Library Breakdown

The majority of the work done in this extension happens in the following getTilePosition() function call.

PositionData memory position = getTilePosition(asteroidEntity, building);

The getTilePosition() (opens in a new tab) function dives progressively deeper into helper functions. Many of these will be included in a future Primodium library package, but they are a good source of insight as well.

• getTilePosition()
  • P_EnumToPrototype.get()
  • getAsteroidBounds()
    • Dimensions.get()
    • P_Asteroid.get()
  • canBuildOnTile()
    • P_RequiredTile.get()
    • Asteroid.getMapId()
    • P_Terrain.get()
  • canPlaceBuildingTiles()
    • P_Blueprint.get()
    • allTilesAvailable()

getAsteroidBounds()

Before we search the asteroid for a suitable tile, we need to know the x/y tile boundaries. This function finds them.

P_EnumToPrototype.get()

bytes32 copy buildingPrototype = P_EnumToPrototype.get(BuildingKey, uint8(buildingType));

We use EBuilding to track our list of building. The actual building data is stored in a Prototype table. The P_EnumToPrototype table allows us to convert these enums to prototypes, using a type key and an index.

Dimensions.get() / P_Asteroid.get()

DimensionsData memory range = Dimensions.get(ExpansionKey, asteroidLevel);

Each asteroid map has an allowed build area based on its current expansion level. This lookup table returns a DimensionsData object with the expansion related width and height parameters.

P_AsteroidData memory asteroidDims = P_Asteroid.get();

P_Asteroid tables stores the basic asteroid bounds, returned as a P_AsteroidData object.

Both of these are then combined to tell us the current bounded build range for the asteroid.

return
  Bounds({
    maxX: (asteroidDims.xBounds + range.width) / 2 - 1,
    maxY: (asteroidDims.yBounds + range.height) / 2 - 1,
    minX: (asteroidDims.xBounds - range.width) / 2,
    minY: (asteroidDims.yBounds - range.height) / 2,
  });

canBuildOnTile()

After we have the Bounds details, we loop until we find a suitable tile. This function specifically checks the type of each tile coordinate, and if it matches the building we intend to build there.

EResource resource = EResource(P_RequiredTile.get(prototype));

P_RequiredTile tells us the tile type require by the specific building we're attempting to build.

uint8 mapId = Asteroid.getMapId(coord.parentEntity);

Different asteroids have different maps. The PositionData struct contains both x/y parameters, as well as the ResourceId of the parent object. We can use that to retrieve the relevant map.

return (
  resource == EResource.NULL ||
  uint8(resource) == P_Terrain.get(mapId, coord.x, coord.y)
);

P_Terrain is another lookup table to retrieve tile details from a specific map. The rest of the comparison is checking if the tile is of the appropriate type: e.g. empty for most buildings, or a mine tile for mines.

canPlaceBuildingTiles()

Most buildings cover more than one tile. This function checks for collision and interference across the entire intended building location.

P_Blueprint.get()

int32[] memory blueprint = P_Blueprint.get(buildingPrototype);

Prototypes are translated to Blueprints for the purpose of placement. This function retrieves those Blueprint details.

The rest of this function is checking the full building size stays within the asteroid bounds.

allTilesAvailable()

return allTilesAvailable(asteroidEntity, tileCoords);

This function loops through all the building tiles, and does the actual collision checking.