Box2D Manually Move Body

Box2D Manually Move Body

ENTER SITE »»» DOWNLOAD PDF
CLICK HERE »»» BOOK READER

File Name:Box2D Manually Move Body.pdf
Size: 3553 KB
Type: PDF, ePub, eBook

Category: Book
Uploaded: 26 May 2019, 16:24 PM
Rating: 4.6/5 from 718 votes.

Status: AVAILABLE

Last checked: 17 Minutes ago!

In order to read or download Box2D Manually Move Body ebook, you need to create a FREE account.

Download Now!

eBook includes PDF, ePub and Kindle version

✔ Register a free 1 month Trial Account.

✔ Download as many books as you like (Personal use)

✔ Cancel the membership at any time if not satisfied.

✔ Join Over 80000 Happy Readers

Box2D Manually Move BodyWhat I want is for when the body leaves the edge of the screen, to come back from that current point back to its original point instantaneously. How do I do this? For example using setTransform disabled my ContactFilter in random moments, which cost me several days of debugging until I found that. What I want is for this to occur forever with the asteroid moving across the screen and then being put back in its original spot to move across again. It might be inactive and will therefore not be processed at the new position! java body.setTransform(targetTeleportPosition, body.angle); body.setAwake(true); It might be inactive and will therefore not be processed at the new position! java body.setTransform(targetTeleportPosition, body.angle); body.setAwake(true); It might be currently inactive and without waking it up neither gravity nor any immediate collisions will affect it at the new position. Please be sure to answer the question. Provide details and share your research. Making statements based on opinion; back them up with references or personal experience. To learn more, see our tips on writing great answers. Browse other questions tagged android libgdx box2d or ask your own question. It only takes a minute to sign up. That is, the nature of bodies in box2d. You make a dynamic body, and apply impulse or force to it in the direction you want it to move. This object can be moved with a touch, and once placed i a suitable location that object should be permanent there. Sorry im still new to game programming. I'd recommend making a simple (static) box. Also, don't forget to set the 'restitution' for the ball and box. They only move how you tell them to, so they aren't affected by collisions or other forces (like gravity). Check out this thread for a good discussion about this.Please be sure to answer the question. Use MathJax to format equations. MathJax reference. To learn more, see our tips on writing great answers.https://deconsystems.com/userfiles/braun-lifts-manuals.xml

Tags:
• box2d manually move body, box2d manually move body fat, box2d manually move body parts, box2d manually move body song.

Browse other questions tagged box2d cocos2d-iphone or ask your own question. Some of the download links are missing.Feb 21: Added RUBE sample loader for Cocos2d-X v3.4. Feb 17: Funny Fists released in iOS App store and Google Play store. ( YouTube video ) Sep 18: Added RUBE sample loader for Cocos2d-X. Aug 12: RUBE loader for Nape by Zeh Fernando Aug 7: Added RUBE sample loader for SFML. Jul 30: Try my MiniLD 7dRTS entry. Jul 24: Added physics-driven particles tutorial. Jul 20: New blog post: rendering solid ground (as in Downhill Supreme) May 22: Downhill Supreme is out now! (iOS) Mar 10: RUBE loader for libGDX by Tim Scott Jan 28: New blog post: a functional combustion engine. Jan 22: New blog post: wind tunnel Jan 20: Added explosions tutorial. Jan 16: Added buoyancy tutorial. Jan 16: AndEngine sample project to load RUBE scene by Bart Hirst Nov 23: A sample project to load R.U.B.E scenes into Chipmunk physics. Details here. Nov 14: An XCode sample project to load R.U.B.E scenes on iOS is now available. Details here. Nov 11: A Java version of b2dJson is now available, based on JBox2D. Nov 6: A Javascript version of b2dJson based on box2dweb is now available. Demo here! Nov 2: The full specification of the JSON format used by b2dJson can be found here: b2dJson file structure Oct 28: YouTube video: 2-minute ragdoll in R.U.B.E Box2D editor Sep 29: YouTube video: R.U.B.E Box2D editor usage example This could be a player characterDepending on the game, sometimes a body should gain speed gradually,It is very tempting to use the.http://ghespanail.com/fckeditor_userfiles/braun-lift-repair-manual.xml SetLinearVelocity function to explicitly set the velocity for a body to accomplish this, and indeed itWhile it often looks fine on the screen,We'll look at two situations, one where the body should immediately start moving at the desired speed, and oneTo start with we'll needThis fence will come inTo keep track of what the user wants to do, we'll have a class variableSetting velocity directly For many applications this mayInside the Step() function, we will take whatever action is required each time step:Trying this code in the testbed you'll see that this setup gives us the instantaneousWhen coming to a stop the speed is reduced to 98 of the previous frame's speed,For this example we have a pretty basic logic which simply applies the maximum force in everyYou will likely want to adjust this for the applicationFor this you could just look at the difference between theRemembering from the previous topic that forces act gradually, it might seem unlikely that we couldHowever, if we make the time span very short andFirst we need to do a little math.To get an instantaneousNow we know everything except f, so we do something like this:However sinceTry changing the 'https' in the page URL to just 'http' Click here: Contact gmail 'iforce2d' If you find this site useful please consider supporting it:). The Dynamics module sits on top of the Common and Collision modules, so you should be somewhat familiar with those by now. In the following, you may see some references to classes that have not been described yet. Therefore, you may want to quickly skim this chapter before reading it closely. You can apply forces, torques, and impulses to bodies. Bodies can be static, kinematic, or dynamic. Here are the body type definitions: Internally, Box2D stores zero for the mass and the inverse mass. Static bodies can be moved manually by the user. A static body has zero velocity. Static bodies do not collide with other static or kinematic bodies.http://schlammatlas.de/en/node/15477 Kinematic bodies do not respond to forces. They can be moved manually by the user, but normally a kinematic body is moved by setting its velocity. A kinematic body behaves as if it has infinite mass, however, Box2D stores zero for the mass and the inverse mass. Kinematic bodies do not collide with other kinematic or static bodies. They can be moved manually by the user, but normally they move according to forces. A dynamic body can collide with all body types. A dynamic body always has finite, non-zero mass. If you try to set the mass of a dynamic body to zero, it will automatically acquire a mass of one kilogram and it won't rotate. Bodies carry fixtures and move them around in the world. Bodies are always rigid bodies in Box2D. That means that two fixtures attached to the same rigid body never move relative to each other and fixtures attached to the same body don't collide. Normally, bodies acquire their mass properties from the fixtures. However, you can override the mass properties after a body is constructed. This way you can query the body positions to update the positions of your graphical entities. You should also keep body pointers so you can destroy them when you are done with them. The body definition holds the data needed to create and initialize a body. This means you can recycle a body definition to create multiple bodies. You should establish the body type at creation because changing the body type later is expensive. This has far better performance than creating the body at the world origin and then moving the body. If you create several bodies at the origin, then performance will suffer. The first point is the body's origin. Fixtures and joints are attached relative to the body's origin. The second point of interest is the center of mass. The center of mass is determined from mass distribution of the attached shapes or is explicitly set with b2MassData. Much of Box2D's internal computations use the center of mass position.http://connect-log.com/images/box2d-manual-as3.pdf For example b2Body stores the linear velocity for the center of mass. Therefore you specify the position of the body's origin. You may also specify the body's angle in radians, which is not affected by the position of the center of mass. If you later change the mass properties of the body, then the center of mass may move on the body, but the origin position does not change and the attached shapes and joints do not move. You can define fixtures and joints in that frame. Those fixtures and joint anchors never move in the local frame of the body. Damping is different than friction because friction only occurs with contact. Damping is not a replacement for friction and the two effects should be used together. Normally you will use a damping value between 0 and 0.1. I generally do not use linear damping because it makes bodies look like they are floating. At small damping values the damping effect is mostly independent of the time step. At larger damping values, the damping effect will vary with the time step. This is not an issue if you use a fixed time step (recommended). Be careful though, increased gravity can decrease stability. Well it is expensive to simulate bodies, so the less we have to simulate the better. When a body comes to rest we would like to stop simulating it. If a body is awake and collides with a sleeping body, then the sleeping body wakes up. Bodies will also wake up if a joint or contact attached to them is destroyed. You can also wake a body manually. Such a body should not rotate, even under load. You can use the fixed rotation setting to achieve this: This is called discrete simulation. In discrete simulation, rigid bodies can move by a large amount in one time step. If a physics engine doesn't account for the large motion, you may see some objects incorrectly pass through each other. This effect is called tunneling. This is done by sweeping shapes from their old position to their new positions.https://evocative.ru/wp-content/plugins/formcraft/file-upload/server/content/files/1627eb0b6bff6d---brother-p-touch-pt-1230pc-manual.pdf The engine looks for new collisions during the sweep and computes the time of impact (TOI) for these collisions. Bodies are moved to their first TOI and then the solver performs a sub-step to complete the full time step. There may be additional TOI events within a sub-step. This is done to keep performance reasonable. In some game scenarios you need dynamic bodies to use CCD. For example, you may want to shoot a high speed bullet at a stack of dynamic bricks. Without CCD, the bullet might tunnel through the bricks. Bullets will perform CCD with both static and dynamic bodies. You should decide what bodies should be bullets based on your game design. If you decide a body should be treated as a bullet, use the following setting. This state is similar to sleeping except the body will not be woken by other bodies and the body's fixtures will not be placed in the broad-phase. This means the body will not participate in collisions, ray casts, etc. These joints will not be simulated. You should be careful when you activate a body that its joints are not distorted. So you should not use activation for streaming worlds.This gives you a hook to link your application objects to bodies. You should be consistent to use the same object type for all body user data. This lets the world create the body with an efficient allocator and add the body to the world data structure. The world won't know about the body and the body won't be properly initialized. So you can create temporary body definitions and reuse the same body definitions. However, you should be mindful to nullify body pointers that you keep in your game engine. This has important implications for how you manage shape and joint pointers. These include setting mass properties, accessing position and velocity, applying forces, and transforming points and vectors. For static bodies, the mass and rotational inertia are set to zero. When a body has fixed rotation, its rotational inertia is zero.www.dantizuma.com/files/files/canon-mf5630-service-manual.pdf You can also adjust the mass of a body at run-time. This is usually done when you have special game scenarios that require altering the mass. You can do this with: You can access this state data efficiently through the following functions: This is common when rendering your associated game actor. You can also set the position, although this is less common since you will normally use Box2D to simulate movement. Much of the internal simulation in Box2D uses the center of mass. However, you should normally not need to access it. Instead you will usually work with the body transform. For example, you may have a body that is square. The body origin might be a corner of the square, while the center of mass is located at the center of the square. The linear velocity is for the center of mass. Therefore, the linear velocity may change if the mass properties change. When you apply a force or an impulse, you provide a world point where the load is applied. This often results in a torque about the center of mass. Sometimes this is undesirable. For example, you may be applying a steady force and want to allow the body to sleep to improve performance. In this case you can use the following code. These functions are efficient (when inlined). This is mainly useful if you need to access the fixture's user data. You can use this to get information about the current contacts. Be careful, because the contact list may not contain all the contacts that existed during the previous time step. Therefore Box2D provides the b2Fixture class to attach shapes to bodies. A body may have zero or more fixtures. A body with multiple fixtures is sometimes called a compound body. You do not need to store the fixture pointer since the fixture will automatically be destroyed when the parent body is destroyed. You can create multiple fixtures on a single body. You may do this to model a breakable object.https://www.birdandwildlifeteam.com/wp-content/plugins/formcraft/file-upload/server/content/files/1627eb0c4c6c36---brother-p-touch-manual.pdf Otherwise you can just leave the fixture alone and let the body destruction take care of destroying the attached fixtures. The density can be zero or positive. You should generally use similar densities for all your fixtures. This will improve stacking stability. You must call ResetMassData for this to occur. Box2D supports static and dynamic friction, but uses the same parameter for both. Friction is simulated accurately in Box2D and the friction strength is proportional to the normal force (this is called Coulomb friction). The friction parameter is usually set between 0 and 1, but can be any non-negative value. A friction value of 0 turns off friction and a value of 1 makes the friction strong. When the friction force is computed between two shapes, Box2D must combine the friction parameters of the two parent fixtures. This is done with the geometric mean: This is usually done in the b2ContactListener callback. The restitution value is usually set to be between 0 and 1. Consider dropping a ball on a table. A value of zero means the ball won't bounce. This is called an inelastic collision. A value of one means the ball's velocity will be exactly reflected. This is called a perfectly elastic collision. Restitution is combined using the following formula. This is usually done in the b2ContactListener callback. This is because Box2D uses an iterative solver. Box2D also uses inelastic collisions when the collision velocity is small. This is done to prevent jitter.For example, say you make a character that rides a bicycle. You want the bicycle to collide with the terrain and the character to collide with the terrain, but you don't want the character to collide with the bicycle (because they must overlap). Box2D supports such collision filtering using categories and groups. For each fixture you can specify which category it belongs to. You also specify what other categories this fixture can collide with.https://exactblue.com/wp-content/plugins/formcraft/file-upload/server/content/files/1627eb0d425971---brother-p-touch-pt-1700-manual.pdf For example, you could specify in a multiplayer game that all players don't collide with each other and monsters don't collide with each other, but players and monsters should collide. This is done with masking bits. For example: You can have all fixtures with the same group index always collide (positive index) or never collide (negative index). Group indices are usually used for things that are somehow related, like the parts of a bicycle. In the following example, fixture1 and fixture2 always collide, but fixture3 and fixture4 never collide. In other words, group filtering has higher precedence than category filtering. Here is a list: You can get and set the b2Filter structure on an existing fixture using b2Fixture::GetFilterData and b2Fixture::SetFilterData. Note that changing the filter data will not add or remove contacts until the next time step (see the World class). This is done by using sensors. A sensor is a fixture that detects collision but does not produce a response. Sensors may be static, kinematic, or dynamic. Remember that you may have multiple fixtures per body and you can have any mix of sensors and solid fixtures. Also, sensors only form contacts when at least one body is dynamic, so you will not get a contact for kinematic versus kinematic, kinematic versus static, or static versus static. There are two ways to get the state of a sensor: Typical examples in games include ragdolls, teeters, and pulleys. Joints can be combined in many different ways to create interesting motions. You can use motors to control position by specifying a joint velocity that is proportional to the difference between the actual and desired position. Then the motor will attempt to keep the joint from moving until the load becomes too strong. All joints are connected between two different bodies. One body may static.This is actually the default behavior and you must set the collideConnected Boolean to allow collision between to connected bodies.damabilisim.com/images_upload/files/canon-mf5550-user-manual.pdf Often a joint will be defined by anchor points. These are points fixed in the attached bodies. Box2D requires these points to be specified in local coordinates. This way the joint can be specified even when the current body transforms violate the joint constraint --- a common occurrence when a game is saved and reloaded. Additionally, some joint definitions need to know the default relative angle between the bodies. This is necessary to constrain rotation correctly. However, these initialization functions should usually only be used for prototyping. Production code should define the geometry directly. This will make joint behavior more robust. We cover these now. This brings up an old issue: You must create and destroy bodies and joints using the create and destroy methods of the b2World class. This will make the program crash in a controlled manner if you try to reuse the pointer. Heed this warning well: You may organize your game engine so that joints are always destroyed before the attached bodies. In this case you don't need to implement the listener class. See the section on Implicit Destruction for details. However, there is a lot of useful data contained in joints that you can use to create a rich simulation. This the reaction force applied to body 2 at the anchor point. You can use reaction forces to break joints or trigger other game events. These functions may do some computations, so don't call them if you don't need the result. When you specify a distance joint the two bodies should already be in place. Then you specify the two anchor points in world coordinates. The first anchor point is connected to body 1, and the second anchor point is connected to body 2. These points imply the length of the distance constraint. In this case we decide to allow the bodies to collide. See the Web example in the testbed to see how this behaves. It can be non-intuitive setting these values directly since they have units in terms on Newtons. Box2D provides and API to compute these values in terms of frequency and damping ratio.The frequency is specified in Hertz. Typically the frequency should be less than a half the frequency of the time step. So if you are using a 60Hz time step, the frequency of the distance joint should be less than 30Hz. The reason is related to the Nyquist frequency. At 1, the damping is critical (all oscillations should vanish). The revolute joint has a single degree of freedom: the relative rotation of the two bodies. This is called the joint angle. The initialization function assumes that the bodies are already in the correct position. Like all angles in Box2D, the revolute angle is measured in radians. By convention the revolute joint angle is zero when the joint is created using Initialize(), regardless of the current rotation of the two bodies. The limit will apply as much torque as needed to make this happen. The limit range should include zero, otherwise the joint will lurch when the simulation begins. The speed can be negative or positive. A motor can have infinite force, but this is usually not desirable. Recall the eternal question: So you can provide a maximum torque for the joint motor. The joint motor will maintain the specified speed unless the required torque exceeds the specified maximum. When the maximum torque is exceeded, the joint will slow down and can even reverse. Just set the joint speed to zero, and set the maximum torque to some small, but significant value. The motor will try to prevent the joint from rotating, but will yield to a significant load. The motor is setup to simulate joint friction. You can update the joint speed every time step so you can make the joint move back-and-forth like a sine-wave or according to whatever function you want. For example: Otherwise your joint may become unstable. A prismatic joint prevents relative rotation. Therefore, a prismatic joint has a single degree of freedom. Using this analogy provides an example prismatic joint definition with a joint limit and a friction motor: The prismatic joint needs an explicit axis parallel to the screen. This axis is fixed in the two bodies and follows their motion. So be sure zero is between your lower and upper translation limits. Here are the relevant member functions: The pulley connects two bodies to ground and to each other. As one body goes up, the other goes down. The total length of the pulley rope is conserved according to the initial configuration. This causes one side of the pulley to extend faster than the other. At the same time the constraint force is smaller on one side than the other. You can use this to create mechanical leverage. Also the force in the rope attached to body1 will have half the constraint force as the rope attached to body2. The rope on the other side will have zero length. At this point the constraint equations become singular (bad). You should configure collision shapes to prevent this. In principle you can create gears in Box2D by using compound shapes to model gear teeth. This is not very efficient and might be tedious to author. You also have to be careful to line up the gears so the teeth mesh smoothly. Box2D has a simpler method of creating gears: the gear joint. However, in this case the gear ratio can be negative. Also keep in mind that when one joint is a revolute joint (angular) and the other joint is prismatic (translation), and then the gear ratio will have units of length or one over length. The bodies myBodyA and myBodyB are any bodies from the two joints, as long as they are not the same bodies. This creates a fragile situation. What happens if those joints are deleted? You should also delete the gear joint before you delete any of the bodies involved. It attempts to drive a point on a body towards the current position of the cursor. There is no restriction on rotation. The target point initially coincides with the body's anchor point. The maximum force is used to prevent violent reactions when multiple dynamic bodies interact. You can make this as large as you like.Users often want to achieve precise positioning and instantaneous response. The mouse joint doesn't work very well in that context. You may wish to consider using kinematic bodies instead. The wheel joint also provides a suspension spring. See b2WheelJoint.h and Car.h for details. See the Cantilever.h in the testbed to see how the weld joint behaves. However, the Box2D solver is iterative so the joints are a bit soft. So chains of bodies connected by weld joints will flex. When the body breaks, you can destroy a fixture and recreate it on a new body. See the Breakable example in the testbed. This can be useful to prevent chains of bodies from stretching, even under high load.The joint provides 2D translational friction and angular friction.You can set the maximum motor force and torque that will be applied to reach the target position and rotation. If the body is blocked, it will stop and the contact forces will be proportional the maximum motor force and torque.It provides a translation and rotation. The translation has a spring and damper to simulate the vehicle suspension. The rotation allows the wheel to rotate. You can specify an rotational motor to drive the wheel and to apply braking.If the fixture has children, such as a chain shape, then a contact exists for each relevant child. There are different kinds of contacts, derived from b2Contact, for managing contact between different kinds of fixtures. For example there is a contact class for managing polygon-polygon collision and another contact class for managing circle-circle collision. Box2D approximates contact with a small number of points. By convention, the normal points from fixtureA to fixtureB. Separation is negative when shapes overlap. It is possible that future versions of Box2D will create contact points with positive separation, so you may want to check the sign when contact points are reported. Both of these points use the same normal, so they are grouped into a contact manifold, which is an approximation of a continuous region of contact. For convenience, Box2D works with impulses. The normal impulse is just the normal force multiplied by the time step. For convenience, this is stored as an impulse. Box2D uses contact ids to match contact points across time steps. The ids contain geometric features indices that help to distinguish one contact point from another. Sometimes collision filtering will prevent the creation of contacts. Contacts are destroyed with the AABBs cease to overlap. Well, this is correct. We don't know if we need a contact object until one is created to analyze the collision. We could delete the contact right away if the shapes are not touching, or we can just wait until the AABBs stop overlapping. Box2D takes the latter approach because it lets the system cache information to improve performance. Contact objects are not created by the user. However, you are able to access the contact class and interact with it. From those you can get the bodies. This only works inside the b2ContactListener::PreSolve event, discussed below. You can access the contacts directly on the world and body structures. You can also implement a contact listener. These are stored in a graph using a contact edge structure. Use b2ContactListener to get the most accurate results. The contact listener supports several events: begin, end, pre-solve, and post-solve. Instead make a deep copy of the contact point data into your own buffer. The example below shows one way of doing this. Be sure your listener remains in scope while the world object exists. This is called for sensors and non-sensors. This event can only occur inside the time step. This is called for sensors and non-sensors. This may be called when a body is destroyed, so this event can occur outside the time step. This gives you a chance to disable the contact based on the current configuration. For example, you can implement a one-sided platform using this callback and calling b2Contact::SetEnabled(false). The contact will be re-enabled each time through collision processing, so you will need to disable the contact every time-step. The pre-solve event may be fired multiple times per time step per contact due to continuous collision detection. If you don't care about the impulses, you should probably just implement the pre-solve event. For example, you may have a collision that applies damage and try to destroy the associated actor and its rigid body. However, Box2D does not allow you to alter the physics world inside a callback because you might destroy objects that Box2D is currently processing, leading to orphaned pointers. You should always process the contact points immediately after the time step; otherwise some other client code might alter the physics world, invalidating the contact buffer. When you process the contact buffer you can alter the physics world, but you still need to be careful that you don't orphan pointers stored in the contact point buffer. The testbed has example contact point processing that is safe from orphaned pointers. Here is an excerpt. Be sure to read the comments in the listing.For example, you may want to create a door that only certain characters can pass through. This is called contact filtering, because some interactions are filtered out. This class requires you to implement a ShouldCollide function that receives two b2Shape pointers. Your function returns true if the shapes should collide. Make sure your filter stays in scope while the world exists. It manages all aspects of the simulation and allows for asynchronous queries (like AABB queries and ray-casts). Much of your interactions with Box2D will be with a b2World object.