diff --git a/js/main.js b/js/main.js
index 9063339..ad08ea8 100644
--- a/js/main.js
+++ b/js/main.js
@@ -26,6 +26,8 @@ let previewDebounce   = null;
 // Boundary edge data texture for per-fragment falloff in bump-only preview
 let _boundaryEdgeTex   = null;
 let _boundaryEdgeCount = 0;
+let _falloffDirty      = true;   // recompute falloff on next updateFaceMask
+let _falloffGeometry   = null;   // geometry the falloff was last computed for
 
 // ── Exclusion state ───────────────────────────────────────────────────────────
 let excludedFaces      = new Set();   // triangle indices in currentGeometry
@@ -331,11 +333,11 @@ function wireEvents() {
   linkSlider(rotationSlider,  rotationVal,  v => { settings.rotation  = v; return Math.round(v); });
   linkSlider(amplitudeSlider, amplitudeVal, v => { settings.amplitude = v; checkAmplitudeWarning(); return v.toFixed(2); });
   amplitudeVal.addEventListener('change', checkAmplitudeWarning);
-  linkSlider(boundaryFalloffSlider, boundaryFalloffVal, v => { settings.boundaryFalloff = v; return v.toFixed(1); });
+  linkSlider(boundaryFalloffSlider, boundaryFalloffVal, v => { settings.boundaryFalloff = v; _falloffDirty = true; return v.toFixed(1); });
   linkSlider(refineLenSlider, refineLenVal, v => { settings.refineLength  = v; return v.toFixed(2); }, false);
   linkSlider(maxTriSlider, maxTriVal, v => { settings.maxTriangles = v; return formatM(v); }, false);
-  linkSlider(bottomAngleLimitSlider, bottomAngleLimitVal, v => { settings.bottomAngleLimit = v; return v; });
-  linkSlider(topAngleLimitSlider,    topAngleLimitVal,    v => { settings.topAngleLimit    = v; return v; });
+  linkSlider(bottomAngleLimitSlider, bottomAngleLimitVal, v => { settings.bottomAngleLimit = v; _falloffDirty = true; return v; });
+  linkSlider(topAngleLimitSlider,    topAngleLimitVal,    v => { settings.topAngleLimit    = v; _falloffDirty = true; return v; });
   linkSlider(seamBlendSlider,        seamBlendVal,        v => { settings.mappingBlend     = v; return v.toFixed(2); });
   linkSlider(seamBandWidthSlider,    seamBandWidthVal,    v => { settings.seamBandWidth    = v; return v.toFixed(2); });
   symmetricDispToggle.addEventListener('change', () => {
@@ -796,6 +798,7 @@ function handlePlaceOnFaceClick(e) {
 
 function refreshExclusionOverlay() {
   if (!currentGeometry) return;
+  _falloffDirty = true;
   if (selectionMode) {
     // Include Only mode: tint the complement (non-selected faces) with a pastel blue
     // so the model stays visible against the dark background before any faces are painted.
@@ -1146,8 +1149,12 @@ function updateFaceMask(geometry) {
     addFaceNormals(geometry);
   }
 
-  computeBoundaryFalloffAttr(geometry, maskArr);
-  computeBoundaryEdges(geometry, maskArr);
+  if (_falloffDirty || geometry !== _falloffGeometry) {
+    computeBoundaryFalloffAttr(geometry, maskArr);
+    computeBoundaryEdges(geometry, maskArr);
+    _falloffDirty = false;
+    _falloffGeometry = geometry;
+  }
   syncBoundaryEdgeUniforms();
 }
 
@@ -1388,7 +1395,7 @@ function computeBoundaryEdges(geometry, userMaskArr) {
     }
   }
 
-  const MAX_EDGES = 512;
+  const MAX_EDGES = 64;
   const edges = [];
   for (const [key, faces] of edgeFaces) {
     if (edges.length >= MAX_EDGES) break;
diff --git a/js/previewMaterial.js b/js/previewMaterial.js
index 492de5e..da75466 100644
--- a/js/previewMaterial.js
+++ b/js/previewMaterial.js
@@ -248,7 +248,7 @@ const fragmentShader = /* glsl */`
     // compute the distance from each pixel to the nearest boundary edge.
     if (useDisplacement == 0 && boundaryFalloffDist > 0.001 && boundaryEdgeCount > 0) {
       float minDist = boundaryFalloffDist;
-      for (int i = 0; i < 512; i++) {
+      for (int i = 0; i < 64; i++) {
         if (i >= boundaryEdgeCount) break;
         float uA = (float(i * 2) + 0.5) / boundaryEdgeTexWidth;
         float uB = (float(i * 2 + 1) + 0.5) / boundaryEdgeTexWidth;
@@ -258,7 +258,7 @@ const fragmentShader = /* glsl */`
         float abLen2 = dot(ab, ab);
         float t = clamp(dot(vModelPos - ea, ab) / max(abLen2, 1e-10), 0.0, 1.0);
         float d = length(vModelPos - (ea + t * ab));
-        minDist = min(minDist, d);
+        if (d < minDist) { minDist = d; if (d < 1e-4) break; }
       }
       maskBlend *= clamp(minDist / boundaryFalloffDist, 0.0, 1.0);
     }