Unity Plugin: Accessing contact and collision data

[makeplayhappy]

Are there any available collision callbacks?
I'm wondering what the best way to be informed about when collisions are happening.
Currently I'm doing this:

if( Data != null && Data->contact != null && Data->ncon > 0 ){  
      MujocoLib.mjContact_* contact = Data->contact;  
      for(int i = 0; i < Data->ncon; i++){  
        // match up contact->geom1 contact->geom2 with _orderedComponents[].MujocoId and trigger a collision callback / event
        contact++;
      }  
 }  

I imagine I'm missing something but I can't find anything in the code or docs that suggest any other way.

[erez-tom]

If you want to know when whether a specific geom is touching anything, you can create a site that envelopes it, assign a touch sensor to the site, and read the sensor value (which, in this case, will be the normal force).

If you want the list of geoms in contact with a certain geom, you would indeed have to scan the list of Data->contact to find that out.

Invoking collision detection manually is possible in principle (this is where the specific collision callbacks reside, and here there's some explanation how it works). Particularly, if you want to know whether a specific pair of geoms is in contact, the MuJoCo Way would be to define a pair and force collision detection on this pair at every timestep. However:

• we haven't yet created a component for pair.
• You'd still have to scan the list of contacts to find out their relative distance -- the pair object won't give you direct access to the relevant contacts (an interesting feature request -- I will add it to our list).

See also #123.

Does this explanation cover your intended use-case?

[makeplayhappy]

Ah, touch sensor is what I was looking for and should be enough for my use case, thanks.