Hi All,

Just a couple questions about how I should approach rendering my client terminals for my game engine I am making.

Here's my current scope:

2D game engine. and I am designing an authoritative server, with a hash-grid where all game objects find themselves in buckets. Clients report their input every frame, and go through a lock-step to get their position from the server, along with their actions.

The clients have access to all of the map data for rendering, but do not have access to of the GameObjects. How should the server communicate which objects to draw?

I want the server to create a list of objects to draw, based on the clients position in the hashgrid, and pass it to the client. Can I pass a list of pointers? or do I have do pass a list of unique object IDs? It seems like passing all the objects over the connection would be pretty heavy on bandwidth.

I realize I may be leaving out some important details, and I'd be happy to try to give more information, but if anyone has any input or reference to documentation, I would appreciate it.

Thanks!

Since all the client handles is user input, rendering and sound output I'd have the server send each client something like this:

struct DrawCall
{
    Vector2 position,
    int Layer,
    uint SpriteID
}

The renderer in the client would then pull the sprite texture from it's assets by ID and draw it in the given location.

Please note that I never tried myself at a 2D engine so this suggestion is probably not really the optimal solution

This should probably be in the Multiplayer and Networking section. There are a few ways to handle what you're describing.

Assuming you have a hash grid with uniform cell size then you just need to use the player's current camera on the server to collect all the entities in range. That just requires iterating through the cells and performing a look-up in the hash grid. Then for all the cells that exist in the hash grid union the entities into a list. This list represents all the entities the client can see. I have a tutorial on spatial partitioning and the queries here. That said the basic query function would look like this in C#:

public HashSet<IGridEntity> Query(AxisAlignedBoundaryBox aabb)

{
    var entities = new HashSet<IGridEntity>();
 
    var startX = (int)(aabb.MinX / CellSize);
    var endX = (int)(aabb.MaxX / CellSize);
    var startY = (int)(aabb.MinY / CellSize);
    var endY = (int)(aabb.MaxY / CellSize);
 
    for (var x = startX; x <= endX; ++x)
    {
        for (var y = startY; y <= endY; ++y)
        {
            Cell cell;
            if (grid.TryGetValue(y * dimensions + x, out cell))
            {
                entities.UnionWith(cell.Entities);
            }
        }
    }
    return entities;

}

Thank you guys very much for your quick replies, I will definitely check out the links you posted. Storing an array of previously known entities seems to be a very workable solution, as I was having trouble visualizing what state information would be going over the network. This should start me in the right direction, thanks!