PMod Map Preview Generator

Generates real map preview thumbnails for Bopl Battle and exposes them to other mods through a small public API.

What it does

• Captures real in-game screenshots of every vanilla map (once per map, cached as PNG in BepInEx/plugins/PmodMapPreview/)
• For BoplMapMaker custom maps: loads the map's biome scene, places the map on it and screenshots it — real thumbnails, not placeholders
• Installs the previews into the game's map selection UI automatically
• Re-generates a preview when a map is edited in the Map Maker
• Shows a progress panel at the top of the screen while previews are being generated

Reference the library

Two options:

Option A — compile-time reference (recommended)

Reference PMod.MapPreviewGenerator.dll from your project and add the dependency to your Thunderstore manifest.json:

"dependencies": ["BepInEx-BepInExPack_BoplBattle-5.4.2100", "PMod-MapPreviewGenerator-1.0.0"]

using PMod.MapPreviewGenerator;

Option B — runtime reflection (no compile-time dependency)

Resolve the type by name and call members via reflection. The type never causes a hard dependency, so your mod still works (without previews) if this one isn't installed.

static Type PreviewLib =
    AppDomain.CurrentDomain.GetAssemblies()
        .Select(a => a.GetType("PMod.MapPreviewGenerator.PreviewLibrary", false))
        .FirstOrDefault(t => t != null);

The vote mod NextMapVote ships a working example of this pattern (PreviewLibAdapter.cs).

API reference

All members are public static on the class PMod.MapPreviewGenerator.PreviewLibrary.

Lifecycle overview

The generator is fully automatic: when you enter a menu scene (buildIndex < 6) it arms a preload, captures every map that lacks a cached PNG (screenshots for vanilla maps, real biome-scene screenshots for custom maps), writes map_N.png / custom_N.png into BepInEx/plugins/PmodMapPreview/, and installs the previews into the game's map selection UI. A mod only needs to call EnsurePrepared before showing a preview and TryGetSprite to fetch it.

Identifiers

The active context is implicit: all methods below take a vanilla mapId; the custom-map section takes a customIndex. There is no overlap — custom maps are only used when CustomMapsAvailable is true.

Status & progress

Vanilla maps

BoplMapMaker custom maps

Typical usage

public class MyMapPicker : MonoBehaviour
{
    private void Start()
    {
        PreviewLibrary.PreviewReady += OnPreviewReady;
    }

    private void Update()
    {
        // Show a progress bar while generating
        int total = PreviewLibrary.PreloadTotal;
        int done = PreviewLibrary.PreloadDone;
        // ...

        // Cards: prepare lazily (no-op if already ready), then draw
        foreach (int mapId in myCandidates)
        {
            PreviewLibrary.EnsurePrepared(mapId);
            Sprite sprite;
            if (PreviewLibrary.TryGetSprite(mapId, out sprite))
            {
                // GUI.DrawTextureWithTexCoords(...)
            }
        }
    }

    private void OnPreviewReady(int mapId)
    {
        // A real preview just landed — force a repaint of that card
    }
}

Using custom maps

if (!PreviewLibrary.CustomMapsAvailable)
{
    // fall back to vanilla behaviour
    return;
}

// Show the MapMaker maps
for (int i = 0; i < PreviewLibrary.CustomMapCount; i++)
{
    PreviewLibrary.EnsureCustomPrepared(i);
    Debug.Log($"{PreviewLibrary.CustomMapName(i)} ({PreviewLibrary.CustomMapType(i)})");
}

// Make the next round play custom map #2
PreviewLibrary.CommitCustomMap(2);
// per frame until the level starts:
PreviewLibrary.EnsureCommitted(2);

Preview cache

• Location: BepInEx/plugins/PmodMapPreview/
• Vanilla: map_<levelId>.png
• Custom: custom_<customIndex>.png
• Screenshots are 640x360. Delete a PNG to force re-capture of that map on the next menu visit.

Requirements

• BepInExPack for Bopl Battle
• Optional: BoplMapMaker for custom map previews