From 467842ba0bc438e926727d6a985a281e56433ec9 Mon Sep 17 00:00:00 2001
From: Georg Tomitsch <georg@tomitsch.net>
Date: Fri, 5 Jun 2026 11:48:01 +0200
Subject: [PATCH] Checkpoint flip page dimensions

---
 public/js/webgl-book-shape-lab.js | 19 +++++--------------
 public/webgl-book-shape-lab.html  |  2 +-
 2 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/public/js/webgl-book-shape-lab.js b/public/js/webgl-book-shape-lab.js
index 4bc25af..710c2a6 100644
--- a/public/js/webgl-book-shape-lab.js
+++ b/public/js/webgl-book-shape-lab.js
@@ -1027,8 +1027,8 @@ function updateActiveFlips(now) {
 function buildFlippingPageSurface(sourceLine, destinationLine, direction, t, pageOffset = 0) {
     const widthSegments = sourceLine.points.length - 1;
     const depthSegments = 18;
-    const zFront = lastBookModel.pageDepth * 0.5 + 0.018;
-    const zBack = -lastBookModel.pageDepth * 0.5 - 0.018;
+    const zFront = lastBookModel.pageDepth * 0.5;
+    const zBack = -lastBookModel.pageDepth * 0.5;
     if (t <= 0) return createRestingPageSurface(sourceLine.points, depthSegments, zFront, zBack);
     if (t >= 1) return createRestingPageSurface(destinationLine.points, depthSegments, zFront, zBack);
 
@@ -1039,11 +1039,12 @@ function buildFlippingPageSurface(sourceLine, destinationLine, direction, t, pag
     const baseAngle = startAngle + direction * Math.PI * t;
     const lift = Math.sin(Math.PI * t);
     const curlStrength = direction * 0.48 * lift;
-    const sourceLengths = cumulativeLineLengths(sourceLine.points);
+    const sourceAnchor = sourceLine.anchor;
     const surface = [];
     for (let widthIndex = 0; widthIndex <= widthSegments; widthIndex += 1) {
         const u = widthIndex / widthSegments;
-        const radius = sourceLengths[widthIndex];
+        const sourcePoint = sourceLine.points[widthIndex];
+        const radius = Math.max(0, sourceSide * (sourcePoint.x - sourceAnchor.x));
         const row = [];
         for (let depthIndex = 0; depthIndex <= depthSegments; depthIndex += 1) {
             const v = depthIndex / depthSegments;
@@ -1066,16 +1067,6 @@ function buildFlippingPageSurface(sourceLine, destinationLine, direction, t, pag
     return surface;
 }
 
-function cumulativeLineLengths(points) {
-    const lengths = [0];
-    for (let index = 1; index < points.length; index += 1) {
-        const previous = points[index - 1];
-        const current = points[index];
-        lengths.push(lengths[index - 1] + Math.hypot(current.x - previous.x, current.y - previous.y));
-    }
-    return lengths;
-}
-
 function createRestingPageSurface(points, depthSegments, zFront, zBack) {
     return points.map((point) => {
         const row = [];
diff --git a/public/webgl-book-shape-lab.html b/public/webgl-book-shape-lab.html
index 58e1a26..14a5fcd 100644
--- a/public/webgl-book-shape-lab.html
+++ b/public/webgl-book-shape-lab.html
@@ -74,6 +74,6 @@
         <button id="fast_forward" type="button">Fast Forward</button>
         <output id="flip_count">0 / 10</output>
     </div>
-    <script type="module" src="/js/webgl-book-shape-lab.js?v=packed-spine-seam-2"></script>
+    <script type="module" src="/js/webgl-book-shape-lab.js?v=flip-sheet-dimensions-1"></script>
 </body>
 </html>