add node shadow

- rectangular shadow (can be disabled...)
- ... for example for nodes with more complex shapes like reroute

Source/Editor/Surface/Archetypes/Tools.cs

@@ -1059,6 +1059,7 @@ namespace FlaxEditor.Surface.Archetypes
         internal class RerouteNode : SurfaceNode, IConnectionInstigator
         {
             internal static readonly Float2 DefaultSize = new Float2(FlaxEditor.Surface.Constants.BoxRowHeight);
+            internal override bool DrawBasicShadow => false;
             private Rectangle _localBounds;
             private InputBox _input;
             private OutputBox _output;
@@ -1187,6 +1188,11 @@ namespace FlaxEditor.Surface.Archetypes
                     icon = type.IsVoid ? style.Icons.ArrowClose : style.Icons.BoxClose;
                 else
                     icon = type.IsVoid ? style.Icons.ArrowOpen : style.Icons.BoxOpen;
+
+                // Shadow
+                var shadowRect = _localBounds.MakeOffsetted(ShadowOffset);
+                Render2D.DrawSprite(icon, shadowRect, Color.Black.AlphaMultiplied(0.125f));
+
                 Render2D.DrawSprite(icon, _localBounds, connectionColor);
 
                 base.Draw();

Source/Editor/Surface/SurfaceNode.cs

@@ -40,6 +40,13 @@ namespace FlaxEditor.Surface
     [HideInEditor]
     public class SurfaceNode : SurfaceControl
     {
+        internal const float ShadowOffset = 2.25f;
+
+        /// <summary>
+        /// If true, draws a basic rectangle shadow behind the node. Disable to hide shadow or if the node is drawing a custom shadow.
+        /// </summary>
+        internal virtual bool DrawBasicShadow => true;
+
         /// <summary>
         /// The box to draw a highlight around. Drawing will be skipped if null.
         /// </summary>
@@ -1047,8 +1054,16 @@ namespace FlaxEditor.Surface
         {
             var style = Style.Current;
 
-            // Background
             var backgroundRect = new Rectangle(Float2.Zero, Size);
+
+            // Shadow
+            if (DrawBasicShadow)
+            {
+                var shadowRect = backgroundRect.MakeOffsetted(ShadowOffset);
+                Render2D.FillRectangle(shadowRect, Color.Black.AlphaMultiplied(0.125f));
+            }
+
+            // Background
             Render2D.FillRectangle(backgroundRect, BackgroundColor);
 
             // Breakpoint hit
@@ -1085,6 +1100,7 @@ namespace FlaxEditor.Surface
                 var colorTop = Color.Orange;
                 var colorBottom = Color.OrangeRed;
                 Render2D.DrawRectangle(backgroundRect, colorTop, colorTop, colorBottom, colorBottom);
+                Render2D.DrawRectangle(backgroundRect, colorTop, colorTop, colorBottom, colorBottom, 2.5f);
             }
 
             // Breakpoint dot

Source/Engine/Core/Math/Rectangle.cs

@@ -253,6 +253,16 @@ namespace FlaxEngine
             return new Rectangle(Location + new Float2(x, y), Size);
         }
 
+        /// <summary>
+        /// Make offseted rectangle
+        /// </summary>
+        /// <param name="offset">Offset (will be applied to X- and Y- axis).</param>
+        /// <returns>Offseted rectangle.</returns>
+        public Rectangle MakeOffsetted(float offset)
+        {
+            return new Rectangle(Location + new Float2(offset, offset), Size);
+        }
+
         /// <summary>
         /// Make offseted rectangle
         /// </summary>