Remove mesh from preview render data and check for preview mesh in preview manager

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Inspector/GraphInspectorView.cs

 
         void OnPreviewMeshChanged(ChangeEvent<UnityEngine.Object> changeEvent)
         {
-            if (changeEvent.newValue == null)
-            {
-                m_PreviewRenderHandle.mesh = null;
-            }
-
-
-            if (changedMesh)
-            {
-                m_PreviewRenderHandle.mesh = changedMesh;
-            }
 
             masterNode.onModified(masterNode, ModificationScope.Node);
 

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/PreviewManager.cs

             if (masterRenderData.shaderData != null && m_DirtyPreviews.Contains(masterRenderData.shaderData.node.guid))
                 m_RenderList3D.Add(masterRenderData);
 
+            m_RenderList3D.Sort((data1, data2) => data1.shaderData.shader.GetInstanceID().CompareTo(data2.shaderData.shader.GetInstanceID()));
+            m_RenderList2D.Sort((data1, data2) => data1.shaderData.shader.GetInstanceID().CompareTo(data2.shaderData.shader.GetInstanceID()));
+
+
             m_SceneResources.light0.enabled = true;
             m_SceneResources.light0.intensity = 1.0f;
             m_SceneResources.light0.transform.rotation = Quaternion.Euler(50f, 50f, 0);
             m_SceneResources.camera.transform.rotation = Quaternion.identity;
             m_SceneResources.camera.orthographicSize = 1;
             m_SceneResources.camera.orthographic = true;
-            m_RenderList2D.Sort((data1, data2) => data1.shaderData.shader.GetInstanceID().CompareTo(data2.shaderData.shader.GetInstanceID()));
+
             foreach (var renderData in m_RenderList2D)
             {
                 int outputId;
             m_SceneResources.camera.transform.position = -Vector3.forward * 5;
             m_SceneResources.camera.transform.rotation = Quaternion.identity;
             m_SceneResources.camera.orthographic = false;
-            m_RenderList3D.Sort((data1, data2) => data1.shaderData.shader.GetInstanceID().CompareTo(data2.shaderData.shader.GetInstanceID()));
+
             foreach (var renderData in m_RenderList3D)
             {
                 int outputId;
                 RenderTexture.active = renderData.renderTexture;
                 GL.Clear(true, true, Color.black);
                 Graphics.Blit(Texture2D.whiteTexture, renderData.renderTexture, m_SceneResources.checkerboardMaterial);
-                var mesh = renderData.mesh ?? m_SceneResources.sphere;
+                var mesh = (renderData == masterRenderData && m_Graph.previewMesh) ? m_Graph.previewMesh :  m_SceneResources.sphere;
                 Graphics.DrawMesh(mesh, Matrix4x4.TRS(-mesh.bounds.center, Quaternion.identity, Vector3.one), m_PreviewMaterial, 1, m_SceneResources.camera, 0, m_PreviewPropertyBlock, ShadowCastingMode.Off, false, null, false);
                 var previousUseSRP = Unsupported.useScriptableRenderPipeline;
                 Unsupported.useScriptableRenderPipeline = renderData.shaderData.node is IMasterNode;
     public class PreviewRenderData
     {
         public PreviewShaderData shaderData { get; set; }
-        public Mesh mesh { get; set; }
         public RenderTexture renderTexture { get; set; }
         public Texture texture { get; set; }
         public OnPreviewChanged onPreviewChanged;