When overlaying an image of North America that isn’t meant to be displayed on a 3D globe, I can get the top of the image to lineup with lat/long but the bottom is all stretched out.
Is there a way to adjust every corner of an overlayed image in stead of just N/W/S/E ?
What you’re describing sounds like your image is using a different map projection than Cesium expects. Cesium prefers the geographic projection (EPSG:4326), but some imagery providers can also use web Mercator (EPSG:3857). You can use tools like GDAL to reproject an image from one map projection to another.
You might be able to adjust corners by using a texture polygon, but it’s pretty unlikely this would give you good results, assuming I’m right that the problem is a difference of map projection. There’s a lot more to a projection change than adjusting corner points.