Reflections on 3D scanning
By Matt Faber on Tuesday 01 April 2014 Tweet this!
Issues surrounding the rendering of highlights in 3D digitisation
Image by UCL (used with permissions)
As more and more 3D digitisation projects are conceived and initiated everyone involved becomes increasingly aware of the pros and cons of the various 3D digitisation methods. One of the really big issues that currently have people vexed is the rendition of specular and non-specular highlights on reflective and transparent objects. This has, since 3D digitisation became a reality, always been a major drawback and it is not until now that technology is starting to address this issue.
The three predominant methods of 3D digitisation are laser scanning, or time of flight scanning, structured light scanning and photogrammetry. Any scanning method which utilises a light source, be it incandescent or laser, is going to produce highlights which in turn are going to confuse the sensor and create issues when texturising. As software develops and becomes more adept at texturising it will ultimately be able to overcome these problems however it has to be recognised that in doing so one will be creating a false image i.e. the detail will not be rendered during capture but will be created in post-production.
With photogrammetry the issue is with the dynamic range of the camera sensor which currently still do not have the range to capture specular highlight detail. Obviously, sensor technology is advancing at a pace and it too will, no doubt, arrive at the point where highlight rendering is no longer an issue.
There have recently been several projects that have tried to address these issues and what’s interesting is that they have all used laser or time of flight technology. The Sheffield Hallam University project, which is funded by Jisc, has created over 200 3D images of Sheffield metalwork.
This project has proven highly successful and used state of the art laser scanning technology from Faro.
Also, UCL has been working in conjunction with the Petrie Museum to create 3D laser scans of ancient Egyptian artefacts.
UCL have been working with an Arius 3D scanner producing some exceptional results. The Arius is a full colour 3D laser scanner which, as such, requires no texturing.
The jury is still out with regards to the results but they are nonetheless impressive. What is interesting though is the debate surrounding the problems of highlight rendition, currently running, which hopefully will help future projects and add to the community’s better understanding.
Do take some time to have a look at the new Jisc Digital Media infokit on digital 3D content.
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