Photographing an object for 3D reconstruction

The camera work that decides how good a reconstruction can be. Mostly lighting, background and angle.

Reconstruction quality is set by the photograph before any software runs. Most bad results are bad inputs.

Lighting

Even and diffuse. An overcast day, a north-facing window, or a softbox. The goal is to see the object's shape without hard shadows.

Hard shadows are the main enemy, because a shadow is a dark shape and reconstruction reads dark shapes as form. A crease of shadow under a chair seat can reconstruct as an actual crease in the geometry.

Avoid direct sun, single bare bulbs, and on-camera flash — all produce exactly the harsh contrast that causes this.

Background

Plain, and contrasting with the object. A white object on a white table has no findable silhouette; a white object on mid-grey does.

Avoid patterns, strong lines and anything with its own visible edges. If you can, shoot on a sweep so there is no horizon line where the surface meets the wall.

Angle

Three-quarter beats straight on. A front-on photograph shows one face and almost no depth information. Turning the object thirty to forty-five degrees reveals two faces and their relationship, which is far more for the reconstructor to work with.

Slightly above is usually better than eye level for objects that sit on a surface.

Lens and distance

Stand back and zoom in rather than moving close with a wide lens. Wide angles at close range distort proportions, and the mesh inherits the distortion faithfully.

Focus and exposure

Everything sharp. Use a smaller aperture for depth of field, and a tripod if the light is low. Blur removes the detail reconstruction reads.

Expose so highlights are not blown out — a blown highlight is a region with no information at all.

Things that will not work

Transparent, highly reflective, very dark or very fine-detailed objects. What the camera records is not the surface, and no amount of care fixes that. Matte-spraying a reflective object is a real technique if you can do it.

Multiple views

If you are supplying several views for multi-view reconstruction, rotate the object and leave the camera fixed. Moving the camera changes perspective between shots; rotating the object does not.