Live plotting/ Draw objects in scene

[v-r-a]

I am not able to trace the source code corresponding to the following functionalities in simulate.cc

I am interested in live plotting--
points like the centre of mass (already available in simulate) , the centre of pressure,
desired trajectory,
inertia forces etc
real time in the simulation.

[yuvaltassa]

IIUC you mean that you want to draw 3D objects directly in the scene, correct?
This is possible and easy. Are you using C++ or Python?

[v-r-a]

Yes.
I'm using C++

[yuvaltassa]

In that case you can follow the patterns in engine_vis_visualize.c.

The place to follow down from simulate, btw, is the mjv_updateScene call.

There is a fairly straighforward mjvScene struct, you add geoms to it and they get rendered. Please excuse the abnormally long mjv_addGeoms function... we should break it up 🙂

[v-r-a]

Okay, I'll try this.
Thank you

[v-r-a]

@yuvaltassa, I could render my own centre of mass visual by inserting the following code (copied and adapted from START and FINISH macros used in mjv_addGeom) in basic.cc (also in simulate.cc). I hope this is the intended way.

    // add a decorative geometry
    mjvGeom* mygeom;
    mjtNum sphrad[3] = {0.05,0,0};
    mjtNum sphpos[3] = {0.,0.,0.};
    mjtNum myid3x3[9] = {1,0,0,0,1,0,0,0,1};
    float sphrgba[4] = {0.,0.,0.9,0.8};
    sphpos[0] = d->subtree_com[0];
    sphpos[1] = d->subtree_com[1];
    sphpos[2] = d->subtree_com[2];

    // update scene and render
    mjv_updateScene(m, d, &opt, NULL, &cam, mjCAT_ALL, &scn);
    printf("Number of geometries in the buffer AA: %d\n",scn.ngeom);
    //one more geom to render
    scn.ngeom = scn.ngeom +1;
    // mygeom now points to the last location in geoms buffer
    mygeom = scn.geoms + scn.ngeom -1;
    // decor geom
    mygeom->objtype = mjOBJ_UNKNOWN;
    mygeom->objid = -1;
    mygeom->category = mjCAT_DECOR;
    mygeom->segid = scn.ngeom;  
    mjv_initGeom(mygeom,mjGEOM_SPHERE,sphrad,sphpos,myid3x3,sphrgba);
    printf("Number of geometries in the buffer BB: %d\n",scn.ngeom);
    
    mjr_render(viewport, &scn, &con);