How does Cesium read the local file for zoom in/out?

CesiumJS
1

HI, I am new to Cesiumjs. I want study the code of cesium. Let say we have our own local image file. How does cesium know which file to load when zoom in/out? I look the sample of cesium image data, they don't have geo reference information. When I create the view, I do like:
imageryProvider : new Cesium.BingMapsImageryProvider({ url : "earth/texture/"})
where earth/texture is the image file located.

Thanks

2

Hello,

The imagery is represented as QuadTrees. For each level of detail, there are 4 child tiles that occupy the space of the parent’s tile. For a visual representation of what this looks like in Cesium, toggle on ‘Tile Coordinates’ in this example:

Also, we have a SingleTileImageryProvider if you did have an image and wanted to display it on the globe. That is used to add the Cesium image in the above demo.

Best,

Hannah

3

Hi, Hannah,
Thank you for your response, I am still not sure how does cesium engine know which file to load. In the example, we are seeing level 2, L2X3Y1 and I zoom in to level3, there are several L3 file contained, like L3X5Y3, L3X6Y3, L3X7Y3. My questions is how does the engine know my file structure? Is it through a JSON file? What if my file name is like: 2001,jpg, 2002, 2003, 2004 for level 2, and 30001,jpg, 30002 … for level 3? which follows the QuadTree rule. There got to be someway that engine know the file structure.

Thank you.

4

That particular detail varies depending on the ImageryProvider.
We have the UrlTemplateImageryProvider that lets you create a URL template where X and Y are the tile coordinates and Z is the level. You can use that to define your own URL that matches with your files.

-Hannah