Bespoke water texture

[anton-makarevich]

with bank/beach rendering
similar to this:

[anton-makarevich]

/oc describe how technically textures should be updated/replaced in the mmtx file

[opencode-agent]

Water textures in the MMTX format use a bitmask-based blending system rather than a single overlay image. Here's the technical approach:

How Water Textures Work

Water is rendered as a separate layer (at Z-index 18, below overlays at 20) using canonical bitmask textures. For each hex with water, the engine computes a 6-bit mask by checking all 6 neighboring hexes for water, then canonicalizes it (rotates to the lowest numeric value). The texture file is named by that 6-bit binary string.

File Path Convention

terrains/water/{6bit-mask}.png              # variant 0
terrains/water/{6bit-mask}-{variant}.png    # variant 1+

Where {6bit-mask} is the canonical bitmask padded to 6 digits, e.g.:

• 000000.png — isolated water (no water neighbors)
• 000001.png — 1 water neighbor
• 000011.png — 2 adjacent water neighbors
• 010101.png — alternating water neighbors
• 111111.png — all 6 neighbors are water

Updating/Replacing Textures

To add or replace water textures in an .mmtx file (which is just a ZIP archive):

1. Open the .mmtx as a ZIP — any ZIP tool works
2. Replace or add PNGs under terrains/water/ with the correct 6-bit binary filenames
3. The texture is rotated by -RotationSteps * 60° at render time, so each texture only needs to cover one canonical rotation — the engine handles the rest
4. Variant support: add -1, -2 etc. suffixes for multiple variants of the same mask; the engine selects deterministically via SHA256 hash

Current Assets

The existing grasslands.mmtx already contains 15 water bitmask textures (all canonical 6-bit patterns from 000000 through 111111). To customize, you'd replace those PNGs with your own art that follows the same bitmask convention — each file should depict water filling the hex up to the edges corresponding to the 1-bits in the mask (where adjacent hexes are also water).

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