Why Does PTGui Write to the Hard Drive So Much?

[eboyer7]

Hi. I use PTGui to make panoramic images on my mac and something I've been wondering about for a while is why the program writes to the hard drive so much? While stitching a pano I often open up Activity Monitor to see how much ram and CPU are being used, and to see how much reading and writing is being done from the disk. Ram and CPU usage usually make sense, but the way PTGui uses the disk doesn't make sense to me. Basically, it is writing to the disk almost continuously at the full speed of the disk for most of the stitching process. Every once in a while the program reads from the disk, but it seems that it's writing to disk 90% of the time and reading 10%. For example, when stitching a 10000x5000 pixel panorama PTGui will write upwards of 1 GB to the disk, and read 100MB back. Why would it do this? Why would it write so much to the disk and never read it again?

-Eric