How to use the Function of mjv_applyPerturbForce()?

[BowenFF]

Intro

Hi!

I am a undergraduate at RWTH Aachen University, I use MuJoCo for my research on manipulator and external force.

My setup

Mujoco 3.2.5, C++, Ubuntu

My question

I am confused that how to use the API "void mjv_applyPerturbForce(const mjModel* m, mjData* d, const mjvPerturb* pert);
";
As the document says "Set perturb force,torque in d->xfrc_applied, if selected body is dynamic.";
When I check the struct of mjvPerturb, it doesn't contain the information of force or torque? How can I apply the external force?

I have tried another API "mj_applyFT()", it works well. But I have no idea to visualize the external force which it produce, can you tell me the way to visualize the external force?

Minimal model and/or code that explain my question

struct mjvPerturb_ { // object selection and perturbation
int select; // selected body id; non-positive: none
int flexselect; // selected flex id; negative: none
int skinselect; // selected skin id; negative: none
int active; // perturbation bitmask (mjtPertBit)
int active2; // secondary perturbation bitmask (mjtPertBit)
mjtNum refpos[3]; // reference position for selected object
mjtNum refquat[4]; // reference orientation for selected object
mjtNum refselpos[3]; // reference position for selection point
mjtNum localpos[3]; // selection point in object coordinates
mjtNum localmass; // spatial inertia at selection point
mjtNum scale; // relative mouse motion-to-space scaling (set by initPerturb)
};
typedef struct mjvPerturb_ mjvPerturb;

Confirmations

• I searched the latest documentation thoroughly before posting.
• I searched previous Issues and Discussions, I am certain this has not been raised before.

[yuvaltassa]

Read the simulate code to understand how perturbations work.

Forces in xfrc_applied can be visualized with mjVIS_PERTFORCE