It's been my understanding that GDAL's RasterIO (most current version) uses overviews when available, implicitly. Is this also true for VRTs and warped VRTs or is not true?
I ask because 1) in reading from a warped VRT (using vsicurl) I'm not seeing use of the overviews in the GeoTIFF source that surface in the VRT, and 2) in reading the source of gdalwarp_lib.cpp I see that it has its own code for navigating overview levels and does not rely on any implicit overviews.
failed and the overviews were skipped. Thanks for getting me back on the right track. The VRTWarpedDataset class is very handy. I'm looking forward to being able to use VSICurlClearCache in production, it'll be handy for testing my warped VRT code.