Sea Power Topographic Map

Get it on the Steam Workshop – requires Anchor Chain.

A mod for Sea Power: Naval Combat in the Missile Age that makes land heights and sea depths readable on the tactical map – for low-level flying, terrain masking and radar horizons, and for where a submarine has room to dive.

The stock map colours land only with its satellite-style texture and a faint slope shade, and paints all water one flat colour: high ground is hard to judge and the seabed can't be seen at all. This mod adds a Topography layer:

• Land tinted by height in 13 bands (0 – 4000 m: greens, yellow, browns, grey, white), hill shading lit from the north-west, and contour lines whose step follows the zoom (20 m close in … 1000 m zoomed out, every fifth bold).
• Sea tinted by depth in 12 bands (0 – 6000 m), the deeper the darker, with faint seabed relief and a thin depth line at every band edge – banks, shelf edges and basins stand out like on a chart.
• 18 looks, light and dark, in a picker next to the legend (or Shift+F6): the map theme you are in decides which list it shows. Day: Standard (the original), Atlas, Army tactical map, Paper sea chart, ECDIS day, Parchment, Glacier. Night: Midnight (the default), Standard, Quiet, Black, Atlas dusk, ECDIS dusk, Combat display, Phosphor green, Red light, Thermal imager, Neon. The chart looks draw land flat with its contours and coastline and the sea in the four depth shades of a chart with a bold safety contour (the ECDIS ones in the real IHO S-52 colours).
• Looks of your own from theme files: the picker's Save this look as a theme file writes the look on the map as a small text file in BepInEx\config\SeaPowerTopo\themes; edit it (or write one that starts from another look with Base= and only lists what differs), save – the map reloads it at once. Format and every key: docs/themes.md.
• Height under the cursor – terrain height in m and ft (or the sea depth) next to the mouse pointer.
• Terrain above the selected aircraft – with an aircraft or helicopter in the air selected, terrain as high as or higher than its altitude is hatched red, and the readout gives the clearance ("Viper 2-1 clears it by 210 m").
• Thermal layer for the selected submarine – teal where the submarine, at its current depth, is below the game's thermal layer (hidden from hull sonars above it), faint teal where the layer is deeper, a thin line where the layer area ends (the game's 0.2° squares blend softly, the change lies on each square's edge). Water shallower than the submarine is hatched red; the readout adds the layer depth and the water under the keel.
• No drawing while zoomed out – at mission start the area around all units and the whole world are drawn once in the background. Zoomed out they are simply shown; closer in the view is drawn live, and the pre-drawn colours fill the edges while it catches up with a pan.
• Legend behind a small button at the bottom right of the map, above the scale.

All heights and depths are the ones the simulation itself uses: the game's own terrain data (the DEM), including the terrain height multiplier and under-water depth factor from Options → World. Unit symbols, waypoints and labels stay on top; the stock coastline is untouched. The map's night theme gets its own looks (Midnight by default).

Installation

1. Install Anchor Chain, the Sea Power community mod loader, following its installation guide (one manual step: copy its preloader into the game folder).
2. Subscribe to Sea Power Topographic Map on the Steam Workshop.
3. Start the game. In a mission, open the map: the layer is on. Toggle it in the map menu (≡) → Map Layers → Topography, or with F6. The look button at the bottom right (next to Legend) names the look and opens the list of looks; Shift+F6 goes to the next one.

Manual install instead of the Workshop: put SeaPowerTopo.dll and _info.ini into <Sea Power>\Sea Power_Data\StreamingAssets\SeaPowerTopo\.

Settings

<Sea Power>\BepInEx\config\dev.sewerlabs.seapowertopo.cfg (created on the first start; changes apply on the next redraw):

Setting	What it does
Toggle key	Key for the layer (default F6)
Look (day map), Look (night map), Look key	The look for each map theme (Standard / Midnight by default; also set by the look button and Shift+F6); a look from a theme file is named by its Id
Chart safety contour	For the chart looks: the bold contour in metres (default 30); the shallowest water shade ends at a sixth of it, the deepest begins at three and a third times it
Opacity, Hill shading	How strongly the colours and the relief cover the stock map
Contour lines, Contour interval	Contours on/off; fixed step in metres or 0 = follows the zoom
Height bands, Depth bands	Lower edges of the colour bands in metres
Sea depth	Tint the sea by depth, or leave it to the stock map
Terrain above selected aircraft	The red highlight and clearance readout
Thermal layer for selected submarine	The thermal layer, shallow-water hatching and keel readout
Resolution	Overlay resolution relative to the map's (lower = faster)
Pre-draw mission area	Draw the mission area and the world once at mission start (less drawing while playing)
Height under cursor, Legend, Units	Readout on/off, legend button, metres / feet / both

Compatibility

• Sea Power 0.8.x. The game updates often; if an update moves something the mod hooks into, the affected part stops and the log says why – the game itself keeps running.
• Works together with Better TacMap (separate map layer numbers).
• No game files are changed. Uninstall by unsubscribing (or deleting the folder).

Problems: <Sea Power>\BepInEx\LogOutput.log has a line for every step the mod takes ([Info :SeaPowerTopo]); please attach it to a bug report.

Building from source

Requires the .NET SDK 8, Sea Power installed, and Anchor Chain subscribed (the build references the game's and Anchor Chain's assemblies).

dotnet build src/SeaPowerTopo/SeaPowerTopo.csproj -c Release -p:GameDir="C:\Program Files (x86)\Steam\steamapps\common\Sea Power"

The build copies the mod into <Sea Power>\Sea Power_Data\StreamingAssets\SeaPowerTopo\ (-p:Deploy=false to skip). GameDir can also be set as an environment variable. Release packaging and the Workshop upload are described in docs/workshop.md; in-game test checklists are in docs/testing.md.

Offline preview with the plugin's own colouring code and the game's terrain files – handy for tuning colours:

dotnet run --project tools/topo-preview -c Release -- --at 61.5,8 --span 2 --size 1600x900 --out norway.png

(--at lat,lon of the centre, --span view height in degrees; --theme atlas (any id from src/SeaPowerTopo/Render/Theme.cs; without it Standard by day, --dark Midnight), --theme-file my.ini or --themes-dir <folder> + --theme <id> for theme files, --check-themes to test them, --chart-safety 50; --danger 1200 adds the aircraft highlight, --interval 100 a fixed contour step, --nodepth leaves the sea to the stock map, --depth-factor 2 is the game's under-water depth factor, --sub 120 what a submarine at 120 m sees – with a stand-in for the game's random layer depths, which need Unity – --game <dir> the game folder.)

How it works

The stock map is a Unity scene of lon/lat quads that a camera renders into the texture the map window shows (SeaPower.LiveMap). The mod adds transparent quads to that scene, so the overlay pans, zooms and wraps with the map for free. Every layer is drawn the same way: heights copied out of the game's DEM on the main thread in 3 ms slices per frame (the 30″ chunks the map has loaded, via TerrainLoader.TryGetCached; the 3′ world grid when zoomed out), then resampled (Catmull-Rom when zoomed in past the DEM) and coloured on half the CPU cores (a 4K view in about 70 ms). The pre-drawn layers (mission area ×1, ×4, ×16 and the world at 0.1°, up to 8 megapixels each, with mipmaps) stand in for the live layer while the view's scale is within 1.4× zoomed in or 3× zoomed out of theirs. The live layer's image covers the view plus a margin (15–40 %, as much as an 8-megapixel budget allows) and is redrawn when the view leaves it, when a pan has used up most of the margin, or when the zoom changes a lot. Layers in front cut holes into the ones behind (their mesh is the image minus the others' rectangles), so the translucent colours never stack. The thermal layer comes from the game's own tile cache where a tile is settled (Environment._layerDepths), otherwise from the same rule and the same seeded UnityEngine.Random draw, with the generator's state put back. A look is a plain parameter set (Render/Theme.cs): key colours spread over the height bands, in steps or blended, or one flat colour; relief strength with a tinted shadow and highlight; contour lines with an optional glow; a coastline; the sea's key colours or a chart's four depth shades; depth lines. The first release's look is one of them, drawn by its original rules (its output is byte for byte unchanged). Adding a look is adding such a block, or a theme file: Render/ThemeIni.cs reads and writes the file format and Render/ThemeLibrary.cs finds the files, resolves Base=, keeps the last working version of a file that breaks, and swaps the result into Themes when the folder changes (polled every 1.5 s); both are plain C# and tested offline by the preview tool's --check-themes. The legend, the look button and its list and the cursor readout are Noesis elements laid over the map control, handed over by a Harmony postfix on RenderedLayer.OnRender that is applied only once NoesisGUI runs.

Depths are the simulation's: the DEM depth times the game's under-water depth factor, doubled once more where the DEM is shallower than 48 m (as every terrain lookup of the game does) – so a thin ring of shallower water can sit just outside a coastal strip. That is how the simulation sees the seabed, not a drawing error.

src/SeaPowerTopo/
  Plugin.cs, Patches.cs      entry point (Anchor Chain plugin); mission start/end hooks, the late map hook
  TopoHost.cs                per-frame driver: layer entry, toggle key, selected aircraft / submarine, which overlay
                             layers show and draw, pre-drawn areas from the units, legend/readout
  TopoLayer.cs               the Topography entry in the map's Layers menu
  Terrain/HeightReader.cs    reads DEM chunks and the world grid (main thread), height under a point
  Terrain/LayerMap.cs        the game's thermal layer per 0.2° tile
  Render/OverlayRenderer.cs  one overlay layer (live or pre-drawn): quad in the map scene, redraw pipeline, holes
  Render/Cutout.cs           an image minus the layers in front of it, as rectangles
  Render/Raster.cs           resampling, tint, hill shading, contours, red hatching, sea depth, thermal layer,
                             mipmaps (worker threads, plain C#)
  Render/Palette.cs          height and depth bands and their colours
  Ui/MapDecoration.cs        legend button, legend and cursor readout (Noesis)
  mod/_info.ini              Mod Manager entry
tools/topo-preview/          offline preview (links Raster.cs and Palette.cs)
tools/package.ps1            release build → dist/SeaPowerTopo/
tools/shot-director/         dev-only plugin that scripts the Workshop screenshots (docs/workshop.md)
workshop/                    Workshop description, preview.jpg, screenshots/

License

MIT. Not affiliated with Triassic Games or MicroProse. The mod reads the game's terrain data at runtime; nothing of the game is included in this repository or in the mod.