diff --git a/Assets/IsoTools/Docs/CHANGELOG.md b/Assets/IsoTools/Docs/CHANGELOG.md
index 26f2588..71eb141 100644
--- a/Assets/IsoTools/Docs/CHANGELOG.md
+++ b/Assets/IsoTools/Docs/CHANGELOG.md
@@ -1,6 +1,7 @@
 ###### Version 3.1.0
 
 * Fix Unity 5.6 warning
+* Speed up debug gizmos render
 * Disable iso object snapping by children
 
 ###### Version 3.0.2
diff --git a/Assets/IsoTools/Scripts/IsoObject.cs b/Assets/IsoTools/Scripts/IsoObject.cs
index 3535c29..76756bd 100644
--- a/Assets/IsoTools/Scripts/IsoObject.cs
+++ b/Assets/IsoTools/Scripts/IsoObject.cs
@@ -316,14 +316,14 @@ namespace IsoTools {
 		void OnDrawGizmos() {
 			var iso_world = isoWorld;
 			if ( iso_world ) {
-				if ( iso_world.isShowIsoBounds ) {
+				if ( iso_world.isShowIsoBounds && iso_world.Internal_IsVisible(this) ) {
 					IsoUtils.DrawIsoCube(
 						iso_world,
 						position + size * 0.5f,
 						size,
 						Color.red);
 				}
-				if ( iso_world.isShowScreenBounds ) {
+				if ( iso_world.isShowScreenBounds && iso_world.Internal_IsVisible(this) ) {
 					IsoUtils.DrawRect(
 						Internal.QTBounds,
 						Color.green);
@@ -333,7 +333,7 @@ namespace IsoTools {
 
 		void OnDrawGizmosSelected() {
 			var iso_world = isoWorld;
-			if ( iso_world && iso_world.isShowDepends ) {
+			if ( iso_world && iso_world.isShowDepends && iso_world.Internal_IsVisible(this) ) {
 				for ( int i = 0, e = Internal.SelfDepends.Count; i < e; ++i ) {
 					IsoUtils.DrawLine(
 						Internal.QTBounds.center,
diff --git a/Assets/IsoTools/Scripts/IsoWorld.cs b/Assets/IsoTools/Scripts/IsoWorld.cs
index 0239fea..f4d7035 100644
--- a/Assets/IsoTools/Scripts/IsoWorld.cs
+++ b/Assets/IsoTools/Scripts/IsoWorld.cs
@@ -443,6 +443,10 @@ namespace IsoTools {
 			}
 		}
 
+		public bool Internal_IsVisible(IsoObject iso_object) {
+			return _screenSolver.curVisibles.Contains(iso_object);
+		}
+
 		// ---------------------------------------------------------------------
 		//
 		// Private