| 1 | Breakable Joints |
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| 2 | |
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| 3 | ================================================================================ |
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| 4 | |
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| 5 | Description: |
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| 6 | This is a small addition to ODE that makes joints breakable. Breakable means |
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| 7 | that if a force on a joint is to high it wil break. I have included a modified |
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| 8 | version of test_buggy.cpp (test_breakable.cpp) so you can see it for your self. |
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| 9 | Just drive your buggy into an obstacle and enjoy! |
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| 10 | |
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| 11 | ================================================================================ |
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| 12 | |
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| 13 | Installation instructions: |
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| 14 | - copy joint.h, joint.cpp, ode.cpp and step.cpp to the ode/src/ directory |
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| 15 | - copy common.h and object.h to the include/ directory |
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| 16 | - copy test_breakable.cpp to the ode/test/ directory |
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| 17 | - add test_breakable.cpp to the ODE_TEST_SRC_CPP object in the makefile. |
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| 18 | - make ode-lib |
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| 19 | - make ode-test |
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| 20 | You can also use the diffs. The above files will quickly go out of sync with the |
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| 21 | rest of ODE but the diffs wil remain valid longer. |
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| 22 | |
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| 23 | ================================================================================ |
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| 24 | |
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| 25 | Functions: |
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| 26 | dJointSetBreakable (dJointID joint, int b) |
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| 27 | If b is 1 the joint is made breakable. If b is 0 the joint is made |
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| 28 | unbreakable. |
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| 29 | |
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| 30 | void dJointSetBreakCallback (dJointID joint, dJointBreakCallback *callbackFunc) |
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| 31 | Sets the callback function for this joint. If a funtion is set it will be |
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| 32 | called if the joint is broken but before it is actually detached or deleted. |
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| 33 | |
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| 34 | void dJointSetBreakMode (dJointID joint, int mode) |
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| 35 | Use this functions to set some flags. These flags can be ORred ( | ) |
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| 36 | together; ie. dJointSetBreakMode (someJoint, |
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| 37 | dJOINT_BREAK_AT_B1_FORCE|dJOINT_DELETE_ON_BREAK) |
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| 38 | dJOINT_DELETE_ON_BREAK - If the joint breaks it wil be deleted. |
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| 39 | dJOINT_BREAK_AT_B1_FORCE - If the force on body 1 is to high the joint will |
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| 40 | break |
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| 41 | dJOINT_BREAK_AT_B1_TORQUE - If the torque on body 1 is to high the joint will |
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| 42 | break |
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| 43 | dJOINT_BREAK_AT_B2_FORCE - If the force on body 2 is to high the joint will |
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| 44 | break |
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| 45 | dJOINT_BREAK_AT_B2_TORQUE - If the torque on body 2 is to high the joint will |
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| 46 | break |
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| 47 | |
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| 48 | void dJointSetBreakForce (dJointID joint, int body, dReal x, dReal y, dReal z) |
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| 49 | With this function you can set the maximum force for a body connected to this |
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| 50 | joint. A value of 0 for body means body 1, 1 means body 2. The force is |
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| 51 | relative to the bodies rotation. |
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| 52 | |
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| 53 | void dJointSetBreakTorque (dJointID joint, int body, dReal x, dReal y, dReal z) |
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| 54 | With this function you can set the maximum torque for a body connected to this |
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| 55 | joint. A value of 0 for body means body 1, 1 means body 2. The torque is |
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| 56 | relative to the bodies rotation. |
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| 57 | |
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| 58 | int dJointIsBreakable (dJointID joint) |
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| 59 | Returns 1 if this joint is breakable, 0 otherwise. |
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| 60 | |
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| 61 | int dJointGetBreakMode (dJointID joint) |
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| 62 | Returns the breakmode flag. |
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| 63 | |
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| 64 | void dJointGetBreakForce (dJointID joint, int body, dReal *force) |
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| 65 | Returns the force at what this joint will break. A value of 0 for body means |
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| 66 | body 1, 1 means body 2. force must have enough space for 3 dReal values. |
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| 67 | |
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| 68 | void dJointGetBreakTorque (dJointID joint, int body, dReal *torque) |
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| 69 | Returns the torque at what this joint will break. A value of 0 for body |
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| 70 | means body 1, 1 means body 2. force must have enough space for 3 dReal |
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| 71 | values. |
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| 72 | |
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| 73 | ================================================================================ |
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| 74 | |
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| 75 | The callback function is defined like this (in common.h): |
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| 76 | void dJointBreakCallback (dJointID); |
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| 77 | |
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| 78 | ================================================================================ |
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| 79 | |
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| 80 | Problems, known bugs & other issues: |
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| 81 | - If the timestep is very small then joints get a lot weaker. They can even fall |
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| 82 | apart! |
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| 83 | - I have tested all this with the latest checkout from CVS (at the time of |
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| 84 | writing ofcourse). I haven't tested it with earlier versions of ODE. |
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| 85 | - I have modified the code that fills the jointfeedback struct. I haven't tested |
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| 86 | if it still works. |
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| 87 | - I'm not sure if the forces are really relative to the connected bodies. |
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| 88 | - There are some memory leaks in the test_breakable.cpp example. |
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| 89 | |
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| 90 | ================================================================================ |
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| 91 | |
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| 92 | Bugfixes and changes: |
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| 93 | 09/08/2003 |
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| 94 | - I fixed a bug when there where 0 joints in the simulation |
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| 95 | |
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| 96 | 06/12/2003 |
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| 97 | - dJointGetBreakMode() added, by vadim_mcagon@hotmail.com |
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| 98 | |
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| 99 | 11/03/2004 |
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| 100 | - Updated files to work with latest CVS checkout. |
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| 101 | - Added support for dWorldStepFast1() |
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| 102 | - Added separate test_breakable.cpp example. |
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| 103 | - Updated the code that breaks and destroys a joint. |
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| 104 | |
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| 105 | ================================================================================ |
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| 106 | |
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| 107 | Send me an e-mail if you have any suggestions, ideas, bugs, bug-fixes, anything! |
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| 108 | e-mail: roelvandijk@home.nl |
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| 109 | |
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| 110 | Roel van Dijk - 11/03/2004 |
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