diff --git a/index.html b/index.html
index 4800c88..a1ca840 100644
--- a/index.html
+++ b/index.html
@@ -44,6 +44,10 @@
       </div>
       <div id="viewport-footer">
         <span id="mesh-info" class="mesh-info"></span>
+        <label class="wireframe-toggle">
+          <input type="checkbox" id="wireframe-toggle" />
+          Wireframe
+        </label>
         <div class="viewport-controls-hint">Left drag: orbit &nbsp;·&nbsp; Right drag: pan &nbsp;·&nbsp; Scroll: zoom</div>
       </div>
     </section>
diff --git a/js/exporter.js b/js/exporter.js
index 53b5dc1..6e881b7 100644
--- a/js/exporter.js
+++ b/js/exporter.js
@@ -10,15 +10,10 @@ const exporter = new STLExporter();
  * @param {string} [filename]
  */
 export function exportSTL(geometry, filename = 'textured.stl') {
-  // The geometry was rotated -90° around X on load to convert Z-up → Y-up for the viewer.
-  // Undo that rotation before export so the STL lands back in the original Z-up orientation
-  // that 3D-print slicers expect.
-  const exportGeom = geometry.clone();
-  exportGeom.applyMatrix4(new THREE.Matrix4().makeRotationX(Math.PI / 2));
-
-  const mesh = new THREE.Mesh(exportGeom, new THREE.MeshBasicMaterial());
+  // Geometry is already in the original Z-up orientation (the loader never rotates it;
+  // the viewer uses a Z-up camera instead). Export as-is so slicers receive the correct pose.
+  const mesh = new THREE.Mesh(geometry, new THREE.MeshBasicMaterial());
   const result = exporter.parse(mesh, { binary: true });
-  exportGeom.dispose();
 
   // result is an ArrayBuffer in binary mode
   const blob = new Blob([result], { type: 'application/octet-stream' });
diff --git a/js/main.js b/js/main.js
index 561742e..0301982 100644
--- a/js/main.js
+++ b/js/main.js
@@ -1,4 +1,4 @@
-import { initViewer, loadGeometry, setMeshMaterial } from './viewer.js';
+import { initViewer, loadGeometry, setMeshMaterial, setWireframe } from './viewer.js';
 import { loadSTLFile, computeBounds, getTriangleCount }  from './stlLoader.js';
 import { PRESETS, loadCustomTexture }  from './presetTextures.js';
 import { createPreviewMaterial, updateMaterial } from './previewMaterial.js';
@@ -42,6 +42,7 @@ const exportProgress   = document.getElementById('export-progress');
 const exportProgBar    = document.getElementById('export-progress-bar');
 const exportProgLbl    = document.getElementById('export-progress-label');
 const triLimitWarning  = document.getElementById('tri-limit-warning');
+const wireframeToggle  = document.getElementById('wireframe-toggle');
 
 const mappingSelect   = document.getElementById('mapping-mode');
 const scaleUSlider    = document.getElementById('scale-u');
@@ -192,6 +193,9 @@ function wireEvents() {
 
   // ── Export ──
   exportBtn.addEventListener('click', handleExport);
+
+  // ── Wireframe ──
+  wireframeToggle.addEventListener('change', () => setWireframe(wireframeToggle.checked));
 }
 
 // ── Slider helper ─────────────────────────────────────────────────────────────
diff --git a/js/mapping.js b/js/mapping.js
index 66b925f..d4d681d 100644
--- a/js/mapping.js
+++ b/js/mapping.js
@@ -51,12 +51,27 @@ export function computeUV(pos, normal, mode, settings, bounds) {
     }
 
     case MODE_CYLINDRICAL: {
-      // Z is up: wrap around Z axis, height along Z
+      // Cylindrical around Z axis with automatic caps.
+      //
+      // Side: V arc-length-normalised by circumference C = 2πr so that
+      //   scaleU = scaleV gives un-stretched square texels on the surface.
+      //
+      // Cap (|normalZ| > 0.5): planar XY centred on the axis, scaled to the
+      //   diameter so one tile covers the full cap disc.
+      const r  = Math.max(size.x, size.y) * 0.5;
+      const C  = TWO_PI * Math.max(r, 1e-6);
       const rx = pos.x - center.x;
       const ry = pos.y - center.y;
-      const theta = Math.atan2(ry, rx);              // [-PI, PI]
-      u = (theta / TWO_PI) + 0.5;                    // [0, 1]
-      v = (pos.z - min.z) / Math.max(size.z, 1e-6);
+      if (Math.abs(normal.z) > 0.5) {
+        // Cap face — normalise by C so one tile = same world size as on the side
+        u = rx / C + 0.5;
+        v = ry / C + 0.5;
+      } else {
+        // Side face
+        const theta = Math.atan2(ry, rx);
+        u = (theta / TWO_PI) + 0.5;
+        v = (pos.z - min.z) / C;
+      }
       break;
     }
 
diff --git a/js/previewMaterial.js b/js/previewMaterial.js
index 495a215..d8b7787 100644
--- a/js/previewMaterial.js
+++ b/js/previewMaterial.js
@@ -77,10 +77,27 @@ const fragmentShader = /* glsl */`
       return sampleMap((pos.yz - boundsMin.yz) / max(boundsSize.yz, vec2(1e-4)));
 
     } else if (mappingMode == 3) {
-      // Cylindrical around Z axis (Z is up)
-      float u = atan(rel.y, rel.x) / TWO_PI + 0.5;
-      float v = (pos.z - boundsMin.z) / max(boundsSize.z, 1e-4);
-      return sampleMap(vec2(u, v));
+      // Cylindrical around Z axis (Z is up) with automatic caps.
+      //
+      // Side: V is arc-length-normalised (divided by circumference C = 2πr)
+      //   so that scaleU = scaleV gives square, un-stretched texels on the surface.
+      //
+      // Cap (|normalZ| > 0.5): planar XY centred on the cylinder axis, one tile
+      //   fills the diameter × diameter square so the disc looks fully textured.
+      float r = max(boundsSize.x, boundsSize.y) * 0.5;
+      float C = TWO_PI * max(r, 1e-4);
+      if (abs(vModelNormal.z) > 0.5) {
+        // Cap face — normalise by C so one tile = same world size as on the side
+        return sampleMap(vec2(
+          rel.x / C + 0.5,
+          rel.y / C + 0.5
+        ));
+      }
+      // Side face
+      return sampleMap(vec2(
+        atan(rel.y, rel.x) / TWO_PI + 0.5,
+        (pos.z - boundsMin.z) / C
+      ));
 
     } else if (mappingMode == 4) {
       // Spherical — Z is up
diff --git a/js/viewer.js b/js/viewer.js
index 42254e2..1dfa0d0 100644
--- a/js/viewer.js
+++ b/js/viewer.js
@@ -1,9 +1,14 @@
 import * as THREE from 'three';
 import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
+import { LineSegments2 }  from 'three/addons/lines/LineSegments2.js';
+import { LineSegmentsGeometry } from 'three/addons/lines/LineSegmentsGeometry.js';
+import { LineMaterial }   from 'three/addons/lines/LineMaterial.js';
 
 let renderer, camera, scene, controls, meshGroup, ambientLight, dirLight1, dirLight2, grid;
 let currentMesh = null;
 let axesGroup = null;
+let wireframeLines = null;   // LineSegments overlay, or null when hidden
+let wireframeVisible = false;
 
 // Build a labelled coordinate axes indicator scaled to `size`.
 // X = red, Y = green, Z = blue (up).
@@ -131,6 +136,13 @@ function onResize() {
   camera.left   = -halfH * aspect;
   camera.right  =  halfH * aspect;
   camera.updateProjectionMatrix();
+  // LineMaterial needs the actual pixel resolution to compute linewidth correctly
+  if (wireframeLines) {
+    wireframeLines.material.resolution.set(
+      w * renderer.getPixelRatio(),
+      h * renderer.getPixelRatio(),
+    );
+  }
 }
 
 /**
@@ -161,6 +173,11 @@ export function loadGeometry(geometry, material) {
   currentMesh.receiveShadow = true;
   meshGroup.add(currentMesh);
 
+  // Rebuild wireframe overlay to match the new geometry
+  // (old overlay is already gone because meshGroup was cleared above)
+  wireframeLines = null;
+  if (wireframeVisible) _buildWireframe(geometry);
+
   // Position grid at mesh bottom (Z-up: move grid along Z)
   geometry.computeBoundingBox();
   const box = geometry.boundingBox;
@@ -232,3 +249,51 @@ export function getRenderer() { return renderer; }
 export function getCamera()   { return camera; }
 export function getScene()    { return scene; }
 export function getCurrentMesh() { return currentMesh; }
+
+/**
+ * Show or hide the triangle-edge wireframe overlay.
+ * @param {boolean} enabled
+ */
+export function setWireframe(enabled) {
+  wireframeVisible = enabled;
+  if (enabled) {
+    if (!wireframeLines && currentMesh) _buildWireframe(currentMesh.geometry);
+    if (wireframeLines) wireframeLines.visible = true;
+  } else {
+    if (wireframeLines) wireframeLines.visible = false;
+  }
+}
+
+function _buildWireframe(geometry) {
+  // Dispose any stale overlay
+  if (wireframeLines) {
+    if (wireframeLines.parent) wireframeLines.parent.remove(wireframeLines);
+    wireframeLines.geometry.dispose();
+    wireframeLines.material.dispose();
+    wireframeLines = null;
+  }
+
+  // EdgesGeometry gives one segment per unique triangle edge
+  const edgesGeo = new THREE.EdgesGeometry(geometry, 1);
+
+  // Convert to LineSegmentsGeometry (required by LineMaterial / LineSegments2)
+  const lsGeo = new LineSegmentsGeometry().fromEdgesGeometry(edgesGeo);
+  edgesGeo.dispose();
+
+  const lsMat = new LineMaterial({
+    color: 0xffffff,
+    opacity: 0.75,
+    transparent: true,
+    linewidth: 1.5,          // pixels — works on all desktop GPUs
+    depthTest: true,
+    resolution: new THREE.Vector2(
+      renderer.domElement.width  * renderer.getPixelRatio(),
+      renderer.domElement.height * renderer.getPixelRatio(),
+    ),
+  });
+
+  wireframeLines = new LineSegments2(lsGeo, lsMat);
+  wireframeLines.renderOrder = 1;
+  // Add to meshGroup so it's automatically removed when a new model is loaded
+  meshGroup.add(wireframeLines);
+}
diff --git a/style.css b/style.css
index 2901843..cbe9cdf 100644
--- a/style.css
+++ b/style.css
@@ -145,6 +145,16 @@ main {
   color: #555566;
 }
 
+.wireframe-toggle {
+  display: flex;
+  align-items: center;
+  gap: 5px;
+  font-size: 11px;
+  color: var(--text-muted);
+  cursor: pointer;
+  user-select: none;
+}
+
 /* ── Settings panel ──────────────────────────────────────────────────── */
 #settings-panel {
   width: var(--sidebar-w);