camera: bank the view when the flight path curves

vendor/clouds3d.js

@@ -1428,6 +1428,13 @@ var CAM_CFG = (window.CONFIG && window.CONFIG.camera) || {};
 var CAM_AIM_MOON = (CAM_CFG.aim === 'moon');
 var CAM_AIM_EASE = (typeof CAM_CFG.aimEase === 'number') ? Math.max(0, Math.min(0.999, CAM_CFG.aimEase)) : 0.94;
 var CAM_AIM_BOB = (typeof CAM_CFG.aimBob === 'number') ? Math.max(0, Math.min(1, CAM_CFG.aimBob)) : 0.25;
+var CAM_ROLL_CFG = CAM_CFG.roll || {};
+var CAM_ROLL_ON = CAM_ROLL_CFG.enabled !== false;
+var CAM_ROLL_GAIN = (typeof CAM_ROLL_CFG.gain === 'number') ? Math.max(0, CAM_ROLL_CFG.gain) : 12;
+var CAM_ROLL_MAX = (typeof CAM_ROLL_CFG.maxDeg === 'number') ? Math.max(0, Math.min(35, CAM_ROLL_CFG.maxDeg)) * Math.PI / 180 : 12 * Math.PI / 180;
+var CAM_ROLL_EASE = (typeof CAM_ROLL_CFG.ease === 'number') ? Math.max(0, Math.min(0.999, CAM_ROLL_CFG.ease)) : 0.92;
+var CAM_ROLL_SIGN = (typeof CAM_ROLL_CFG.sign === 'number') ? CAM_ROLL_CFG.sign : -1;
+var lastCamBearing = null, lastCamTime = null, camRoll = 0;
 var aimHdX = 0, aimHdZ = 1, aimPitch = 0.45, aimReady = false;
 // CONFIG.clouds = { top: ..., bottom: ... } overrides the defaults; the
 // deck must stay below the camera and keep a minimum thickness.
@@ -6243,7 +6250,29 @@ window.clouds3dRender = function(target) {
     // View direction as compass bearing (world +X = east, +Z = north,
     // matching the sun-vector convention): 0 = north, clockwise.
     // The clock's compass needle reads this.
-    window.__flightBearing = Math.atan2(hdX, hdZ);
+    var flightBearing = Math.atan2(hdX, hdZ);
+    window.__flightBearing = flightBearing;
+    var viewRoll = 0;
+    if (CAM_ROLL_ON) {
+        if (lastCamBearing !== null && lastCamTime !== null) {
+            var _dt = Math.max(0.001, now - lastCamTime);
+            var _db = flightBearing - lastCamBearing;
+            while (_db > Math.PI) _db -= 2 * Math.PI;
+            while (_db < -Math.PI) _db += 2 * Math.PI;
+            var _turnRate = _db / _dt;
+            var _target = CAM_ROLL_SIGN * _turnRate * CAM_ROLL_GAIN;
+            if (_target > CAM_ROLL_MAX) _target = CAM_ROLL_MAX;
+            else if (_target < -CAM_ROLL_MAX) _target = -CAM_ROLL_MAX;
+            camRoll += (_target - camRoll) * (1 - CAM_ROLL_EASE);
+        }
+        lastCamBearing = flightBearing;
+        lastCamTime = now;
+        viewRoll = camRoll;
+    } else {
+        lastCamBearing = null;
+        lastCamTime = null;
+        camRoll = 0;
+    }
     // Periodic check: when the camera approaches the corridor edge,
     // re-centre the mosaic (whole-tile shift of the canvas content +
     // fetch the newly exposed columns). At uSpeed=1 the camera moves
@@ -6309,10 +6338,20 @@ window.clouds3dRender = function(target) {
     // Debug override: point at world origin so the mesh is always in view.
     var fwdLen = Math.hypot(hdX, pitch, hdZ) || 1;
     var fwdX = hdX / fwdLen, fwdY = -pitch / fwdLen, fwdZ = hdZ / fwdLen;
+    var upX = 0, upY = 1, upZ = 0;
+    if (Math.abs(viewRoll) > 1e-5) {
+        var _rc = Math.cos(viewRoll), _rs = Math.sin(viewRoll);
+        // Rodrigues rotation of the world-up vector around the forward axis.
+        upX = -fwdZ * _rs;
+        upY = _rc;
+        upZ = fwdX * _rs;
+        var _ul = Math.hypot(upX, upY, upZ) || 1;
+        upX /= _ul; upY /= _ul; upZ /= _ul;
+    }
     var view = mat4LookAt(
         [camX, camY, camZ],
         [camX + fwdX * 5, camY + fwdY * 5, camZ + fwdZ * 5],
-        [0, 1, 0]
+        [upX, upY, upZ]
     );
     // Inverse of (proj * view) is uploaded to the cloud/sky shader so
     // both can reconstruct the world ray from gl_FragCoord identically