            // throw exception? DrawAuto should not have an index buffer, as it always comes from the stream out stage
+                        }
+                        else
+                        { 
+                            commandList.DrawIndexedInstanced(drawData.IndirectDrawing.ArgumentBuffer, drawData.IndirectDrawing.AlignedByteOffset);
+                        }
+                    }
                 }
             }
         }