Import a heightmap and the right biome masks

Import the elevation

1. Save a copy of your map. In Map Editor, choose the climate, size and ratio before editing; these cannot be changed inside the editor.
2. Prepare a 16-bit grayscale PNG, not a color screenshot or a renamed JPEG. Match the target resolution: Small 1:1 uses 2049 × 2049 pixels, Medium 1:1 uses 2817 × 2817, and Very Large 1:1 uses 4097 × 4097. For other ratios, use the official resolution table linked below. One pixel is a terrain corner: length in meters is (pixels − 1) × 4.
3. Open the heightmap import tool and its folder button. Put the PNG in the opened heightmaps folder under userdata, then select it in Import. The Steam userdata root contains 3493540/local; it is not the game's installation directory.
4. Set Minimum Height for black and Maximum Height for white. Choose Water Level deliberately; the manual recommends 0 for material/biome results. Inspect the preview before importing. Enable Keep Assets only if you intend to retain placed scenery.
5. Click Import. Wait for generation to finish and inspect the coast, hills and terrain scale before adding towns or fine scenery.

Import biomes, rivers and mountain masks

1. Generate a temporary map with the same climate and generator. In its Export tab, enable Biomes Data and export a sample. Keep those original files as a known baseline.
2. Use the folder button in the Biomes import controls to open biomes. Edit copies of the exported masks instead of copying your elevation PNG into every field.
3. The Biomes mask divides grayscale values into equal intervals for the generator's biome count. Other offered masks use black/white data. Match each file to its named entry; the available entries depend on the selected generator.
4. Select the mask files, check the legend and map preview, then Apply. If Apply is disabled, first try the unedited masks exported from that generator. Compare dimensions, image mode and assigned fields with that baseline. The player report does not establish one universal cause for a disabled button.

How to tell it worked

The terrain matches your elevation preview, and the applied masks put the intended biomes in the intended regions. Save Map under a new name, reload it and confirm the result persists. Importing terrain does not automatically recreate a real place's towns, industries or transport lines.

If the file is missing or Apply stays disabled

Missing elevation file: reopen the game's folder button, confirm the PNG is in heightmaps, and compare resolution and grayscale mode. Wrong terrain scale: recheck both height limits and map size. Mask failure with a valid exported baseline: keep the original map and record build, climate/generator, file dimensions and the affected field for support. Do not erase the map or assume TF2 folder instructions apply.