tid_print

The FARJAN's print stage — the last thing that happens to a TIDES frame before the letterbox goes on it.

It is one post-process pass, added by preseed/tides/light.module at priority 75. That number places it after the tonemap (60) and the vignette (70) and before the demo's letterbox-and-fade pass (200), which means it works on display-referred pixels — everything is already in 0..1 — and it cannot lift the black bars.

What it does

Chromatic aberration. The demo's shared Fx.grade matches its table against PP.PRESETS, which has no chromatic_aberration entry, so the brief's value was being read and dropped without a word. The displacement is radial and goes as the square of the distance from centre, which is the shape a simple achromat leaves behind: nothing on the optical axis, most at the corners. Green stays put and red and blue are fetched either side of it, so the luminance edge does not move and the picture reads fringed rather than soft.

The print black. c' = floor + (1 - floor) * c — the toe lifts, the highlight does not. A frame with a real black point still has a specular that reaches 1.0. The floor is warm-neutral and leans blue as the squall closes, because what is left in a shadow at sunset over water is sky.

The dither. Two independent hashes of the pixel, differenced, which is a triangular PDF: it decorrelates the 8-bit quantisation error instead of smearing it, and it costs two sines. Applied last, where the quantisation actually happens.

Owned by

The LIGHT lane of part 9 (TIDES). light.module adds it in M.enter, drives floor_* and dither every frame from printGrade(t), and removes it in M.exit — the post stack is scene-wide, and a pass left running here is a pass the next part is graded through.