Entity Hit with ammo api

[LIGS]

Hello to all developers!

I’ve been working with PlayCanvas for a while now, and I’m working on a game with a lot of physics. I’m getting to grips with the ammo.js API, which I’m not very familiar with.

Currently, I’m using the convexSweepTest() function, and I can retrieve the position and normal of the hit, but not the hit object itself.

Is it possible to retrieve the entity hit by a sphere or a capsule cast? Is there another function available?

[LeXXik]

The engine will attach the entity to a body it creates, so if the body was created by the engine, you can cast it to Ammo body and you will have access to it. For example:

if (resultCallback.hasHit()) {
    const body = Ammo.castObject(resultCallback.get_m_hitCollisionObject(), Ammo.btRigidBody);
    // body.entity 
}

[LIGS]

Hi LeXXik,

Thank you for taking the time to reply!

With a callback like ClosestRayResultCallback or AllHitsRayResultCallback, yes, it’s possible to retrieve the hit object. But with a callback like ClosestConvexResultCallback, there’s a pointer to the hit object const btCollisionObject* m_hitCollisionObject; but I can’t retrieve the entity from this variable.

[LIGS]

After checking with console.log(), the variable m_hitCollisionObject is not defined. It seems that it’s not possible to retrieve the hit object with convexSweepTest(). I’m going to perform a raycast with the retrieved information, such as the hitPoint and hitNormal.

[LeXXik]

If Ammo.ClosestConvexResultCallback.get_m_hitCollisionObject is undefined, then your Ammo version is too old. Simply get the latest from Ammo:

ammo.js/builds at main · kripken/ammo.js

[LIGS]

Thanks! That was indeed the problem!

However, I imported the Ammo library via the editor, and apparently, it’s not quite the same since it doesn’t contain Ammo.ClosestConvexResultCallback.get_m_hitCollisionObject().

Is it normal for the editor to import an “older” version?

[LeXXik]

The version in Editor is rarely updated, so it is normal that it is some years old. You can safely use the recent one from Ammo repo.