Model viewer working with all default pack models

nonpacks/static/js/geo_builder.js

@@ -202,13 +202,24 @@
                 var origin = c.origin || [0, 0, 0];
                 var size = c.size || [1, 1, 1];
                 var cRot = (c.rotation || [0, 0, 0]).map(function (d) { return -d * DEG; });
+                var hasRot = !!(c.rotation && (c.rotation[0] || c.rotation[1] || c.rotation[2]));
+                // Blockbench cubes rotate around their own pivot (fall back to origin).
+                var cPivot = hasRot ? (c.pivot || origin) : origin;
+                var center = [
+                    origin[0] + size[0] / 2,
+                    origin[1] + size[1] / 2,
+                    origin[2] + size[2] / 2,
+                ];
                 var cubeWorld = multiply(
                     world,
                     multiply(
-                        translation(origin[0], origin[1], origin[2]),
+                        translation(cPivot[0], cPivot[1], cPivot[2]),
                         multiply(
                             rotationXYZ(cRot[0], cRot[1], cRot[2]),
-                            translation(size[0] / 2, size[1] / 2, size[2] / 2)
+                            multiply(
+                                translation(-cPivot[0], -cPivot[1], -cPivot[2]),
+                                translation(center[0], center[1], center[2])
+                            )
                         )
                     )
                 );

nonpacks/static/js/tests/geo_builder.test.js

@@ -148,6 +148,24 @@ for (const w of wolfCenters) {
 assert(wTail.center[2] > 8, `wolf tail behind body (z=${wTail.center[2].toFixed(1)})`);
 assert(wBody && wTail.center[2] > wBody.center[2], 'tail z > body z');
 
+// ---------- 5. Real polar bear: cube-level pivot + rotation ----------
+// The polar bear's rear torso cube has its own pivot/rotation; rotating around
+// the cube origin (not its pivot) sent it flying to z≈48. Regression test.
+const polar = require(path.join(__dirname, 'fixtures', 'polar_bear.geo.json'));
+const polarBuilt = GeoBuilder.build(polar);
+const polarCubes = polarBuilt.cubes.map(c => ({ c, center: worldCenter(c.matrix) }));
+const pRear = polarCubes.find(({ c }) => c.size[0] === 18.2 && c.size[1] === 18.2 && c.size[2] === 14.3);
+assert(!!pRear, 'polar bear rear torso cube found');
+if (pRear) {
+    assertVec(pRear.center, [0, 17.55, 7.8], 'polar bear rear torso center (expect (0,17.55,7.8))');
+}
+const pFront = polarCubes.find(({ c }) => c.size[0] === 15.6 && c.size[1] === 15.6 && c.size[2] === 13);
+if (pFront) {
+    // Rear torso sits behind and at the same height as the front torso.
+    assert(pRear.center[2] > pFront.center[2], 'rear torso behind front torso');
+    assert(approx(pRear.center[1], pFront.center[1], 1.5), 'rear + front torso at similar height');
+}
+
 // ---------- summary ----------
 if (failures === 0) {
     console.log(`geo_builder tests OK (${checks} checks)`);