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    <p>I first thought the problem could come from the change of slope between two adjacent segments, but since on a flat surface of polygons you still have bumps I think the problem is rather hitting the corner of a polygon.</p> <p>I don't know if you can set two sets of polygons, overlapping each other ? Just use the same interpolation calculations and generate a second set of polygons just like in the diagram hereafter : you have the red set of polygons built and add the green set by setting the left vertices of a green polygon in the middle of a red polygon, and its right vertices in the middle of the next red polygon.</p> <p>![diagram][1]</p> <p>This should work on concave curves and... well you should be flying over the convex ones anyway.</p> <p>If this doesn't work try setting a big number of polygons to build the slope. Use a tenth of the circle's radius for the polygon's width, maybe even less. That should reduce your slope discontinuities.</p> <h2>-- Edit</h2> <p>In Box2D.js line 5082 (in <a href="http://code.google.com/searchframe#fbVL2fD7rV0/trunk/Box2D.js" rel="nofollow">this repo</a> at least) you have the PreSolve(contact, manifold) function that you can override to check if the manifolds (directions in which the snowball are impulsed when colliding the polygons) are correct.</p> <p>To do so, you would need to recover the manifold vector and compare it to the normal of the curve. It should look like that (maybe not exactly) : </p> <pre><code>Box2D.Dynamics.b2ContactListener.prototype.PreSolve = function (contact, oldManifold) { // contact instanceof Box2D.Dynamics.Contacts.b2Contact == true var localManifold, worldManifold, xA, xB, man_vect, curve_vect, normal_vect, angle; localManifold = contact.GetManifold(); if(localManifold.m_pointCount == 0) return; // or raise an exception worldManifold = new Box2D.Collision.b2WorldManifold(); contact.GetWorldManifold( worldManifold ); // deduce the impulse direction from the manifold points man_vect = worldManifold.m_normal.Copy(); // we need two points close to &amp; surrounding the collision to compute the normal vector // not sure this is the right order of magnitude xA = worldManifold.m_points[0].x - 0.1; xB = worldManifold.m_points[0].x + 0.1; man_vect.Normalize(); // now we have the abscissas let's get the ordinate of these points on the curve // the subtraction of these two points will give us a vector parallel to the curve var SmoothConfig; SmoothConfig = { params: { method: 'cubic', clip: 'mirror', cubicTension: 0, deepValidation: false }, options: { averageLineLength: .5 } } // get the points, smooth and smooth config stuff here smooth = Smooth(global_points,SmoothConfig); curve_vect = new Box2D.Common.Math.b2Vec2(xB, smooth(xB)[1]); curve_vect.Subtract(new Box2D.Common.Math.b2Vec2(xA, smooth(xA)[1])); // now turn it to have a normal vector, turned upwards normal_vect = new Box2D.Common.Math.b2Vec2(-curve_vect.y, curve_vect.x); if(normal_vect.y &gt; 0) normal_vect.NegativeSelf(); normal_vect.Normalize(); worldManifold.m_normal = normal_vect.Copy(); // and finally compute the angle between the two vectors angle = Box2D.Common.Math.b2Math.Dot(man_vect, normal_vect); $('#angle').text("" + Math.round(Math.acos(angle)*36000/Math.PI)/100 + "°"); // here try to raise an exception if the angle is too big (maybe after a few ms) // with different thresholds on the angle value to see if the bumps correspond // to a manifold that's not normal enough to your curve }; </code></pre>
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    1. POJavascript physics engine and simulated infinite curve
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    1. COThanks for the idea, but I couldn't implement it. It was still bumping.
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    2. COI still think the corners of your boxes are the problem. See http://www.iforce2d.net/b2dtut/collision-anatomy - obviously you would want your snowball to bounce of a segment with an impulse normal to its surface. When hitting a corner, that's not what happens. Try setting the snowball to a bullet body (see http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?t=5073#p18530 ).
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    3. COI updated the post with your comment in mind.
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