feat: add seam band width control and integrate with displacement logic for improved blending

js/displacement.js

@@ -124,8 +124,9 @@ export function applyDisplacement(geometry, imageData, imgWidth, imgHeight, sett
     let czX = 0, czY = 0, czZ = 0;
     if (settings.mappingMode === 6 && faceArea > 1e-12) {
       const cubicBlend = settings.mappingBlend ?? 0;
+      const cubicBandWidth = settings.seamBandWidth ?? 0.35;
       const unitFaceNrm = { x: faceNrm.x / faceArea, y: faceNrm.y / faceArea, z: faceNrm.z / faceArea };
-      const w = getCubicBlendWeights(unitFaceNrm, cubicBlend);
+      const w = getCubicBlendWeights(unitFaceNrm, cubicBlend, cubicBandWidth);
       czX = w.x * faceArea;
       czY = w.y * faceArea;
       czZ = w.z * faceArea;

js/main.js

@@ -51,6 +51,7 @@ const settings = {
   bottomAngleLimit: 5,
   topAngleLimit:    0,
   mappingBlend:     1,
+  seamBandWidth:    0.5,
   symmetricDisplacement: false,
 };
 
@@ -100,6 +101,8 @@ const bottomAngleLimitVal    = document.getElementById('bottom-angle-limit-val')
 const topAngleLimitVal       = document.getElementById('top-angle-limit-val');
 const seamBlendSlider        = document.getElementById('seam-blend');
 const seamBlendVal           = document.getElementById('seam-blend-val');
+const seamBandWidthSlider    = document.getElementById('seam-band-width');
+const seamBandWidthVal       = document.getElementById('seam-band-width-val');
 const symmetricDispToggle    = document.getElementById('symmetric-displacement');
 
 // ── Exclusion panel DOM refs ──────────────────────────────────────────────────
@@ -166,6 +169,7 @@ scaleVVal.value = posToScale(parseFloat(scaleVSlider.value));
 loadPresets().then(presets => {
   PRESETS = presets;
   buildPresetGrid();
+  loadDefaultCube();
   // Select Crystal as the default preset
   const noiseIdx = PRESETS.findIndex(p => p.name === 'Crystal');
   const defaultIdx = noiseIdx !== -1 ? noiseIdx : 0;
@@ -312,6 +316,7 @@ function wireEvents() {
   linkSlider(bottomAngleLimitSlider, bottomAngleLimitVal, v => { settings.bottomAngleLimit = v; return v; });
   linkSlider(topAngleLimitSlider,    topAngleLimitVal,    v => { settings.topAngleLimit    = v; 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', () => {
     settings.symmetricDisplacement = symmetricDispToggle.checked;
     updatePreview();
@@ -675,6 +680,62 @@ function formatM(n) {
 
 // ── STL loading ───────────────────────────────────────────────────────────────
 
+function loadDefaultCube() {
+  // Create a 50×50×50 mm box; convert to non-indexed so it behaves like a
+  // real STL (buildAdjacency and displacement expect non-indexed geometry).
+  const geo = new THREE.BoxGeometry(50, 50, 50).toNonIndexed();
+  geo.computeBoundingBox();
+  geo.computeVertexNormals();
+
+  currentGeometry = geo;
+  currentBounds   = computeBounds(geo);
+  currentStlName  = 'cube_50x50x50';
+  checkAmplitudeWarning();
+
+  loadGeometry(geo);
+  dropHint.classList.add('hidden');
+
+  // Reset exclusion state
+  excludedFaces     = new Set();
+  exclusionTool     = null;
+  eraseMode         = false;
+  isPainting        = false;
+  exclBrushBtn.classList.remove('active');
+  exclBucketBtn.classList.remove('active');
+  exclEraseToggle.classList.remove('active');
+  exclBrushTypeRow.classList.add('hidden');
+  exclRadiusRow.classList.add('hidden');
+  exclThresholdRow.classList.add('hidden');
+  canvas.style.cursor = '';
+  setExclusionOverlay(null);
+  setHoverPreview(null);
+  _lastHoverTriIdx = -1;
+  exclCount.textContent = t('excl.initExcluded');
+
+  const adjData = buildAdjacency(geo);
+  triangleAdjacency = adjData.adjacency;
+  triangleCentroids = adjData.centroids;
+
+  settings.scaleU  = 0.5; scaleUSlider.value = scaleToPos(0.5); scaleUVal.value = 0.5;
+  settings.scaleV  = 0.5; scaleVSlider.value = scaleToPos(0.5); scaleVVal.value = 0.5;
+  settings.offsetU = 0; offsetUSlider.value = 0; offsetUVal.value = 0;
+  settings.offsetV = 0; offsetVSlider.value = 0; offsetVVal.value = 0;
+  triLimitWarning.classList.add('hidden');
+
+  const maxDim = Math.max(currentBounds.size.x, currentBounds.size.y, currentBounds.size.z);
+  const defaultEdge = Math.max(0.05, Math.min(5.0, +(maxDim / 200).toFixed(2)));
+  settings.refineLength = defaultEdge;
+  refineLenSlider.value = defaultEdge;
+  refineLenVal.value = defaultEdge;
+
+  const triCount = getTriangleCount(geo);
+  const mb = ((geo.attributes.position.array.byteLength) / 1024 / 1024).toFixed(2);
+  meshInfo.textContent = t('ui.meshInfo', { n: triCount.toLocaleString(), mb });
+
+  exportBtn.disabled = (activeMapEntry === null);
+  updatePreview();
+}
+
 async function handleSTL(file) {
   try {
     const { geometry, bounds } = await loadSTLFile(file);

js/mapping.js

@@ -37,7 +37,7 @@ export function isAmbiguousCubicNormal(normal) {
   return primary - secondary <= CUBIC_AXIS_EPSILON;
 }
 
-export function getCubicBlendWeights(normal, blend) {
+export function getCubicBlendWeights(normal, blend, seamBandWidth = 0.35) {
   const axis = getDominantCubicAxis(normal);
   const ax = Math.abs(normal.x);
   const ay = Math.abs(normal.y);
@@ -61,7 +61,7 @@ export function getCubicBlendWeights(normal, blend) {
 
   // Only blend inside a seam band around the cube-face boundary. This keeps
   // strongly dominant faces fully textured even when the slider is barely on.
-  const seamWidth = Math.max(blend * 0.35, CUBIC_AXIS_EPSILON * 2);
+  const seamWidth = Math.max(seamBandWidth, CUBIC_AXIS_EPSILON * 2);
   const seamMixRaw = 1 - Math.min(1, Math.max(0, (primary - secondary) / seamWidth));
   const seamMix = blend * seamMixRaw * seamMixRaw * (3 - 2 * seamMixRaw);
   if (seamMix <= 0.001) return oneHot;
@@ -183,7 +183,7 @@ export function computeUV(pos, normal, mode, settings, bounds) {
     }
 
     case MODE_CUBIC: {
-      const weights = getCubicBlendWeights(normal, settings.mappingBlend ?? 0.0);
+      const weights = getCubicBlendWeights(normal, settings.mappingBlend ?? 0.0, settings.seamBandWidth ?? 0.35);
       const tYZ = applyTransform((pos.y - min.y) / md, (pos.z - min.z) / md, scaleU, scaleV, offsetU, offsetV, rotRad);
       const tXZ = applyTransform((pos.x - min.x) / md, (pos.z - min.z) / md, scaleU, scaleV, offsetU, offsetV, rotRad);
       const tXY = applyTransform((pos.x - min.x) / md, (pos.y - min.y) / md, scaleU, scaleV, offsetU, offsetV, rotRad);

js/previewMaterial.js

@@ -55,6 +55,7 @@ const fragmentShader = /* glsl */`
   uniform float     bottomAngleLimit; // degrees from horizontal; 0 = disabled
   uniform float     topAngleLimit;    // degrees from horizontal; 0 = disabled
   uniform float     mappingBlend;     // 0 = sharp seams, 1 = fully blended
+  uniform float     seamBandWidth;    // width of the blend zone near cube-face seams
   uniform int       symmetricDisplacement; // 1 = remap [0,1]→[-1,1] so 50% grey = no disp
 
   varying vec3 vModelPos;
@@ -91,7 +92,7 @@ const fragmentShader = /* glsl */`
                 : axis == 1 ? vec3(0.0, 1.0, 0.0)
                             : vec3(0.0, 0.0, 1.0);
 
-    float seamWidth = max(mappingBlend * 0.35, CUBIC_AXIS_EPSILON * 2.0);
+    float seamWidth = max(seamBandWidth, CUBIC_AXIS_EPSILON * 2.0);
     float seamMixRaw = 1.0 - clamp((primary - secondary) / seamWidth, 0.0, 1.0);
     float seamMix = mappingBlend * seamMixRaw * seamMixRaw * (3.0 - 2.0 * seamMixRaw);
     if (seamMix <= 0.001) return oneHot;
@@ -290,6 +291,7 @@ export function updateMaterial(material, displacementTexture, settings) {
   u.bottomAngleLimit.value = settings.bottomAngleLimit ?? 5.0;
   u.topAngleLimit.value    = settings.topAngleLimit    ?? 0.0;
   u.mappingBlend.value            = settings.mappingBlend            ?? 0.0;
+  u.seamBandWidth.value           = settings.seamBandWidth           ?? 0.35;
   u.symmetricDisplacement.value   = settings.symmetricDisplacement   ? 1 : 0;
 }
 
@@ -314,6 +316,7 @@ function buildUniforms(tex, settings) {
     bottomAngleLimit: { value: settings.bottomAngleLimit ?? 5.0 },
     topAngleLimit:    { value: settings.topAngleLimit    ?? 0.0 },
     mappingBlend:             { value: settings.mappingBlend            ?? 0.0 },
+    seamBandWidth:            { value: settings.seamBandWidth            ?? 0.35 },
     symmetricDisplacement:    { value: settings.symmetricDisplacement   ? 1 : 0 },
   };
 }

js/viewer.js

@@ -341,6 +341,7 @@ export function setSceneBackground(hexColor) {
 export function setViewerTheme(isLight) {
   if (!scene) return;
   scene.background = new THREE.Color(isLight ? 0xf0f0f5 : 0x111114);
+  const savedZ = grid ? grid.position.z : 0;
   if (grid) {
     scene.remove(grid);
     grid.geometry.dispose();
@@ -352,7 +353,7 @@ export function setViewerTheme(isLight) {
     isLight ? 0xd0d0e0 : 0x1e1e24
   );
   grid.rotation.x = Math.PI / 2;
-  grid.position.z = 0;
+  grid.position.z = savedZ;
   scene.add(grid);
 }