Sign-preserving exponent makes near pixels take negative offset, which
inverts depth (near recedes) with a positive divergence. Negative values
restore the original look, so the widget now accepts -5.0..0.0 with
-2.5 as default.
Adds a batch variant that keeps one ffmpeg writer alive across requeued
runs via meta_batch.outputs, so long videos stream to disk instead of
accumulating frames in RAM. Fixes the 48-byte truncated mp4 left behind
by an interrupted batch.
Negative normalized depth raised to a non-integer exponent yields NaN.
With convergence_point=1 the depth range is entirely [-1,0], so any
slider value like 2.5 poisoned the polyline sort and flattened every
row to a constant, producing identical left/right halves.
Adds spow() mirroring the sign*abs**e form the GPU paths already used,
replacing the raw ** at six call sites (enhanced_inverse, naive_mapping,
inverse_mapping, apply_inverse, apply_naive, apply_polylines).
Lukas Schmidt