Kuu3D is a 3D viewer for iPhone and iPad. It supports USDZ, OBJ, STL, glTF / GLB, PLY, and more. Open files directly from the Files app, AirDrop, or the Share sheet of other apps.
Which file types can I open?
Kuu3D supports USDZ / USD, OBJ, STL, glTF / GLB, and PLY (point clouds). You can open files from the Files app or from the Share menu in other apps. AirDrop is also supported.
Is there sample data?
On the screen with no model open, tap "Open Sample" to try a mesh (the Moon) or a point cloud (a trefoil knot). Samples aren't added to your library.
Files take a long time to open.
Large models take longer to load and prepare for display. The elapsed time is shown, so please wait until the model appears. OBJ is a text format and takes especially long. Converting the same shape to STL or GLB makes it much faster.
I can't open a large file.
If a file is too large for your device's memory, you'll see a confirmation message before it opens. As a rule of thumb, models over about 500MB (about 10 million triangles for STL) may not open. Reduce the polygon count in your 3D software or split the model before opening it.
The file is too heavy to open, or I want to make it lighter
The free web app "Sirppi3D Web" reduces the triangle count of a 3D file so it becomes lighter. Its "Match Kuu3D size" button sets the size Kuu3D opens smoothly. It runs entirely in your browser; your files are never uploaded.
The app quit when I opened a large file.
If your device runs out of memory, the app may quit. The next time you launch it, you'll be told the name of the file that was open. That file won't open automatically and no thumbnail will be created for it. Try again after making the model lighter.
I put a heavy file directly into the Kuu3D folder using the Files app.
The app may quit once, but it won't keep quitting repeatedly. The list reads only names and sizes, and no thumbnails are created for large files. A memory check appears when you open them. If the app quits while loading, you'll be notified at the next launch and the file won't open automatically.
Can I open .3mf or .fbx files?
Not supported in the current version.
The model looks inside out.
Some models have reversed face direction (normals). A confirmation message appears when you open them. Try toggling Z-up, or fix the model in other 3D software.
I want to change the dimension unit.
Tap the dimensions in the info bar to choose from mm, cm, m, or inches. Your choice is saved for each file.
Dimensions show "estimated."
The unit is detected automatically from the file format. Tap and choose the correct unit, and the "estimated" label disappears and your choice is saved.
I want to change the MatCap (material look).
Tap the MatCap button in the toolbar to switch between the 6 MatCaps and the silhouette view.
I want to change the background.
Use the background button in the toolbar to switch between 4 backgrounds: Sky, Dusk, Night, and Sakura.
I want to use wireframe.
Use the wireframe button in the toolbar to overlay the mesh lines. You can switch between 3 colors.
The model appears small and off to the edge of the screen.
Double-tap the screen to automatically fit the whole model in view.
I want to tilt the model.
Twist two fingers as if drawing a circle, and the model tilts around the viewing direction. Double-tap to return to the original orientation.
What is Z-up?
Different 3D software uses either Y or Z as the up axis. If the model looks like it's lying on its side, toggle the Z-up button in the toolbar.
I want to change the light direction.
Tap the light button in the toolbar and a white circle appears on the screen. Drag inside the circle to change the direction of the light. The small dot inside the circle shows the light's position. When the dot is filled white, the light is in front of the model (on the side you're viewing); when it's just an outline, the light is behind the model. The circle is always shown at the center of the model and fades away automatically if you don't use it. Tap the light button again to exit. The light direction is kept, and returns to the default position when you switch to a MatCap or wireframe.
The turntable stops partway.
In the free version, the turntable stops after a half turn (180°). Unlock All Features to keep it spinning.
The buttons disappeared during the turntable.
During the turntable (auto-rotate), the on-screen buttons hide automatically after about 2 seconds. Touch the screen to show them again; they hide again about 2 seconds after you lift your finger. You can turn this off in Settings.
I was told the library is limited to 3 items.
The free version can store up to 3 items in the library. Unlock All Features for unlimited storage. You can also delete existing items to import new ones in the free version.
What happens to my file when I import it into the library?
The file is copied to the Kuu3D folder. The original file stays where it is.
Library thumbnails don't appear.
Thumbnails aren't created for large files, to avoid running out of memory while generating them. Instead, the file size is shown below the file name and the format appears at the top right.
My library data disappeared after I changed devices.
Library data is stored on your device. Backup to iCloud isn't currently supported. Keep your important files as originals.
Model colors or textures aren't applied.
"Load Colors" in Settings is turned off. When it's on, models are displayed using their textures, vertex colors, and materials. Switching it automatically reloads the open model. Point cloud colors are always applied.
Is it a one-time purchase?
Yes, it's a one-time purchase (not a subscription). Buy it once and use it with no additional charges. Family Sharing isn't supported.
What do I get with Unlock All Features?
You can store unlimited items in the library and keep the turntable spinning. All other features are free to use.
My purchase disappeared after changing devices or reinstalling.
Tap "Restore Purchase" on the Settings screen. If you're using the same Apple ID, your purchase will be restored.
Do you collect personal information or my data?
No. We collect no data at all. Files you open are stored only on your device and are never sent anywhere. (Only the purchase process is handled by Apple's App Store.)
Can I play animations?
Not supported in the current version.
I want to save a screenshot.
The app has no screenshot feature. Use the built-in iOS method (side button + volume button).
Can I use it on iPad?
Yes. It works on both iPhone and iPad, and on iPad in both portrait and landscape.
Contact Support
If your question is not answered above, please reach us by email.
support.studio.yoru@gmail.com