Knowing nothing more about the scene, we have to guess.

With smooth polygons enabled, and min shading rate = .2, you're asking the renderer to produce approximately 5 micro-polygons for each pixel in your render. This can be fine, or it can be a disaster, depending on the apparent size of the largest polygon in the scene. For example, the Poser ground plane has rather large polygons. The renderer subdivides all of a polygon if any part of it is visible. Placing the camera low to the ground, and at a shallow angle of view (i.e. nearly horizontal) you can easily end up with a lot of micro-polygons. The ground plane alone can easily reach over 250 MB of RAM. While experimenting with this phenomenon, I have successfully consumed over 1.5 GB of RAM using just the Poser one-sided square and nothing else in the scene. This makes Poser crash.

But that's just a guess. Without knowledge of your render dimensions, the actual geometry, and the camera viewpoint, it's really hard to judge if this is an issue or not.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)