Add support for variable tiles splitting (#1447)

Author: gkjohnson

src/three/plugins/DebugTilesPlugin.js

@@ -223,6 +223,12 @@ export class DebugTilesPlugin {
 
 		this.tiles = tiles;
 
+		if ( ! this.enabled ) {
+
+			return;
+
+		}
+
 		// initialize groups
 		const tilesGroup = tiles.group;
 		this.boxGroup = new Group();

src/three/plugins/images/ImageFormatPlugin.js

@@ -316,11 +316,12 @@ export class ImageFormatPlugin {
 		const x = tile[ TILE_X ];
 		const y = tile[ TILE_Y ];
 
-		for ( let cx = 0; cx < 2; cx ++ ) {
+		const { tileSplitX, tileSplitY } = this.tiling.getLevel( level );
+		for ( let cx = 0; cx < tileSplitX; cx ++ ) {
 
-			for ( let cy = 0; cy < 2; cy ++ ) {
+			for ( let cy = 0; cy < tileSplitY; cy ++ ) {
 
-				const child = this.createChild( 2 * x + cx, 2 * y + cy, level + 1 );
+				const child = this.createChild( tileSplitX * x + cx, tileSplitY * y + cy, level + 1 );
 				if ( child ) {
 
 					tile.children.push( child );

src/three/plugins/images/utils/TilingScheme.js

@@ -85,11 +85,16 @@ export class TilingScheme {
 
 		}
 
+		const {
+			tileSplitX = 2,
+			tileSplitY = 2,
+		} = options;
+
 		const {
 			tilePixelWidth = 256,
 			tilePixelHeight = 256,
-			tileCountX = 2 ** level,
-			tileCountY = 2 ** level,
+			tileCountX = tileSplitX ** level,
+			tileCountY = tileSplitY ** level,
 			tileBounds = null,
 		} = options;
 
@@ -112,6 +117,10 @@ export class TilingScheme {
 			tileCountX,
 			tileCountY,
 
+			// The number of tiles that the tiles at this layer split in to
+			tileSplitX,
+			tileSplitY,
+
 			// The bounds covered by the extent of the tiles at this loaded. The actual content covered by the overall tileset
 			// may be a subset of this range (eg there may be unused space).
 			tileBounds,