The cocos2d-x engine supports two physical engines, box2d and chipmunk, respectively. It is usually used as box2d. The concepts in box2d are as follows. World, body, bodydef, fixture, fixturedef, shape, and joint) and link definition (jointdef ). World: two steps are required to create a world: 1. Generate a Gravity Vector. 2. generate an object based on the gravity vector. For example: // generate a Gravity Vector b2vec2 gravity; gravity. set (0.0f,-10.0f); // generates the world object b2world * World = new b2world (gravity, true) based on the gravity vector ); Rigid Body and rigid body definition: a rigid body represents a particle, so it has only a position and no size. There are three types of rigid bodies: 1. Static rigid bodies ). No quality, no speed. Absolutely static. 2. prismatic body ). No quality, but speed. The engine calculates and updates its location based on the speed. 3. dynamic body ). Quality and speed. The most common rigid body. Similar to the world, a rigid body definition can be divided into two steps: 1. Create a rigid body definition. 2. Generate a rigid body according to the cylinder definition. Eg: // generate a rigid body definition b2bodydef groundbodydef; groundbodydef. position. Set (0, 0); // generate a rigid body b2body * groundbody = World-> createbody (& groundbodydef) based on the rigid body definition ); Shape: The shape is attached to the rigid body by association, and the rigid body has a visual shape. A rigid body can have multiple associations, so it can have multiple shapes. box2d is called a compound shapes to form more complex shapes. Eg: b2polygonshape dynamicbox; dynamicbox. setasbox (0.5f, 0.5f ); Association and association definition: Create Association: 1. Create Association definition. 2. Create associations using world-related methods. Eg: b2fixturedef fixturedef; fixturedef. shape = & dynamicbox; fixturedef. dynsity = 1.0f; fixturedef. friction = 3.0f; // generate the association b2fixture * fixture = body-> createfixtrue (& fixturedef) according to the association definition ); Link and link definition: A link is used to associate multiple rigid bodies so that they can interact with each other. There are many types of links. You must select the desired type. The same two steps: 1. Define. 2. Create according to the definition. Eg: b2linejointdef jointdef; b2vec2 axis (2.0f, 1.0f); axis. normalize (); jointdef. initialize (ground, body, b2vec2 (0.0f, 8.5f), axis); jointdef. motorspeed = 0.0f; jointdef. maxmotorforce = 100366f; jointdef. enablemotor = true; jointdef. lowertransltaion =-4.0f; jointdef. uppertranslation = 4.0f; jointdef. enablelimit = true; // generate the link b2joint * Joint = m_world-> createjoint (& jointdef) based on the link definition ); This blog is from
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