3D CAD Viewer (STL, OBJ, 3MF, glTF, PLY)
Open 3D models on your device: sections, measuring, volume, mass and a watertight check.
Try before you buy.
- Free preview: your model with a MySmartCoPilot watermark, its size, counts and watertight check, the first half of your measurements (up to 10); volume and mass are hidden.
- Locked until you unlock it: download and copy.
- Unlock: Pro pass, ₹179 for 30 days, a one-time payment that never renews.
Ways to unlock shows how to get the full result.
Printing this result is locked in the free preview.
Open a 3D model or try the sample part.
Model
Measurements
Press Measure, then click two points on the model. With “Snap to corners” on, each click takes the nearest corner of the face you hit.
Drag to turn, right-drag or Shift-drag to pan, scroll or pinch to zoom, double-click to fit. With the view focused: arrow keys turn (Shift: pan), + and − zoom, F fits; while measuring, Enter or Space picks the point under the centre cross.
Locked in the free preview. Opens the ways to unlock this result.
Locked in the free preview. Batch runs unlock with a pass.
Locked in the free preview. Query results unlock with a pass.
About the 3D CAD Viewer (STL, OBJ, 3MF, glTF, PLY)
Open a 3D model — STL (binary or text), OBJ, PLY, 3MF, glTF or GLB — on your device and look at it from every side, in perspective or orthographic views. Cut it with a section plane across X, Y or Z to see inside, with the cut faces coloured and the section area worked out; click two points to measure between them, snapping to the corners of the faces you hit.
The report gives the bounding-box size, the number of triangles and parts, and whether the mesh is watertight (no open or non-manifold edges) — the first check before 3D printing. For a closed mesh it adds the surface area, volume, mass for a chosen material (metals, and PLA, PETG, ABS and nylon for printing), the centre of mass and the principal moments of inertia. Files stay on your device; nothing is uploaded.
Without a pass, the free preview shows your model with a watermark, its size, counts and watertight check, and the values of the first half of your measurements; area, volume, mass, centre, inertia and section area, Copy report, the CSV and the PNG of the view come with a Pro pass.
How to use it
- Choose or drop one or more model files (for a .gltf with a separate .bin, choose both), or try the sample part.
- Drag to turn the model, right-drag or Shift-drag to pan, scroll or pinch to zoom; switch between 3D, Top, Front and Side, and orthographic or perspective views.
- If the size looks wrong, set Numbers in the file are (STL, OBJ and PLY store no unit; a model drawn in inches comes out 25.4 times too small in millimetres). Choose the material for the mass.
- Press Section, pick the axis and slide the plane through the model; Flip shows the other side. Press Measure and click two points for a distance with its ΔX, ΔY and ΔZ.
- Copy the report, download it as a CSV, or the view as a PNG — with a Pro pass, or after unlocking this result.
Examples
Ø40 × 5 mm flange, Ø24 body 25 mm long, Ø12 bore, as a 96-sided STL
Size 40 × 40 × 30 mm, watertight; volume 14.19 cm³ (the round part would be 14.20 cm³), about 111 g in steel at 7,850 kg/m³
Section across Z at 2.5 mm
An annulus of 1,142.7 mm² — π(20² − 6²) is 1,143.5 mm²; the 96-sided mesh is 0.07 % smaller
A 1-inch cube saved as STL without units, read as millimetres
Size 1 × 1 × 1 mm: set “Numbers in the file are” to inches and it becomes 25.4 mm (1 in) on each side
Common uses
- Checking an STL before 3D printing: size, holes in the surface, weight of filament it will need
- Weighing a machined or cast part from its model, in steel, aluminium, brass or titanium
- Measuring a model someone sent you, or cutting it open to see its walls and wall thickness
- Getting the centre of mass and inertia of a part for a quick dynamics or balance estimate
How volume, mass and inertia are worked out
For a closed mesh whose triangles face outward, every triangle and a reference point make a tetrahedron with a signed volume of ((a − o) · ((b − o) × (c − o))) ÷ 6; the sum over the surface is the enclosed volume (the divergence theorem). The same tetrahedra give the centre of volume and the second moments, ∫ x xᵀ dV = V/20 · (Σ vᵢvᵢᵀ + s sᵀ) for each tetrahedron with one corner at the reference point; moved to the centre of mass and multiplied by the density, they are the inertia tensor, whose eigenvalues are the principal moments. The section area adds up the cut segments of every triangle the plane crosses, oriented round the material, so holes are subtracted.
Formats
- STL: binary and ASCII, the format of most 3D printing; no units, no colours.
- OBJ and PLY: meshes with optional vertex colours; no units.
- 3MF: the 3D printing format with units, several objects and build items (3MF specification).
- glTF / GLB: the open 3D scene format, in metres and Y-up by definition, turned Z-up here (glTF 2.0 specification).
STEP and IGES describe exact CAD surfaces rather than triangles, and this viewer does not read them: export the part from your CAD program as STL, 3MF or glTF first (with a fine tessellation, the volume and mass are then within a fraction of a percent).
Limitations
- Meshes only: STEP, IGES, BREP and native CAD files (SolidWorks, Inventor, Fusion) are not opened; export STL, 3MF or glTF from them.
- Volume, mass, centre and inertia need a closed (watertight) mesh with consistent triangle directions; an open mesh shows its open edges instead.
- A mesh approximates curved surfaces with flat triangles, so curved parts measure slightly smaller than the exact solid; finer exports are closer.
- Textures and materials of glTF and OBJ files are not shown; vertex colours are.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
What do I get without a pass?
Without a pass, 3D CAD Viewer (STL, OBJ, 3MF, glTF, PLY) shows your model with a MySmartCoPilot watermark, its size, counts and watertight check, the first half of your measurements (up to 10); volume and mass are hidden. Until you unlock it, the result can’t be downloaded or copied. A Pro, Premium or Ultimate pass, a one-time payment that never renews, unlocks the full result. The pricing page lists the passes and their prices.
How do I find the volume of an STL file?
Open it here: if the mesh is watertight, the report gives its volume (and surface area). STL files store no unit, so check that the size matches what you expect, and set the unit if it is out by 25.4 (inches) or 10 (centimetres).
How much will my 3D print or part weigh?
Choose the material — PLA, PETG, ABS and nylon for printing, or a metal — and read the mass: volume × density. A print with infill weighs less than its solid volume; slicers report the filament for the infill you choose.
What does watertight mean?
Every edge of the mesh is shared by exactly two triangles, so the surface is closed with no holes or stray faces. Slicers need it to know what is inside, and it is required for the volume. The report counts the open and non-manifold edges when it is not.
Can I open STEP or IGES files?
Not in this viewer. STEP and IGES store exact surfaces that need a CAD kernel to turn into triangles. Export STL, 3MF or glTF from your CAD program and open that.
Are my files uploaded?
No. The models are read and drawn by your browser on your device, and the page keeps working offline once it has loaded.