3D file viewer for seven formats at once

For 3D printing, 3MF if the slicer accepts it and STL if it does not: 3MF carries units, colour and the arrangement on the plate, while STL carries none of that and is still the safest thing to hand a stranger. For the web or a game engine, GLB, because it packs geometry, materials and textures into one file that cannot arrive incomplete. For moving a model between modelling packages with named parts intact, OBJ if it is static, FBX if it has a skeleton. PLY is the odd one out and is not really an interchange format at all — it is what scanners write.

Because the colour was probably not inside the file you dropped. OBJ keeps materials in a separate .mtl and textures in image files next to it; a .gltf points at a .bin and its textures the same way. Nothing is broken — that is the format working as designed, and the fix is to hand over the rest of the set: select the siblings together, drop the folder, or drop a zip, and they are read from memory. GLB, 3MF and PLY are the three here that carry appearance inside the single file, and the line under the viewport tells you which kind you have.

They are two different ways a file stores appearance, and they behave differently downstream. Vertex colours attach a colour to each point of the mesh and interpolate across the triangle — that is what a scanner produces, and it survives any conversion that keeps vertices. Textured means an image is wrapped onto the surface using UV coordinates, which is what a game asset uses; it is far more detailed and it breaks the moment the image file is separated from the mesh. A file can have neither, which is most engineering geometry.

Not yet, and the reason differs by format. STEP and DXF are not meshes at all — they store real curves and surfaces, and reading them means implementing a CAD kernel rather than a mesh parser, which is being worked on separately. SKP is SketchUp's own undocumented container. 3DS is a dead Autodesk format that almost everything can re-export. When those readers exist they will appear as their own pages rather than being quietly folded into this one.

There is no fixed ceiling, because there is no server whose capacity would set one. What there is, past 100 MB, is a warning: three copies of the model coexist while you look at it — the raw bytes, the parsed triangle list and the buffers the graphics card holds — and a tab that exhausts its memory closes without warning of its own. So the numbers are put in front of you and the decision is yours. In binary STL, 100 MB is roughly 2 million triangles; in ASCII formats such as OBJ the same geometry takes several times more bytes, so the slow point arrives sooner.

No. GLB, glTF and FBX can all carry skeletons, animation clips and lights, and this page reads the geometry and materials out of them and ignores the rest — the model is shown in its bind pose under this page's own three-light setup. That is a deliberate scope: the tool exists to tell you what a file contains dimensionally, not to be a playback engine. If a rig is what you are checking, a modelling package is the right place.