Supported formats
Solidly opens fifteen file extensions across ten formats:
.gltf .glb .fbx .obj .stl .ply .usd .usda .usdc .usdz .step .stp .iges .igs .3mf
Every one of them can be viewed, inspected, rendered, and captured. What differs is how much of the file Solidly can describe, which parts of it can be changed, and whether the result can be written back.
glTF and GLB
glTF is the format Solidly supports most completely.
Inspection reaches the whole document, down to accessors, buffer views, and buffers. Editing covers the scene graph, node transforms, materials, texture bindings, material variants, and asset metadata. glTF is also the only format Solidly compresses; see Compressing glTF.
The following extensions are fully supported:
| Area | Extensions |
|---|---|
| Materials | KHR_materials_clearcoat, KHR_materials_sheen, KHR_materials_transmission, KHR_materials_volume, KHR_materials_ior, KHR_materials_specular, KHR_materials_iridescence, KHR_materials_anisotropy, KHR_materials_diffuse_transmission, KHR_materials_dispersion, KHR_materials_emissive_strength, KHR_materials_unlit, KHR_materials_pbrSpecularGlossiness |
| Textures | KHR_texture_transform, KHR_texture_basisu, EXT_texture_webp |
| Geometry | KHR_draco_mesh_compression, EXT_meshopt_compression, KHR_meshopt_compression, KHR_mesh_quantization, EXT_mesh_gpu_instancing |
| Scene | KHR_lights_punctual, KHR_materials_variants, KHR_node_visibility, KHR_animation_pointer |
| Metadata | KHR_xmp_json_ld |
An extension outside this list is reported in the Info tab with a warning symbol and is preserved through saves.
FBX
Solidly loads the node hierarchy, geometry, materials, textures whether embedded or beside the file, cameras, lights, animation takes, and both document and per-node metadata.
Editing covers node transforms, renames, deletion, duplication, reordering, material properties and texture bindings, and node metadata. Nodes, lights, and cameras can be added.
Saving re-imports the original document, applies the edits to it, and exports the same scene graph, so parts of the file Solidly does not model are carried through untouched.
Solidly normalizes an FBX scene to Y-up and centimetres when it loads. A save that carries node edits re-applies that normalization, so the written file declares the normalized axis and units. A material-only save leaves the authored axis and units alone.
OBJ
An OBJ file is read together with its .mtl and the images that file refers to. Solidly reports the objects and groups the file declares, its face, line, and point elements, its vertex data, and its smoothing groups. OBJ has no structured metadata container so authored comments are treated as the file's metadata.
Every OBJ material is loaded double-sided, which matches how the format is used in practice.
Editing covers material properties and texture bindings, node metadata, and mesh-level operations. OBJ hierarchy rows are flat geometry partitions rather than a scene graph: they can be renamed, duplicated, and deleted, a transform set on one is baked into its vertex data when the file is written, and deleting a row removes that partition.
STL and PLY
Both formats store one surface and no scene graph, so they have only the Info and Render tabs. Solidly reads ASCII and binary forms of both. PLY vertex colours, normals, and texture coordinates are read under the usual property spellings, and an STL file's ASCII solid name or readable binary header is reported as metadata.
The one editable property is orientation. The Info tab offers Auto Orient, which examines the surface and rotates it upright. Saving writes the same format back with that rotation applied to the geometry.
A PLY file with no faces or edges is drawn as a point cloud, and one written by Gaussian splatting training is drawn as splats. See Point clouds and splats.
USD
Viewing a stage allows changing what is composed: selecting variants, loading and unloading payloads, filtering display purposes, and setting subdivision complexity. Those changes are authored on an in-memory session layer, so they change what you are looking at without modifying the asset. Nothing writes back to a USD file. USD covers the format in full.
STEP and IGES
STEP and IGES files store exact surface geometry, which Solidly converts into triangles at a complexity level that can be changed in the Info tab. Solidly reads the assembly tree, part names and colours, placements, the file's unit, and the file header, and it reports each part's size, volume, and surface area.
Both formats are view-only. The toolbar adds a measuring tool that reads values from the exact geometry, a section view, and an exploded view, and none of them modifies the file. STEP and IGES covers the formats in full.
3MF
Solidly reads the 3MF core specification, the Materials and Properties extension, and the Production extension, which together cover meshes, components, colours, textures, and display properties. For a Bambu Studio or Orca Slicer project it also reads the plates, filament colours, and names the slicer stores.
3MF is view-only. Material values can be adjusted to see their effect, and those changes are not saved. 3MF covers the format in full.
MaterialX
Solidly does not open .mtlx documents, and a .mtlx file referenced by a USD layer is not listed in the Models list.
MaterialX is supported and still shades the model wherever a USD stage authors it. A stage whose materials carry a MaterialX surface output is drawn through that output, and the Render tab's Render Context control switches between it and the UsdPreviewSurface approximation. See Visualizers.
Writing files back
Save and Save As are available for glTF, GLB, FBX, OBJ, STL, and PLY, and each format offers its own set of output options. See Saving and exporting.