OBJ to schem converter: turn a 3D model into Minecraft blocks

An .obj file describes a surface: vertices, faces and texture coordinates, with the colors kept in a separate .mtl file and its images. Minecraft needs a grid of blocks instead. The converter fits your model into a grid whose longest axis matches the size you choose, fills the cells the model occupies and reads the texture color at each position.

Each color is then matched to a Minecraft block in LAB color space, which is built around how people perceive color differences. That keeps rust, skin tones and foliage recognizable once they turn into blocks. The result is written as a Sponge v3 .schem, readable by WorldEdit, FastAsyncWorldEdit, Litematica and Axiom.

Many conversion problems start in the file rather than in the settings. A few checks before uploading save several rounds of trial and error:

Also close any holes in the mesh. Open or single-sided surfaces can leave gaps once the model becomes blocks.

Size is the number of blocks on the longest axis, from 5 to 80. Four presets cover the usual cases: S (15) for a small decoration, M (25) for a prop or a vehicle, L (40) for a statue at spawn and XL (60), the default, for a centerpiece.

Block count grows much faster than size: doubling the size multiplies the volume by eight. Start small, check the silhouette, then scale up.

The color setting decides how many distinct colors are kept, starting at 4, with 16 by default. Fewer colors give flat, clean areas that suit stylized models. More colors keep gradients, but on a busy texture they also create speckles.

Color blocks and stone are always part of the conversion. Stairs and slabs are on by default and can be switched off for a full-block look.

Palette presets fill the list of allowed blocks in one click: Concrete (the default, 16 concrete colors), Terrain, Rock, Planks, Wool, Earth tones, Copper+, Honey home, Jungle, Sculk and The End. You can also type your own allowed list, and a list of forbidden blocks keeps things like diamond blocks or obsidian out of the result.

Auto-fit stairs swaps the top step of each slope for a stair block facing the right way, which smooths domes, hulls and curved roofs. It needs materials with stair variants, such as planks, stone or bricks, so it does nothing on the concrete-only default. It applies to the Java .schem only.

Once the file is uploaded, a voxelized 3D preview renders in the browser and updates when you change the size, the color count or the block families. A label recalls the current size and color count.

The block palette panel lists every block the conversion used, with a search field. Click a block to swap it for another Minecraft texture everywhere it appears, or delete it to turn it into air. Ctrl+Z undoes the last change, and your replacements are applied to the exported file.

Advanced voxelization adds two options that affect both preview and export. Block variation breaks up flat areas with neighboring palette blocks, with a patch size and an option to vary hue too. Hollow mode keeps an outer shell 1 to 8 blocks thick, for 5 to 10 times fewer blocks on a solid model.

When the preview looks wrong, the cause is usually on this list:

If a model still converts badly, try a small size first: it shows quickly whether the geometry or the settings are to blame.