+// These are found through a simple grid search on some MPI-Sintel data,
+// although the error (EPE) seems to be fairly insensitive to the precise values.
+// Only the relative values matter, so we fix alpha (the smoothness constant)
+// at unity and tweak the others.
+float vr_alpha = 1.0f, vr_delta = 0.25f, vr_gamma = 0.25f;