I tried with Detail decimation factor = 10 and it completed.
Then I tried setting Detail decimation factor back to 1, and had the out of memory problem again, but it crashed much sooner this time – after minutes instead of hours. I searched for RealityCapture.log but couldn’t find it. It’s not in my C:\TEMP, and C is definitely the drive with my windows installation. However, I took a screenshot and attached that in case it is helpful.
(By the way, my experience up to this point with RealityCapture has been really great!)