diff --git a/demo/gdml/src/jvmMain/kotlin/hep/dataforge/vis/spatial/gdml/demo/GDMLDemoApp.kt b/demo/gdml/src/jvmMain/kotlin/hep/dataforge/vis/spatial/gdml/demo/GDMLDemoApp.kt
index b4a75c37..23ac0290 100644
--- a/demo/gdml/src/jvmMain/kotlin/hep/dataforge/vis/spatial/gdml/demo/GDMLDemoApp.kt
+++ b/demo/gdml/src/jvmMain/kotlin/hep/dataforge/vis/spatial/gdml/demo/GDMLDemoApp.kt
@@ -4,15 +4,13 @@ import hep.dataforge.context.Global
 import hep.dataforge.vis.fx.editor.VisualObjectEditorFragment
 import hep.dataforge.vis.fx.editor.VisualObjectTreeFragment
 import hep.dataforge.vis.spatial.Material3D
+import hep.dataforge.vis.spatial.Visual3DPlugin
+import hep.dataforge.vis.spatial.VisualGroup3D
 import hep.dataforge.vis.spatial.fx.FX3DPlugin
 import hep.dataforge.vis.spatial.fx.FXCanvas3D
-import hep.dataforge.vis.spatial.gdml.LUnit
-import hep.dataforge.vis.spatial.gdml.readFile
-import hep.dataforge.vis.spatial.gdml.toVisual
 import javafx.geometry.Orientation
 import javafx.scene.Parent
 import javafx.stage.FileChooser
-import scientifik.gdml.GDML
 import tornadofx.*
 
 class GDMLDemoApp : App(GDMLView::class)
@@ -38,24 +36,10 @@ class GDMLView : View() {
             buttonbar {
                 button("Load GDML") {
                     action {
-                        val file = chooseFile("Select a GDML file", filters = gdmlFilter).firstOrNull()
-                        if (file != null) {
-                            val obj = GDML.readFile(file.toPath()).toVisual {
-                                lUnit = LUnit.CM
-
-                                solidConfiguration = { parent, solid ->
-                                    if (solid.name == "cave") {
-                                        setProperty(Material3D.MATERIAL_WIREFRAME_KEY, true)
-                                    }
-                                    if (parent.physVolumes.isNotEmpty()) {
-                                        useStyle("opaque") {
-                                            Material3D.MATERIAL_OPACITY_KEY put 0.3
-                                        }
-                                    }
-                                }
-                            }
-                            canvas.render(obj)
-                        }
+                        val file = chooseFile("Select a GDML/json file", filters = fileNameFilter).firstOrNull()
+                            ?: return@action
+                        val visual: VisualGroup3D = Visual3DPlugin.readFile(file)
+                        canvas.render(visual)
                     }
                 }
             }
@@ -68,8 +52,11 @@ class GDMLView : View() {
     }
 
     companion object {
-        private val gdmlFilter = arrayOf(
-            FileChooser.ExtensionFilter("GDML", "*.gdml", "*.xml")
+        private val fileNameFilter = arrayOf(
+            FileChooser.ExtensionFilter("GDML", "*.gdml", "*.xml"),
+            FileChooser.ExtensionFilter("JSON", "*.json"),
+            FileChooser.ExtensionFilter("JSON.ZIP", "*.json.zip"),
+            FileChooser.ExtensionFilter("JSON.GZ", "*.json.gz")
         )
     }
 }
diff --git a/demo/gdml/src/jvmMain/kotlin/hep/dataforge/vis/spatial/gdml/demo/readFile.kt b/demo/gdml/src/jvmMain/kotlin/hep/dataforge/vis/spatial/gdml/demo/readFile.kt
new file mode 100644
index 00000000..11c4e162
--- /dev/null
+++ b/demo/gdml/src/jvmMain/kotlin/hep/dataforge/vis/spatial/gdml/demo/readFile.kt
@@ -0,0 +1,50 @@
+package hep.dataforge.vis.spatial.gdml.demo
+
+import hep.dataforge.vis.spatial.Material3D
+import hep.dataforge.vis.spatial.Visual3DPlugin
+import hep.dataforge.vis.spatial.VisualGroup3D
+import hep.dataforge.vis.spatial.gdml.LUnit
+import hep.dataforge.vis.spatial.gdml.readFile
+import hep.dataforge.vis.spatial.gdml.toVisual
+import scientifik.gdml.GDML
+import java.io.File
+import java.util.zip.GZIPInputStream
+import java.util.zip.ZipInputStream
+
+fun Visual3DPlugin.Companion.readFile(file: File): VisualGroup3D = when {
+    file.extension == "gdml" || file.extension == "xml" -> {
+        GDML.readFile(file.toPath()).toVisual {
+            lUnit = LUnit.CM
+
+            solidConfiguration = { parent, solid ->
+                if (solid.name == "cave") {
+                    setProperty(Material3D.MATERIAL_WIREFRAME_KEY, true)
+                }
+                if (parent.physVolumes.isNotEmpty()) {
+                    useStyle("opaque") {
+                        Material3D.MATERIAL_OPACITY_KEY put 0.3
+                    }
+                }
+            }
+        }
+    }
+    file.extension == "json" -> Visual3DPlugin.json
+        .parse(VisualGroup3D.serializer(), file.readText())
+    file.name.endsWith("json.zip") -> {
+        file.inputStream().use {
+            val unzip = ZipInputStream(it, Charsets.UTF_8)
+            val text = unzip.readAllBytes().decodeToString()
+            json.parse(VisualGroup3D.serializer(), text)
+        }
+    }
+    file.name.endsWith("json.gz") -> {
+        file.inputStream().use {
+            val unzip = GZIPInputStream(it)
+            val text = unzip.readAllBytes().decodeToString()
+            json.parse(VisualGroup3D.serializer(), text)
+        }
+    }
+    else -> error("Unknown extension ${file.extension}")
+}
+
+fun Visual3DPlugin.Companion.readFile(fileName: String): VisualGroup3D = readFile(File(fileName))
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