Base layer id (0-31).
Optionaloverlay?: numberOverlay layer id (0-31). Defaults to base.
Optionalblend?: numberBase->overlay blend in [0, 1]. Default 0.
Optionalrotation?: numberUV rotation step (0-15, 22.5 deg each). Default 0.
Optionalscale?: numberUV scale step (0-7 -> 0.75x-1.33x). Default 3 (~1.0x).
Optionalautoshader?: booleanProcedural height/slope rule wins on this texel.
Pack one control-map texel (splat mode 3). Two layer ids + blend give two texture taps per texel regardless of palette size; rotation/scale detile the planar sampling frame per texel;
autoshaderhands the texel to the procedural height/slope rule.