Real-Time Physics Simulation Forum

Re: RayTest fails

2021-07-29T17:52:00+00:00

Thank you very much for your support. I was able to solve my problem this way :

Code:

btCollisionWorld::ClosestRayResultCallback rayCallback(rayFrom, rayTo);rayCallback.m_collisionFilterGroup = 0b1111111;rayCallback.m_collisionFilterMask = 0b1111111;mpDynamicsWorld->rayTest(rayFrom, rayTo, rayCallback);

In case it helps someone...

Statistics: Posted by paokakis — Thu Jul 29, 2021 5:52 pm

Re: RayTest fails

2021-07-29T16:55:15+00:00

Check out the ctor implementation of RayResultCallback, from which ClosestRayHitCallback derives:

Code:

                RayResultCallback()                        : m_closestHitFraction(btScalar(1.)),                          m_collisionObject(0),                          m_collisionFilterGroup(btBroadphaseProxy::DefaultFilter),                          m_collisionFilterMask(btBroadphaseProxy::AllFilter),                          //@BP Mod                          m_flags(0)                {                         }

You can see the default group and mask being set. If you track down where btBroadphaseProxy::DefaultFilter and btBroadphaseProxy::AllFilter are defined you'll learn their values are 1 and -1 respectively (of course, interpreted as unsigned). You can set those data members to whatever you want after instantiation: they are public because RayResultCallback is a C++ struct, which is just a class but with all methods and members defaulting to public.

Statistics: Posted by drleviathan — Thu Jul 29, 2021 4:55 pm

Re: RayTest fails

2021-07-29T11:25:46+00:00

I used also other groups but no success... I tried for example group 4 with mask 4 but again I get no raytest results. Only when I use group 1 with mask 1 it works, ah also the default works (no groups and no mask specified).

You need to set your callback's group to some single bit and then be sure set that same bit in the mask of all objects which should be pickable by rays.

How can I set my callback's group to something different?

Statistics: Posted by paokakis — Thu Jul 29, 2021 11:25 am

Re: RayTest fails

2021-07-28T20:22:02+00:00

The collision groups and masks are used at the BroadPhase to submit overlap pairs to the NarrowPhase.

AABB's overlaps in the BroadPhase are submitted to the NarrowPhase iff each object collides with the other's group. In other words when: ObjectA.group & ObjectB.mask && ObjectB.group & ObjectA.mask.

If you don't submit a custom mask when adding an object to the world it receives a default value of btBroadphaseProxy::AllFilter whose value is -1 in unsigned context: e.g. all bits set.

When you use a zero mask then it collides with nothing, including ray traces...

... because btCollisionWorld::ClosestRayResultCallback derives from btCollisonWorld::RayResultCallback which has m_collisionFilterGroup and m_collisionFilterMask data members which default to btBroadphaseProxy::AllFilter and are used when checking for overlaps in the BroadPhase data structure.

You need to set your callback's group to some single bit and then be sure set that same bit in the mask of all objects which should be pickable by rays.

Statistics: Posted by drleviathan — Wed Jul 28, 2021 8:22 pm

RayTest fails

2021-07-28T15:45:43+00:00

Hello to the group,

I am using bullet in an OpenGL application creating a 3D space shooter. At some point I want to ray cast from the middle of the screen to a rigid body on the screen. This works fine for rigid bodies with group 1 and mask 1. But I have some objects that don't collide with others set a group of 1 and mask of 0. On those objects the the ray misses. Here is the ray that I am casting :

Code:

bool BphysicsManager::rayHasHit(glm::vec3& rayFromWorld, glm::vec3& rayToWorld, btVector3* hitPointWorld, btRigidBody** body){mMutex->lock();bool ret;rayFrom.setX(rayFromWorld.x);rayFrom.setY(rayFromWorld.y);rayFrom.setZ(rayFromWorld.z);rayTo.setX(rayToWorld.x);rayTo.setY(rayToWorld.y);rayTo.setZ(rayToWorld.z);btCollisionWorld::ClosestRayResultCallback rayCallback(rayFrom, rayTo);mpDynamicsWorld->rayTest(rayFrom, rayTo, rayCallback);if (rayCallback.m_collisionObject){*body = (btRigidBody*)btRigidBody::upcast(rayCallback.m_collisionObject);*hitPointWorld = rayCallback.m_hitPointWorld;auto colShape = (*body)->getCollisionShape();if (dynamic_cast(colShape) != nullptr){*body = nullptr;}}ret = rayCallback.hasHit();mMutex->unlock();return ret;}

and here is the rigid body creation :

Code:

btRigidBody* BphysicsManager::loadBody(btVector3& pLocation, float pSizeX, float pSizeY, float pSizeZ, btVector3& scale , float pDensity, void* userPtr, shape_type_t type, int group, int mask){mMutex->lock();btCollisionShape* shape;switch (type) {case SHAPE_BOX:shape = new btBoxShape(btVector3(pSizeX, pSizeY, pSizeZ));break;case SHAPE_SPHERE:shape = new btSphereShape(pSizeX / 2);break;case SHAPE_CAPSULE:shape = new btCapsuleShape(pSizeY, pSizeY / 4);break;case SHAPE_CYLINDER:shape = new btCylinderShape(btVector3(pSizeX / 2, pSizeY / 2, pSizeZ / 2));break;default:shape = new btSphereShape(pSizeX / 2);break;}shape->setMargin(0.001f);shape->setLocalScaling(scale);btTransform startTransform = btTransform();startTransform.setIdentity();startTransform.setOrigin(pLocation);//put it to x,y,z coordinatesbtAssert((!shape || shape->getShapeType() != INVALID_SHAPE_PROXYTYPE));//rigidbody is dynamic if and only if mass is non zero, otherwise staticbool isDynamic = (pDensity != 0.f);btVector3 localInertia(0, 0, 0);if (isDynamic)shape->calculateLocalInertia(pDensity, localInertia);//using motionstate is recommended, it provides interpolation capabilities, and only synchronizes 'active' objects#define USE_MOTIONSTATE 1#ifdef USE_MOTIONSTATEbtDefaultMotionState* myMotionState = new btDefaultMotionState(startTransform);vMotionStates.push_back(myMotionState);btRigidBody::btRigidBodyConstructionInfo cInfo(pDensity, myMotionState, shape, localInertia);btRigidBody* body = new btRigidBody(cInfo);body->setWorldTransform(startTransform);#elsebtRigidBody* body = new btRigidBody(mass, 0, shape, localInertia);body->setWorldTransform(startTransform);#endif//if (userPtr) body->setUserPointer(userPtr);vCollisionShapes.push_back(shape);vRigidBodies.push_back(body);body->setAngularFactor(1.f);body->setLinearVelocity(btVector3(0, 0, 0));body->setAngularVelocity(btVector3(0, 0, 0));body->setFriction(1.0);body->activate(true);body->setSleepingThresholds(0.f, 0.f);if (userPtr) body->setUserPointer(userPtr);mpDynamicsWorld->addRigidBody(body, group, mask);mMutex->unlock();return body;}

Can someone identify some problem?

Statistics: Posted by paokakis — Wed Jul 28, 2021 3:45 pm