Finding an Object in the Scene

[Shard]

Is there a way to find objects in a scene?

 

For example, I'm trying to locate all the objects (meshes,models) that are within a certain radius of a different model without keeping track of each thing (which is hard to do with Lua scene loading)

[ZioRed]

I haven't tried, but from its description it seems ForEachEntityInAABBDo is useful for this.

[Laurens]

I do this in my tower defense game to find towers within range of each other so they can link.

 

First create a callback function:

 

void _stdcall ForEachEntityInAABBDoCallback(TEntity entity, BP extra)
{
reinterpret_cast<vector<TEntity>*>(extra)->push_back(entity);
}

 

Note that extra contains a vector of TEntity's and the entity that is passed in the callback function is pushed back into this vector.

 

Then, somewhere in your calling code:

 

       TVec3 p = EntityPosition(node->GetEntity());

TVec6 aabb;

aabb.X0 = p.X - node->GetRadius() / 2;
aabb.Y0 = 0;
aabb.Z0 = p.Z - node->GetRadius() / 2;

aabb.X1 = p.X + node->GetRadius() / 2;
aabb.Y1 = 0;
aabb.Z1 = p.Z + node->GetRadius() / 2;

vector<TEntity> *entities = new vector<TEntity>();
ForEachEntityInAABBDo(aabb, reinterpret_cast<byte*>(ForEachEntityInAABBDoCallback), reinterpret_cast<byte*>(entities));

 

entities should now contain all the entities that are in the AABB.

 

Cheers!

[Shard]

I do this in my tower defense game to find towers within range of each other so they can link.

 

First create a callback function:

 

void _stdcall ForEachEntityInAABBDoCallback(TEntity entity, BP extra)
{
reinterpret_cast<vector<TEntity>*>(extra)->push_back(entity);
}

 

Note that extra contains a vector of TEntity's and the entity that is passed in the callback function is pushed back into this vector.

 

Then, somewhere in your calling code:

 

       TVec3 p = EntityPosition(node->GetEntity());

TVec6 aabb;

aabb.X0 = p.X - node->GetRadius() / 2;
aabb.Y0 = 0;
aabb.Z0 = p.Z - node->GetRadius() / 2;

aabb.X1 = p.X + node->GetRadius() / 2;
aabb.Y1 = 0;
aabb.Z1 = p.Z + node->GetRadius() / 2;

vector<TEntity> *entities = new vector<TEntity>();
ForEachEntityInAABBDo(aabb, reinterpret_cast<byte*>(ForEachEntityInAABBDoCallback), reinterpret_cast<byte*>(entities));

 

entities should now contain all the entities that are in the AABB.

 

Cheers!

 

Thanks for that.

While that definitely works, it turns out I actually need different functionality.

 

Instead of a radius, it need it to affect every object on the map and the strength of the effect would be dependent on the distance from the object.

So basically what I need is to be able to iterate through all the objects in a map, do a distance formula and then do the effect.

[Laurens]

Well, there is also ForEachEntityDo that iterates over all objects. You can use the same callback (well, maybe change its name to ForEachEntityDoCallback to avoid confusion) and the same calling code except change this line:

 

ForEachEntityInAABBDo(aabb, reinterpret_cast<byte*>(ForEachEntityInAABBDoCallback), reinterpret_cast<byte*>(entities));

 

in this line:

 

ForEachEntityDo(reinterpret_cast<byte*>(ForEachEntityDoCallback), reinterpret_cast<byte*>(entities));

 

and then simply iterate over entities and do EntityDistance(source, destination).

 

Cheers!

[Shard]

Well, there is also ForEachEntityDo that iterates over all objects. You can use the same callback (well, maybe change its name to ForEachEntityDoCallback to avoid confusion) and the same calling code except change this line:

 

ForEachEntityInAABBDo(aabb, reinterpret_cast<byte*>(ForEachEntityInAABBDoCallback), reinterpret_cast<byte*>(entities));

 

in this line:

 

ForEachEntityDo(reinterpret_cast<byte*>(ForEachEntityDoCallback), reinterpret_cast<byte*>(entities));

 

and then simply iterate over entities and do EntityDistance(source, destination).

 

Cheers!

 

 

Thanks.

Just realized I needed another bit of functionality. I need it to only affect physics bodies >,>

How would I do that?

[Laurens]

There are several ways to go about.

 

You can either set a key and check the key after getting the list of entities or you can specify an entity type in the calling code. I'm not sure how this works but it is on the wiki for the ForEachEntityInAABBDo command. ForEachEntity seems incomplete.

[cocopino]

You could use Entity::GetParent to get the physics body of the entity.

[Canardia]

Gamelib has FindFirstEntityByKey("keyname","value").