Tip 51: Creating Lofted Surfaces in Photogrammetry

Tip 51 Screen ShotPhotoModeler has the ability to create NURBS-based curves and surfaces. NURBS are Non-Uniform Rational B-Splines. These are a power mathematical definition for curves and curved surfaces used by many top-end CAD packages.

In the case of photogrammetry the data that supports the curves (3d points or 2d curve profiles) are created from the photo data. Then the NURBS curves and surfaces are fit to that underlying data.

In this tip we show the Loft tool. A Lofted surface is one that goes ‘through’ a series of curves (like the ribs on a boat hull).

The example is a car-top luggage box. It has a nice aerodynamic shape and if we want to recreate it with photogrammetry we can use a number of techniques. Since the object is very shiny and we want high accuracy we covered the box with strips of dot targets. These targets are automatically marked in PhotoModeler. Curves are then drawn though the strips of 3D targets. Lastly a Lofted surface is connected to the curves.

As with most PhotoModeler data, these curves and surfaces are parametric. That is, if an underlying point’s position changes (mark moved, reference deleted, project reprocessed) then the curves and the loft surface update automatically.

Watch the Youtube video to learn more.

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