# phenom120

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2. ## Question on finding contact point

I am developing a simply 2d physics engine and I' ve read the source code of box2d and matter.js. I found some insteresting thing on finding contact point: Box2d use indicent edge, reference edge and clip to determine a contact point. It's very complex method and hard to understand. However, matter.js use a very simply method to do the same thing. just find the vertex that contained by opposite polygon with hill-climbing: var verticesB = SAT._findSupports(bodyA, bodyB, collision.normal), supports = []; // find the supports from bodyB that are inside bodyA if (Vertices.contains(bodyA.vertices, verticesB[0])) supports.push(verticesB[0]); if (Vertices.contains(bodyA.vertices, verticesB[1])) supports.push(verticesB[1]); // find the supports from bodyA that are inside bodyB if (supports.length < 2) { var verticesA = SAT._findSupports(bodyB, bodyA, Vector.neg(collision.normal)); if (Vertices.contains(bodyB.vertices, verticesA[0])) supports.push(verticesA[0]); if (supports.length < 2 && Vertices.contains(bodyB.vertices, verticesA[1])) supports.push(verticesA[1]); } and it works well in demo. My question is: why does box2d use such complex method? It's clear that matter.js's method is better. Or there are some potential shortcomings in matter.js's method?
3. ## Question about collision resolution

Thanks. I just realized that you are the author of first article
4. ## Question about collision resolution

It is quite useful, thank you. So, can i consider the first approach as a simplified approach of the second approach? And I don't know what is sequential impulses, Is it another approach of collision resolution?
5. ## Question about collision resolution

I'm currently implementing a 2D physics engine, then i stuck in collision resolution. So i did a search in google, and i found this passage, It explains how to use impulse to separate two objects. But after that, i found another another passage, this article is very complicated, but they seem talking the same thing ——— how to implementing the collision resolution. So now, what i confuse is why are there two completely different approaches of collision resolution? What's the difference between them? Which approaches is right? I am not a native english speakers, so i hope you can understand what i wrote. Thanks.