Last week, we introduced you to the concept of photogrammetry--using a series of photo images to computationally map a 3D model or space. We discussed the current state of photogrammetry, including what software is available for consumers and what kind of hardware you need. Turns out, photogrammetry is pretty accessible, and you can do a lot even with free tools like Autodesk's 123D Catch and your smartphone camera. Of course, more advanced software, more processing power, and better camera equipment can go a long way to improving your models. But so can the simple act of taking better source photos. Today, I'm going to give you some tips about how to best take your photogrammetry photos to give that computing software the best references to output a clean(ish) 3D mesh.
By far, the biggest impact on the final output file is what happens in the shooting phase. In fact, it is usually easier to reshoot a new series of source photos of your subject then try to save a computed capture that’s not working right away. Take some time, think, try to visualize the computer aligning your photos. Try to think of angles you have missed. When you are done shooting, I recommend loading up the images and see how well the images align as soon as possible. If certain images are off or are confusing the software, re-shoot them while you still have access to your subject. It may be necessary to reshoot multiple times for one model.
Ideal Conditions for Photogrammetry Software
This part isn't too complicated. Your software will want a nice, clean, sharp, evenly lit image, with every surface of your subject visible from three or more angles. The software will also like a good amount of parallax (different positions and angles) between those images to do its calculation. And it'll really be happy if undesired parts of the image, not part of the subject, are masked off, either with a green screen or in an image editor.
Sounds simple, right? Well that's because it's easier to explain what photogrammetry software likes by giving you examples of what kind of imagery it doesn't like. That's because a lot of photography flourishes--depth of field, dramatic lighting, wide-angle distortion, etc.--are actually counter-productive to the task of photogrammetry. Below, I'll go in-depth through the image qualities that will confuse your software and produce bad models.