Convert STL to PLY — Smaller Files, Better Tools

No. STL is geometry-only — it physically cannot store color data. The converted PLY will have triangulated geometry and vertex normals, but no vertex colors. If you need colored PLY output, start from a format that supports color (like GLB or 3MF) or add colors manually in MeshLab after conversion: Filters > Color Creation and Processing > Per Vertex Color Function lets you paint by height, curvature, or custom expressions.

Binary PLY is typically 30–50% smaller than Binary STL for identical geometry. The reason: STL stores each triangle independently (3 vertices × 3 floats + 1 normal × 3 floats = 50 bytes per triangle), duplicating shared vertices. PLY uses indexed vertices — shared vertices are stored once and referenced by index. A 10 MB STL with 200K triangles typically becomes 5–7 MB PLY. For ASCII formats, the difference is smaller because both use text encoding.

Yes — PLY is MeshLab's native format. File > Import Mesh > select your .ply file. The mesh loads with vertex normals intact. Useful first steps: Filters > Quality Measure and Computations > Compute Geometric Measures (surface area, volume, bounding box). For mesh quality analysis: Filters > Quality Measure and Computations > Per Vertex Quality Function. To check for problems: Filters > Cleaning and Repairing > Select Non Manifold Edges. MeshLab handles PLY files up to available RAM — 50M+ vertex meshes work on 16 GB machines.

For printing itself, no — STL is the universal slicer input. PLY's advantages are upstream: mesh analysis, point cloud processing, and research workflows. The typical path is: analyze/process in PLY (MeshLab, CloudCompare), then convert back to STL for the final print. PLY is also better for archival — smaller files, indexed vertices, and extensible properties that STL lacks.

Three practical reasons: (1) File size — binary PLY is 30–50% smaller, which matters for large scan datasets or version-controlled model libraries. (2) Software compatibility — MeshLab, CloudCompare, Open3D, and most academic mesh processing tools prefer PLY as their native format. (3) Extensibility — PLY supports custom per-vertex properties (quality scores, curvature values, segmentation labels) that STL cannot store. If you're doing anything beyond "send to printer," PLY is the better working format.

Binary PLY by default. Binary is 3–5× smaller than ASCII PLY and loads faster in every tool. ASCII PLY is human-readable (you can open it in a text editor and see vertex coordinates), which is occasionally useful for debugging or scripting, but there's no practical reason to prefer it for normal workflows.