more document in readme.md

README.md

@@ -138,6 +138,49 @@ PenetrationDepthResult result;
 penetrationDepth(o1, o2,request, result);
 ```
 
+FCL supports broadphase collision/distance between two groups of objects and can avoid the n square complexity. For collision, broadphase algorithm can return all the collision pairs. For distance, it can return the pair with the minimum distance. FCL uses a CollisionManager structure to manage all the objects involving the collision or distance operations.
+```cpp
+// Initialize the collision manager for the first group of objects. 
+// FCL provides various different implementations of CollisionManager.
+// Generally, the DynamicAABBTreeCollisionManager would provide the best performance.
+BroadPhaseCollisionManager* manager1 = new DynamicAABBTreeCollisionManager(); 
+// Initialize the collision manager for the second group of objects.
+BroadPhaseCollisionManager* manager2 = new DynamicAABBTreeCollisionManager();
+// To add objects into the collision manager, using BroadPhaseCollisionManager::registerObject() function to add one object
+std::vector<CollisionObject*> objects1 = ...
+for(std::size_t i = 0; i < objects1.size(); ++i)
+manager1->registerObject(objects1[i]);
+// Another choose is to use BroadPhaseCollisionManager::registerObjects() function to add a set of objects
+std::vector<CollisionObject*> objects2 = ...
+manager2->registerObjects(objects2);
+// In order to collect the information during broadphase, CollisionManager requires two settings: 
+// a) a callback to collision or distance; 
+// b) an intermediate data to store the information generated during the broadphase computation
+// For a), FCL provides the default callbacks for both collision and distance.
+// For b), FCL uses the CollisionData structure for collision and DistanceData structure for distance. CollisionData/DistanceData is just a container including both the CollisionRequest/DistanceRequest and CollisionResult/DistanceResult structures mentioned above.
+CollisionData collision_data;
+DistanceData distance_data;
+// Setup the managers, which is related with initializing the broadphase acceleration structure according to objects input
+manager1->setup();
+manager2->setup();
+// Examples for various queries
+// 1. Collision query between two object groups and get collision numbers
+manager2->collide(manager1, &collision_data, defaultCollisionFunction);
+int n_contact_num = collision_data.result.numContacts(); 
+// 2. Distance query between two object groups and get the minimum distance
+manager2->distance(manager1, &distance_data, defaultDistanceFunction);
+double min_distance = distance_data.result.min_distance;
+// 3. Self collision query for group 1
+manager1->collide(&collision_data, defaultCollisionFunction);
+// 4. Self distance query for group 1
+manager1->distance(&distance_data, defaultDistanceFunction);
+// 5. Collision query between one object in group 1 and the entire group 2
+manager2->collide(objects1[0], &collision_data, defaultCollisionFunction);
+// 6. Distance query between one object in group 1 and the entire group 2
+manager2->distance(objects1[0], &distance_data, defaultDistanceFunction); 
+```
+
+
 For more examples, please refer to the test folder:
 - test_fcl_collision.cpp: provide examples for collision test
 - test_fcl_distance.cpp: provide examples for distance test