OBJ to PLY Converter

What the PLY file contains

The converter reads the OBJ in the browser and writes a single binary PLY (format binary_big_endian 1.0). The header lists element vertex and element face. Each vertex has x, y, and z, plus nx, ny, and nz. Each face is a triangle stored as property list uchar int vertex_index. Object and group names from the OBJ are not stored: every mesh is combined into one vertex list and one face list, with face indices offset so the parts stay connected to the right vertices.

Positions are copied as they are. Neither OBJ nor PLY defines units or an up axis, so a model built in millimeters is still in millimeters, and a Y-up OBJ stays Y-up. Blender, MeshLab, and CloudCompare open this binary big-endian file directly.

UVs, normals, and vertex colors

• UV coordinates are written as property float s and property float t when faces reference vt values. The texture image is not embedded, so reassign the map in your 3D app after import.
• Normals come from vn lines when the OBJ has them. If it does not, a flat normal is computed for each triangle and written anyway, so the PLY still has nx, ny, and nz.
• Vertex colors are kept only when vertices use the extended form v x y z r g b. They become uchar red, green, and blue. A plain OBJ with only xyz has no vertex colors.
• MTL files are not read. usemtl names, material colors, and map_Kd images are dropped. Keep the original OBJ and MTL if you still need those materials.

Quads, lines, and point data

Faces with more than three vertices are split into triangles by fanning from the first vertex. One quad becomes two triangles, so the PLY face count is higher than the OBJ face count on meshes that were not already triangulated.

OBJ line primitives (l) are omitted. A file made only of points (p) becomes a PLY point cloud with no faces. If the same OBJ mixes a surface with point primitives, faces are omitted for the whole file, because this exporter writes either a triangle mesh or a point cloud. Delete the p lines first when you need the surface.

When OBJ to PLY is the right export

PLY is the exchange format for MeshLab, CloudCompare, Open3D, and a lot of scan and research scripts. Binary PLY is also smaller than the same mesh stored as ASCII OBJ. Use this route when the next tool wants a mesh with faces, and optionally per-vertex normals, UVs, or colors.

Keep GLB when the destination is a web viewer, Unity, or Unreal. Those importers expect a scene file, and this PLY will not carry the MTL. If you need the mesh back as OBJ later, the PLY to OBJ converter can reverse the geometry, but the round trip stays triangulated and still has no materials.

FAQ