isleward/src/client/js/rendering/tileOpacity.js

define([
	'js/system/globals'
], function (
	globals
) {
	let noFlipTiles = null;
	let tileOpacities = null;

	return {
		initMap: function (msg) {
			noFlipTiles = msg.noFlipTiles;
			tileOpacities = msg.tileOpacities;
		},

		getSheetNum: function (tile) {
			if (tile < 224)
				return 0;
			else if (tile < 480)
				return 1;
			return 2;
		},

		getSheetName: function (tile) {
			const { clientConfig: { atlasTextures } } = globals;

			const sheetNum = this.getSheetNum(tile);
			const sheetName = atlasTextures[sheetNum];

			return sheetName;
		},

		getOffsetAndSheet: function (tile) {
			const { clientConfig: { atlasTextureDimensions, atlasTextures } } = globals;

			let offset = 0;
			let sheetName = null;

			let aLen = atlasTextures.length;
			for (let i = 0; i < aLen; i++) {
				sheetName = atlasTextures[i];

				const dimensions = atlasTextureDimensions[sheetName];
				const spriteCount = dimensions.w * dimensions.h;

				if (offset + spriteCount > tile)
					break;

				offset += spriteCount;
			}

			return {
				offset,
				sheetName
			};
		},

		map: function (tile) {
			if (tileOpacities[tile] === undefined)
				return 1;

			const { max, opacity } = tileOpacities[tile];

			let alpha = opacity;
			if (max !== undefined) {
				alpha = alpha + (Math.random() * (alpha * 0.2));
				alpha = Math.min(1, alpha);
			}

			return alpha;
		},

		canFlip: function (tile) {
			return !noFlipTiles.includes(tile + 1);
		}
	};
});