diff --git a/src/viewport-three/viewport-layout.ts b/src/viewport-three/viewport-layout.ts
new file mode 100644
index 00000000..6b3199ae
--- /dev/null
+++ b/src/viewport-three/viewport-layout.ts
@@ -0,0 +1,75 @@
+import type { ViewportViewMode } from "./viewport-view-modes";
+
+export type ViewportLayoutMode = "single" | "quad";
+
+export type ViewportDisplayMode = "normal" | "authoring";
+
+export type ViewportPanelId = "topLeft" | "topRight" | "bottomLeft" | "bottomRight";
+
+export const VIEWPORT_LAYOUT_MODES = ["single", "quad"] as const;
+
+export const VIEWPORT_PANEL_IDS = ["topLeft", "topRight", "bottomLeft", "bottomRight"] as const;
+
+export interface ViewportPanelState {
+  viewMode: ViewportViewMode;
+  displayMode: ViewportDisplayMode;
+}
+
+export interface ViewportLayoutState {
+  layoutMode: ViewportLayoutMode;
+  activePanelId: ViewportPanelId;
+  panels: Record<ViewportPanelId, ViewportPanelState>;
+}
+
+export const DEFAULT_VIEWPORT_LAYOUT_STATE: ViewportLayoutState = {
+  layoutMode: "single",
+  activePanelId: "topLeft",
+  panels: {
+    topLeft: {
+      viewMode: "perspective",
+      displayMode: "normal"
+    },
+    topRight: {
+      viewMode: "top",
+      displayMode: "authoring"
+    },
+    bottomLeft: {
+      viewMode: "front",
+      displayMode: "authoring"
+    },
+    bottomRight: {
+      viewMode: "side",
+      displayMode: "authoring"
+    }
+  }
+};
+
+const VIEWPORT_PANEL_LABELS: Record<ViewportPanelId, string> = {
+  topLeft: "Top Left",
+  topRight: "Top Right",
+  bottomLeft: "Bottom Left",
+  bottomRight: "Bottom Right"
+};
+
+const VIEWPORT_LAYOUT_MODE_LABELS: Record<ViewportLayoutMode, string> = {
+  single: "Single View",
+  quad: "4-Panel"
+};
+
+const VIEWPORT_DISPLAY_MODE_LABELS: Record<ViewportDisplayMode, string> = {
+  normal: "Normal",
+  authoring: "Authoring"
+};
+
+export function getViewportPanelLabel(panelId: ViewportPanelId): string {
+  return VIEWPORT_PANEL_LABELS[panelId];
+}
+
+export function getViewportLayoutModeLabel(layoutMode: ViewportLayoutMode): string {
+  return VIEWPORT_LAYOUT_MODE_LABELS[layoutMode];
+}
+
+export function getViewportDisplayModeLabel(displayMode: ViewportDisplayMode): string {
+  return VIEWPORT_DISPLAY_MODE_LABELS[displayMode];
+}
+