Four damned days!
It took so much time to render this 14-second special effect. Either I don’t understand something else in the render settings, or in professional work it takes a lot more computing power than I have. But my faithful computer stood up to the test, and the temperature gave out around its usual 38 degrees.
That, in other matters, did not prevent me from cursing this unfortunate simulation three times, when I had to sleep under the howl and shimmer of the terminator's great-great-grandfather.