file:/// protocol when using Cesium off the web

[TomPed]

This issue has to do with Cesium being used off the web, i.e., Electron and Cordova trying to load the Natural Earth II imagery.

When you try loading the offline imagery you get this error: net::ERR_FILE_NOT_FOUND. One of the files not found are: file://users/tpedbereznak/Cesium-Editor/node_modules/cesium/Build/CesiumUnminified/Assets/Textures/NaturalEarthII/tilemapresource.xml. If you change file:// to file:/// then the file is found. Knowing this I made a hacky fix.

In loadXML.js I change line line 37: url : url, to url : url.slice(0, 7) + "/" + url.slice(7),.

In UrlTemplateImageryProvider.prototype.reinitialize I changed line line 504: that._url = properties.url; to that._url = properties.url.slice(0, 7) + "/" + properties.url.slice(7);

Now url's with file:// with be changed to file:/// and load the Natural Imagery II. How can this be fixed without this hacky solution?

[mramato]

What does the code you are using to load the imagery look like? I suspect this is a problem at the app level.

[TomPed]

I just select Natural Earth II from the imagery picker. No code for that.

[mramato]

Are you setting CESIUM_BASE_URL in your app?

[TomPed]

No, I'm not. Where should I be setting this?

[mramato]

I'm not sure that's the problem; I'm just trying to figure out what the issue could be.

[TomPed]

I just tried Cesium.buildModuleUrl.setBaseUrl('./node_modules/cesium/Build/CesiumUnminified');. I think we can rule this out.

[mramato]

If you wanted to try setting it, I would use the absolute path with the 3 slashes.

[TomPed]

I tried: Cesium.buildModuleUrl.setBaseUrl('file:///Users/tpedbereznak/Electron-Cesium-Starter-Kit/node_modules/cesium/Build/Cesium');. Did not work either.

[hpinkos]

@TomPed is this still a problem or did you find a solution?

[TomPed]

Yes, this is still a problem, I have that hacky fix that I mentioned, but that's it.

[hpinkos]

Okay thanks, just checking =)

[twpayne]

I think the problem here that file:// URLs can only use absolute paths. See the Wikipedia article on the file URI scheme for more information, but the tl;dr is that file://users/tpedbereznak/Cesium-Editor/node_modules/... URI does not work because it interprets users as a hostname and /tpedbereznak/Cesium-Editor/node_modules/... as an absolute path on that host, which obviously fails (neither the host nor the path exists).

By hacking in an extra /, you change this to an absolute path that only works on your machine.

Instead, I suggest that you use a relative URL, without specifying the protocol (i.e. without file://) and make sure that you're not calling require.toUrl or similar function. You will need to find the correct relative URL.

I don't think this is a bug in Cesium.

[emackey]

Cesium depends too heavily on XHR. It will never work from the file protocol.

[mramato]

@emackey Just to clarify, XHR and Cesium works great with the file protocol, obviously it won't work when running in the browser Sandbox, but for offline web-based containers, like Electron, the whole point is to read off of the file system.

I think @twpayne is correct here and it was simply an error in the electron app itself.

[pjcozzi]

@twpayne can you open a PR to fix the demo app? https://github.com/TomPed/Electron-Cesium-Starter-Kit

[Enoooch]

Using three slashes file:/// works on Windows, two slashes file:// works on Mac.

Tested in cesium 1.87 new Cesium.Cesium3DTileset().