diff --git a/Extensions/3D/JsExtension.js b/Extensions/3D/JsExtension.js
index c1e15f1524..58c36d9c2a 100644
--- a/Extensions/3D/JsExtension.js
+++ b/Extensions/3D/JsExtension.js
@@ -1901,6 +1901,11 @@ module.exports = {
         .getOrCreate('density')
         .setValue('0.0012')
         .setLabel(_('Density'))
+        .setDescription(
+          _(
+            'Density of the fog. Usual values are between 0.0005 (far away) and 0.005 (very thick fog).'
+          )
+        )
         .setType('number');
     }
     {