The requirements for taking photos in a project with curves is similar to the edge and cylinder description above but because a curve is not a straight segment, it can be both horizontal and vertical. This can make the photography more challenging.
You need both vertically separated photos and horizontally separated ones and the curve has to be marked and referenced on all of these photos. It is similar to the vertical and horizontal pipes example above. Imagine we had a circle curve, two ‘straight-ish’ curves and a complex curve on a plane. What photos would give good angles for all parts of all curves?
Curves 2 and 4 are close to being straight and require only two photos to model them well. Curve 2 is captured well by photos B and D and curve 4 is captured well by photos A and C.
Curves 1 and 3 have sections that point in all compass directions. For the circle 3, you might be able to mark and reference on just two photos but there will be areas that are not solved and only the circle fitting will overcome the deficiencies. Curve 1 is not fitted and if you were to use just photos B and D the parts shown below in red would not solve (and this may mean the end of the curve is missing or most is missing depending on which end the curves ‘starts’ at (where the shared referenced point is).
If all four photos are marked with curve 1 then it should solve completely.