How to make an object move (force)

[arkdemon]

Hello everyone. I am new to using Newton Game Dynamics so I do not know how to make an object move. I understood that we had to initialize NewtonBodySetForceAndTorqueCallback and NewtonBodySetTransformCallback. However, it is quite vague and it does not work. So, here is my code:

physics.h

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#include <newton/Newton.h>
#include <core/dg.h>

static NewtonWorld *world;//rp3d::DynamicsWorld *world;

struct MovSet{
    glm::vec3 pos;
    glm::vec3 force;
    float mass;
};

#define GRAVITY -9.81f

static void ApplyTransform(const NewtonBody* body, const dFloat* matrix, int threadIndex)
{
    MovSet *mset = (MovSet *) NewtonBodyGetUserData(body);

    // Get the position from the matrix
    glm::vec3 posit (matrix[12], matrix[13], matrix[14]);

    // set the new position and orientation for this entity
    mset->pos = posit;

    NewtonBodySetCentreOfMass(body, glm::value_ptr(mset->pos));
}


// callback to apply external forces to body
static void ApplyForceAndTorque(const NewtonBody* body, dFloat timestep, int threadIndex)
{
    dFloat Ixx;
    dFloat Iyy;
    dFloat Izz;
    dFloat mass;

    // for this tutorial the only external force in the Gravity
    NewtonBodyGetMassMatrix (body, &mass, &Ixx, &Iyy, &Izz);

    MovSet *mset = (MovSet*) NewtonBodyGetUserData(body);

    glm::vec3 gravity  (0.f, mset->mass * GRAVITY, 0.f);

    mset->force += gravity;
    NewtonBodySetForce(body, glm::value_ptr(mset->force+gravity));
}

class Sphere{
public://private:
    NewtonBody *body;
    float rad;

//public:

    BS(float radius, MovSet mset) : rad(radius){
        NewtonCollision *colli = NewtonCreateBox(world, rad, rad, rad, 0, NULL);
        dgMatrix m = dgMatrix(dgQuaternion(), dgVector(mset.pos.x,mset.pos.y,mset.pos.z,1.f));
        body = NewtonCreateDynamicBody(world, colli, &m[0][0]);
        NewtonBodySetMassProperties(body, mset.mass, colli);
        NewtonBodySetCentreOfMass(body, glm::value_ptr(mset.pos));
        NewtonDestroyCollision(colli);

        // save the entity as the user data for this body
        NewtonBodySetUserData (body,&mset);

        NewtonBodySetFreezeState(body,0);
        NewtonBodySetForceAndTorqueCallback(body, ApplyForceAndTorque); // register the apply force and torque callback
        NewtonBodySetTransformCallback(body, ApplyTransform); // register the transformation callback
    }
    ~BS(){
        NewtonDestroyBody(body);
        body = 0;
    }

    float* transform() {
        float matrix[16];
        NewtonBodyGetMatrix(body, matrix);

        return matrix;
    }

    glm::vec3 center(){
        float p[3];
        NewtonBodyGetCentreOfMass(body, p);
        return glm::make_vec3(p);
    }

    glm::vec3 set_center(float *p){
        NewtonBodySetCentreOfMass(body, p);
    }

    MovSet *mset(){
        return (MovSet *)NewtonBodyGetUserData(body);
    }
};
#endif // PHYSICS_H

In my scene class, in my function update, I use

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NewtonUpdate(world, 1.f/60.f);

Here is how I init the NewtonWorld

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    world = NewtonCreate();

    // configure the Newton world to use iterative solve mode 0
    // this is the most efficient but the less accurate mode
    NewtonSetSolverModel (world, 5);
    // for deterministic behavior call this function each time you change the world
    NewtonInvalidateCache (world);

Thank you for your help.

[Julio Jerez]

look at this tutorial
..\newton-dynamics\applications\tutorialsSDK300\NewtonTutorials

[arkdemon]

Hello, thank you for your answer.
I made it work: here is the code:

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static NewtonWorld *world;

struct MovSet{
    glm::vec3 pos,rot;
    glm::vec3 force, torque;
    glm::mat4 model;
    float mass;
};


#define GRAVITY -9.81f

static void ApplyTransform(const NewtonBody* body, const dFloat* matrix, int threadIndex)
{
    MovSet *mset = (MovSet*) NewtonBodyGetUserData(body);
    glm::vec3 p = glm::vec3(matrix[12], matrix[13], matrix[14]);
    mset->pos = p;
    mset->model = glm::make_mat4(matrix);
}


// callback to apply external forces to body
static void ApplyForceAndTorque(const NewtonBody* body, dFloat timestep, int threadIndex)
{
    /*dFloat Ixx;
    dFloat Iyy;
    dFloat Izz;
    dFloat mass;

    // for this tutorial the only external force in the Gravity
    NewtonBodyGetMassMatrix (body, &mass, &Ixx, &Iyy, &Izz);*/

    MovSet *mset = (MovSet*) NewtonBodyGetUserData(body);

    glm::vec3 gravity  (0.f, mset->mass * GRAVITY, 0.f);

    mset->force += gravity;
    NewtonBodySetForce(body, glm::value_ptr(mset->force));
    mset->force = glm::vec3(0.f);
}

class BS{
public:
    NewtonBody *body;
    float rad;

    BS(float radius, MovSet &mset) : rad(radius){
        NewtonCollision *colli = NewtonCreateBox(world, rad, rad, rad, 0, NULL);
        dgMatrix m = dgMatrix(dgQuaternion(), dgVector(mset.pos.x,mset.pos.y,mset.pos.z,1.f));
        body = NewtonCreateDynamicBody(world, colli, &m[0][0]);
        NewtonBodySetMassProperties(body, mset.mass, colli);
        NewtonBodySetCentreOfMass(body, glm::value_ptr(mset.pos));
        NewtonBodySetForce(body, glm::value_ptr(mset.force));

        mset.model = glm::translate(glm::mat4(1.f), mset.pos);
        NewtonBodySetMatrix(body, glm::value_ptr(mset.model));
        NewtonDestroyCollision(colli);

        // save the entity as the user data for this body
        NewtonBodySetUserData (body,&mset);

        NewtonBodySetFreezeState(body,0);
        NewtonBodySetSleepState(body, 0);
        NewtonBodySetForceAndTorqueCallback(body, ApplyForceAndTorque); // register the apply force and torque callback
        NewtonBodySetTransformCallback(body, ApplyTransform); // register the transformation callback
    }
    ~BS(){
        NewtonDestroyBody(body);
        body = 0;
    }

    float* transform() {
        float matrix[16];
        NewtonBodyGetMatrix(body, matrix);

        return matrix;
    }

    glm::vec3 center(){
        float p[3];
        NewtonBodyGetCentreOfMass(body, p);
        return glm::make_vec3(p);
    }

    glm::vec3 set_center(float *p){
        NewtonBodySetCentreOfMass(body, p);
    }

    MovSet *mset(){
        return (MovSet *)NewtonBodyGetUserData(body);
    }
};

I found out that it is REALLY IMPORTANT to send the REFERENCE for NewtonBodySetUserData

[Julio Jerez]

maybe you will better using the CNetwon

../newton-dynamics\applications\tutorialsSDK300\CNewtonTutorials

it is much small set of file, and eassy to get going in C++.
It already has calles that handle user data, ray case, and lot of other things.

[arkdemon]

Ok thank you very much.