What is 3D-scanning (photogrammetry)?
It’s a technique of creating 3D models without actually modeling objects from scratch. It was developed and improved not long ago – comparing to traditional 3D modeling.
Making long (and much more complicated) story short: the algorithm processes many pictures of the same object comparing them and finding similarities. Basing on this, it finds small differences in the position of points – this way it can recreate camera angle and distance of every picture taken. Finally, the algorithm can create a 3-dimensional point cloud of the object and recreate the shape and color of photographed object – giving us what we need: UV-mapped mesh and diffuse map.
Why scan?
Photogrammetry brings unprecedented quality to the table. It solves some very painful issues you have to face when modeling and texturing the traditional way: keeping real proportions, adding details to mesh, matching texture with mesh, taking care of good texture stitching on seams. It also gives you awesome texture quality and resolution – limited only by your hardware specs.
Another great advantage is the ability of 3D modeling without actually building your mesh from scratch. Photogrammetry software gives you a highly detailed mesh. Then you can process it your own way: simplify, remesh, create new UV map, whatever.
In brief, you get realism and quality like never before.
Limits
The biggest curse of this method is that you have to have an object to scan 😉 And the ability to take pictures from every side/angle.
This technique doesn’t work on every object. Forget about shiny metals, glass, water, etc. The rule is that object has to look the same way from every angle; no reflections acceptable here. Also, the object cannot deform or move while taking pictures. So if you want to scan an ice cream or a human, make sure to take all the pictures before your object melts or moves. The model complication level is limited only by your hardware capacity. But think twice before trying to scan a tree with thousands of leaves. On the other hand – too simple, geometrical objects (especially smooth with plain color) are better to model traditionally.
If you want to have a proper color map, you also have to take good care of lighting; no sharp light and shadows allowed here.
We’ll deal with all this in the next parts of this article.
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