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Why is my 3D model completely white when the recipient opens it?

Because the geometry made the trip but the appearance didn't: OBJ keeps colour in a separate MTL file, and STL can't carry colour at all.

The three reasons a 3D model arrives without colour

There are essentially only three explanations, and they can be told apart in a few seconds.

1. The format can't carry colour. STL contains nothing but triangles — no colour, no materials, no textures. An STL that arrives white isn't broken; it's simply behaving the way STL always does. If the recipient needs to see colour, the file has to be a different format.

2. The side files are missing. OBJ stores the geometry in the .obj file and the appearance in an .mtl file next to it. If the materials reference images (textures), those live in yet more files again. Attach only the .obj file to an email and the house arrives — but not the colour. The same applies to the shared form of glTF (.gltf plus a .bin plus images).

3. The model never had colour to begin with. A building model built from a measured floor plan is geometry: walls, floors, doors, windows, furniture. Whether materials were ever applied depends on what gets exported. In HouseSense, only USDZ carries the appearance of materials along with it — the other model formats hold the shape, not the surface.

How to work out which of the three it is

1. Check the file extension. If it's .stl, the matter is settled: the format simply can't do more.
2. Look in the folder. Is there an .mtl file sitting next to the .obj file? Are there .png or .jpg files? If so, the problem is that they didn't make it into the shipment.
3. Open the same file yourself. If it's white on your end and the recipient's, the model never had colour — so it isn't a delivery problem.

The fix: send one format that stands on its own

The robust route is to send a format where everything sits in a single file, so there's nothing left to lose along the way:

• GLB — glTF packaged as one binary file. Geometry, materials and textures all inside. Opens in browsers, Blender, Unity and most 3D viewers. The best default choice when the recipient is on Windows or the web.
• USDZ — Apple's format, also a single file with the appearance built in. Opens directly in Messages, Mail, Files and Safari on iPhone, iPad and Mac, and can be placed in AR. The best choice when the recipient is on Apple hardware.

If it really has to be OBJ — because the recipient asked for it, or because the software is old — then zip the whole folder and send the zip file. Not the .obj file on its own. Tell the recipient in the email that the MTL file needs to stay in the same folder as the OBJ file once it's unzipped; that's usually where things go wrong at the other end.

PLY, colour per point, and viewers that ignore it

PLY is a special case. PLY can carry a colour per vertex — not as a texture, but as a colour value attached to every point in the model. This is the usual way scanned data and point clouds carry colour.

The catch is that not every viewer draws vertex colours by default. CloudCompare and MeshLab do, but many ordinary 3D viewers look for a material, find none, and render everything grey. The recipient has to switch on vertex colours — or use a different format.

If colour is what matters, send GLB or USDZ. If the measurements are what matter, send PLY and mention in the email that the colour sits per point.

White isn't always a fault

It's worth holding onto the fact that a white model is often exactly what's needed. An architect who needs to measure the geometry doesn't care whether the walls are beige. A 3D printer can't use the colour anyway. And a white model opens faster and takes up less space.

So the question isn't "why is it white" but "what does the recipient need to do with it":

• Does the recipient need to see what the home looks like — send USDZ or GLB.
• Does the recipient need to measure and keep drawing — colour is irrelevant. Send whichever format the software on the other end reads — and if the next step is a 2D drawing, the answer isn't a 3D model at all, it's a DXF.
• Does the recipient need to print it — send STL, and don't worry about colour.

What a home model shows — and what it never does

A 3D model built from a measured floor plan is a building model: the shape of the rooms, the position of the walls, doors, windows and ceilings. It isn't a photograph of your home. The wallpaper pattern, the sofa's upholstery and the scratch in the door frame aren't there — not even in the format that carries materials.

It's worth saying this to the recipient, because the expectation is often different. A model that arrives white or single-coloured looks like a broken photograph, but it is a to-scale description of the home's shape. The shape is what makes it useful.

And one last thing that no colour changes: a 3D model can never tell you whether a wall is load-bearing. That question needs a building surveyor or a structural engineer — no matter how real the model looks.