machine learning are modifying prosthetics

Although 3D scanning and photogrammetry aim to produce a 3D model of an object/human/environment, the technologies used behind are completely different.

Photogrammetry is the process of making measurements from photographs. Photogrammetry works by capturing multiple overlapping digital photographs from different angles which are then digitally reconstructed into 3D models by computational algorithms. Realistic and accurate surface texture is achieved through an overlay of the original photos onto the 3D mesh. In summary, the input is multiple digital photos from different locations of an object and the output is a 3D mesh of the object.

In 3D scanning, the shape of an object is captured by a 3D scanning device recording millions of data points to create a dense vector point cloud. Many different 3D scanning technologies exist (structured light, infrared structured light, laser, etc) and each of them have its own limitations, advantages, and costs (more detail in a next post). Some 3D scanners can also collect the texture (color) of the objects in addition to the shape.

Both have their pros and cons and the best solution is user-dependent according to their needs, usage, and budget.

Equipment and cost

Photogrammetry

  • Camera + post-processing software
  • Starting from 0$ with freeware (if the accuracy is not important for you) to over 10k$
  • Better quality with a professional camera and commercial software (from 179$ to over 2500$)

3D scanning

  • 3D scanner + software (capture and post-processing)
  • Price from 1k$ to over 25k$ depending on the quality you need
  • Becoming more and more affordable and smartphones might soon have the capability to do 3D scan with Time-of-Flight camera (more details in a next post)

Model/Environment

Photogrammetry

  • Object/Human body/other
  • Issues with reflective, shiny, featureless and smooth surfaces and repetitive pattern
  • Everywhere with light

3D scanning

  • Object/Human body/other
  • Issues depending of the technology used
  • No needs for special environmental condition
  • Some scanners cannot scan under natural light, some other cannot scan with the metallic environment, the limitation is often dictated by the technology used

Accuracy/Visual quality

Photogrammetry

  • Accuracy depending on different factors: camera resolution, software, angles, distance, number of pictures
  • Better texture quality
  • Approximative scaling, depending on the solution

3D scanning

  • Very accurate: from 2mm to under 0.25mm for high-level 3D scanner
  • Texture limited because of the camera used
  • Scaled by default

User experience/Time

Photogrammetry

  • Need experience for taking optimal pictures for computer algorithms and for post-processing
  • No real-time preview of the 3D mesh
  • Slow recording: from 2 to 5 minutes (depending on the number of pictures)

3D scanning

  • Easy to make a scan because it only requires little technical knowledge
  • Real-time preview of the 3D mesh on the screen
  • Fast recording: < 2 minutes
  • Fast post-processing: < 5 minutes

In summary, photogrammetry is cheaper and leads to good visual quality 3D model while 3D scanning is more expensive but have better accuracy and is easier and faster to use. For now, 3D scanning seems to be the best solution to record 3D human body in a context where time and easy-use are the most important factors. The best solution for you is always depending on your need for accuracy.

Sources:

https://www.collinsdictionary.com/dictionary/english/photogrammetry

https://www.aniwaa.com/3d-scanning-technologies-and-the-3d-scanning-process/

https://matterandform.net/blog/the-hardest-objects-to-scan-paths-to-success

https://www.tested.com/art/makers/460142-art-photogrammetry-how-take-your-photos/

Dixit I., Kennedy S., Piemontesi J., Kennedy B., Krebs C. (2019) Which Tool Is Best: 3D Scanning or Photogrammetry – It Depends on the Task. In: Rea P. (eds) Biomedical Visualisation. Advances in Experimental Medicine and Biology, vol 1120. Springer, Cham

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