Assassin’s Creed: Black Flag – Waterplane (GAT #64)
Source: https://simonschreibt.de/gat/black-flag-waterplane/ Author: Simon Schreibt. Captured 2026-10-16.
Problem
- Water plane cuts through boat hulls; expensive to fully simulate fluid–hull interaction.
- Large ships: player rarely sees “belly”; small boats expose interiors.
Large ships
- Bug video shows water pushed down under hull.
- Anonymous tip: buoyancy spheres probe velocity for splash particles; water pushed by projected displacement mask—not spheres alone.
- AC3 tech articles mentioned partitioned buoyancy spheres (simulation, not the depth mask).
Small boats – Depth Mask
- Invisible “lid” geometry over boat top.
- Not stencil-only (would punch holes in waves seen from opposite side).
- Technique (DepthMask): after terrain/boat/opaque, draw invisible plane depth-only; then water fails depth test where lid wrote depth → dry interior.
- Evidence: waves taller than lid leak; foam can spawn “inside” (logic still thinks water there); disabling lid draw call reveals water in boat.
Alternatives / related
- Float boats slightly (top-down games); add belly geometry (Fallout 4).
- Battlefield 2 amphibious: early window geometry as mask; water/terrain respect mask; foam needs second window pass.
- Comments: stencil portal masking (uniform water level limitation); Minecraft 1.9 depth mask; Subnautica SDF clip; transparent polygons writing depth only.