CELL SIZE CHANGE

CELL SIZE CHANGE

Hey folks,

Quick update for you relating to a change in terminology.

As you guys know, we construct our 3D terrain out of parcels. A parcel is a pre-constructed area of contiguous land, made out of cells that fit together like Tetris pieces. We create worlds by stitching these together so that players can move seamlessly from one to the next with no loading screen and with no limitations in terms of the players, monsters or objects that you can see across the border from one parcel to the next.

Parcel_128Cell_Town_Watermarked

This is still the case, but we recently made a technical change that will give us (and you!) more control to build worlds. Historically, the size of a cell was 256m by 256m. We’re updating that size to be 128m by 128m.

What does this mean?

First, let’s talk about what this doesn’t mean: It doesn’t mean that parcel sizes are getting smaller.

Got that?  OK, good, I just wanted to get that out of the way first!  Now, let’s explain what it does mean.

Imagine a page of grid paper. Each of those little squares represents a top-down area of 3D space in the game. The size of that space is 256m by 256m. We call these cells. Now picture drawing a box around four of those, denoting a two-cell by two-cell section of the grid. This box represents 512m by 512m of 3D space.

Next, double the number of horizontal and vertical grid lines under that box. What happens to the size of the box?  Nothing. Since the scale of the grid hasn’t changed, the box still represents the same area of 3D space -- it’s just on a more granular grid; every square has been subdivided into four smaller squares.  Instead of two cells by two cells, the box is now four cells by four cells. The total area that was represented by four cells is now represented by 16 smaller cells.

With me so far?  OK, great!

We just went through this same process with our world maps. We subdivided the world grid that we build on such that a “cell” (square of the grid) is now 128m by 128m.  A 20 cell by 20 cell world was previously divided into 400 cells. That same world is now 40 by 40, and consists of 1,600 quarter-sized (smaller) cells.

To show this in practice, here is an example of the Shire Parcel, before and after.

256 cell Shire parcel

256 cell Shire parcel

128 cell Shire parcel

128 cell Shire parcel

As you can see, the parcel shape and size in the world hasn’t changed. What HAS changed? The number of cells that parcel is divided into: instead of three cells (of 256m by 256m each), the parcel is now divided into 12 cells (128m by 128m each).

Why did we do this?

A grid that is made up of smaller cells allows us to make shapes that are more refined. That might not seem like a bit deal, but it is. Imagine that your minimum parcel size is one cell. Every parcel you wanted to build HAD to be at least 256m by 256m in size. That meant it was impossible to create a small pond, a grove or a section of road without also defining the area surrounding it.  We could already go big, since there was no limit to a parcel (in cells). Now, we can go much smaller as well and allows for more complex “Tetris shapes”. We can create a winding river to place right outside our city walls or make a swamp with sprawling tendrils that snake out across the surrounding area.

If smaller is better, why not 10m by 10m?

Now, don’t get me wrong, smaller cells are not simply better than large. This is a tough balancing act – reducing cell size has negative performance implications (e.g. the game must load them separately and stitch them together, causing more intersection points as the player runs around the world and more blending of textures to hide the seams), implications on the management of the art pipeline (4x the files to manage, which makes it harder to update things), and increases the risk that the repeating parcels will become detectable if placed too close together.

In this case, however, we suspected that we could dial the grid size down a notch (from 256m to 128m) and the pros would outweigh the cons. We believe that gamble has paid off. In addition to being able to craft more interesting parcel shapes, this also…

  • Offers more variability in world maps (because we have 4x as many pieces to mix and match),
  • Allows us to create one or more “road tile” parcels that can be used to construct roads between cities (ideal for caravans!)
  • Gives us the ability to create smaller “points of interest”, like ponds and rock outcroppings, that can be used as filler to make the world seem less empty, and
  • Grants us a finer degree of control over where to place things in the world – we can push a pond right up to the side of a village or wrap a river around the base of a mountain.

It also gives us the ability to go back to some of our parcels and add an “outskirt area” that we can use for the placement of siege equipment. That’s actually what triggered this change; we found that the best strategic locations to place strongholds were almost always up against the edge of the parcel – which means that we couldn’t guarantee enough room for siege mechanics. Now we can fix that without having to reduce parcel sizes or add enormous skirts around every parcel.

This change affects both Eternal Kingdoms and Campaign Worlds. Hopefully this makes sense, but if you have any questions please don’t hesitate to hit us up on the forums!

Todd Coleman
Creative Director, ArtCraft Entertainment

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