I did some more experimenting on the shadows. I upped the Resolution to Very High, and that improved the shadow of the gun. Shadow Cascades was already turned off. The strength of the upward-facing directional light didn't seem to make a difference in shadow quality. I found the Shadow Distance to be a tradeoff between gun shadow quality and where/when rock shadows appear. The distance to the edge of the platform is 400, and I had the shadow distance set to 20. So only rocks that fall directly overhead cast a shadow, and the shadow doesn't appear until just before impact. But higher values result in a bad-looking gun shadow. A value of 10 causes the rock shadows to barely appear at all. I like the idea of seeing the shadow before the impact, so 15 to 20 seems about right. I didn't look into blob shadows yet. Thanks for the help on what to tweak.