The Map Editor - Part I

I'm working on the Map Editor for the Panzer Division for a while now. It's not done yet but I decided to share some of the experience, maybe somebody will find it useful or maybe somebody will spot something horribly wrong and let me know.

To understand some of the decisions we took is important to know that:

• Panzer Division is made with HTML5, CSS3 and JavaScript.
• Panzer Division is supposed to run even on the first iPad (where we are facing tough constraints especially related to the maximum canvas memory.)
• Panzer Division maps have pointy hexagonal tiles.

Intro

In Panzer Divizion the first thing you'll have to do is to choose what to play: a campaign or a scenario.

• A campaign has an associated set of scenarios.
• A scenario has an associated map.

Before we can create campaigns, we need to have scenarios. And in order to create scenarios we need maps. (Actually with one map we can create multiple scenarios, and those scenarios can be used to create campaigns.)

To create maps we need a Map Editor.
To create scenarios we need a Scenario Editor.
To create campaigns we need - what a surprise - a Campaign Editor.

The maps, scenarios and campaigns are kept on disk in some format like JSON. When the user chooses a scenario, the corresponding scenario file and map file are loaded from disk.

All the three editors have to:

1. read and parse the file and generate data structures to be used by the game.
2. allow the user to modify the data.
3. save the data back to the file.

For the moment we work on the map editor, the others are to be done later.

The Map Files

The purpose of the Map Editor is to read, modify and save map files.

A map file contains the following information:

1. map size - number of rows and columns.
2. tile data for each of the tile - indicates how a specific tile must be rendered (e.g as sea, forest, shore, etc).

Map file example:

"numberOfColumns":30,
"numberOfRows":20,
"tiles": [
 [0,0,0,0,0,0,0,0,0,0,5,11,11,11,6,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,0,0,0,0,0,0,0,10,106,106,106,106,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,0,0,0,0,0,0,10,193,176,169,159,23,6,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,0,0,5,11,6,5,16,188,217,178,178,172,106,1,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [5,6,0,5,16,33,106,22,106,193,218,238,178,156,106,7,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,106,17,16,106,106,64,106,106,188,189,208,207,196,24,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,175,158,114,110,133,100,133,117,192,199,106,191,106,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [9,155,178,165,106,130,106,64,106,106,106,106,106,24,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [9,161,160,106,145,117,106,63,106,13,14,106,106,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,9,106,128,119,106,163,60,106,18,0,3,8,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,9,113,106,106,157,174,31,106,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,3,14,106,157,178,179,165,18,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,15,162,178,167,160,106,12,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,4,106,20,160,13,14,106,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,3,2,3,2,0,3,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0], 
 [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0] ]

The tile information must also be used by the game logic to influence the unit movement (e.g rivers or swamps reduce it) or to prevent movement (e.g battleships cannot go over forests) so is important to spend a while to think about various ways to do it.

We also need a tile set image - a big image that contains all the terrain tiles. We now have a big problem: the tile set image can be very different based on the choises we make so we need to spend as little time as possible on making that tile set for the moment. My advice is to use obvious colors and big brushes to create a rude version of the tile set. I lost lots of time trying to create nice, detailed tiles only to throw them away later because I realised I need a different tile set.

Defining hexes

The map is composed of pointy hexagonal tiles. Each hex has 6 corners and 6 sides.

 S6  /\  S1
 S5 |  | S2
 S4  \/  S3

We can use either to describe the tile, for example we could use 1 for the side that matches forest and 0 for the side that is not forest.

Since there are 6 sides/corners, so we have 64 possible combinations for each type of tile, the sides index is: 000000-111111 (00-63)

The side 1 is the last significant digit, side 6 the most significant digit, like this:

S6 S5 S4 S3 S2 S1
1  1  0  1  1  0 

The many facets of the terrain

There are forests, mountains, rivers, shore, etc. How can we encode more than one terrain type in one tile data? That will be discussed in another post.