Choosing a scale

Scale is the most consequential setting in Meld. It decides how many real-world metres one Minecraft block represents, and through that it decides how big your world is on disk, how long it takes to render, and which details can physically exist at all. This page explains what the number really does, so you can pick it once and not regret it.

Why scale matters

At 1:1, one block is one metre: a real 10 m wide street is 10 blocks wide, and buildings come out life-sized. At 1:10, one block is ten metres: the same street is one block wide, and a whole city fits in a walkable map. The catch is that area cost grows with the square of the ratio. Going from 1:10 to 1:1 makes the same selection 100 times more blocks, disk and render time. That is why “the whole country at 1:1” is usually the wrong first move, and why Meld’s new projects default to 1:10.

Meld shows you what you picked in plain terms: the scale field reads out the live ratio (for example 1:10), what one block means in metres, and how wide a 1 km city becomes. Since Meld 1.9.1 the value is validated too: the generator accepts 0.01 to 4.0 (1:100 up to 4:1), and Meld clamps anything outside that range instead of letting a country render fail cell by cell.

How it works: what changes with scale

The generator changes behaviour at known thresholds, so small-scale worlds stay readable instead of turning to noise:

• Bridges flatten at 1:3 and smaller. At scale ≤ 0.3 every bridge becomes a flat one-block deck that hugs the terrain, because a rising arch with columns collapses into clutter over a span a few blocks long.
• Stray causeways get drowned. At small scales, untagged roads and tracks that would paint a one-block line straight across a lake or river are submerged instead. Real shores, islands and tagged bridges are kept.
• Props are gated at 0.35. Schematic props are fixed-size builds, so a parked crane at 1:10 would be the size of a district. Below the gate they are skipped, and Meld warns you the moment a project’s scale falls under it. You can move the gate yourself with the prop scale control.
• Tree sizes follow the scale. The region tree packs place five height tiers; the large tiers are gated off at small scales, and giant trees only appear at 1:1, so a 1:10 city does not sprout 40-block oaks.
• Elevation detail matches automatically. The elevation zoom chooser’s Auto mode picks the terrain resolution your scale can actually use (1:1 picks z15, 1:10 picks z13), so you get the right detail with no wasted downloads. Details in Elevation & terrain.
• Relief flattens, and you can bring it back. Dividing height by 10 turns real mountains into bumps. The terrain height multiplier (vertical exaggeration) raises height only, not the map footprint; x2 to x2.5 makes a 1:10 mountain range read as mountains again. See Terrain & snow.

The cost side

Meld prices a plan before it runs, and two of the constants behind the estimate are measured: a baked OSM tile averages about 15.7 MB on disk (a dense city tile can be 88 times a rural one), and baking data needs roughly 2.2 GB of memory per GB of .pbf, per worker. There is also a hard sanity cap: a selection that plans past roughly 20,000 cells (the entire planet at 1:1 would be about 200 million) is refused with what to change, bigger cells, smaller scale or a smaller area, rather than letting the plan eat all your RAM. Power users can raise it with MELD_MAX_PLAN_CELLS.

How to choose

• 1:1, a city block, a campus, a landmark, your neighbourhood. Life-sized streets, full building detail, props and giant trees available. Keep the area modest.
• 1:10, a whole city or a small region. The sweet spot for walkable overviews; the bundled Scaled 1:10 preset ships tuned for exactly this (compact roads, props off).
• 1:20 and smaller, a country or a coastline. Terrain and water dominate; consider vertical exaggeration, and lean on baked data packs because you will render a lot of cells.

Two habits save the most time. First, run a Test build (it renders just the few cells at the centre of your selection) before committing to the full run. Second, decide the scale before the big render, not after: scale is a world invariant, so changing it means regenerating, and mixing scales in one world is not a thing.