diff --git a/src/shaders/world.frag b/src/shaders/world.frag
index fae319b..a2a19a4 100644
--- a/src/shaders/world.frag
+++ b/src/shaders/world.frag
@@ -22,5 +22,11 @@ void main()	{
         materialId = float(MAT_AIR);
     }
 
+    // ant deposited material at this cell (only into air cells)
+    int depositMatId = int(round(discreteAnts.w * 255.));
+    if (depositMatId > 0 && int(materialId) == MAT_AIR) {
+        materialId = float(depositMatId);
+    }
+
     FragColor = vec4(materialId, scentToHome, scentToFood, repellent);
 }