Practical 3D Scanning: Troublesome Surfaces & Objects
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Troublesome Surfaces & Objects
03.48
| 00:00 | Issues with the scanning process have been mentioned a few times in the previous modules, and while these can be influenced by the scanner, the software and how they're used, the primary cause of issues are more often than not the subject of the scan itself. |
| 00:15 | Most scanners will struggle with reflective and transparent surfaces, like glass or polished metals, especially if they're a dark colour. |
| 00:24 | In short, this is due to how the light from the scanner's projector interacts with the surface it lands on. |
| 00:29 | As we've discussed already, the scanner's cameras are sensitive to this and any discrepancies can cause issues in the data collection. |
| 00:39 | Structured light scanners do tend to struggle more than laser scanners here due to the intensity and wavelength of the light. |
| 00:46 | This is also why blue light sources generally work better than white light sources in these cases. |
| 00:52 | To help, matting sprays are available and can be sprayed onto these surfaces to create a very thin layer with a matte finish and lighter appearance, essentially creating a nice opaque surface and making it easier for the scanner to collect data. |
| 01:08 | These sprays are formulated to not damage the components they're being sprayed onto and some are also designed to vanish, meaning they evaporate from the surface after a certain amount of time, while others remain on the surface and need to be cleaned off. |
| 01:23 | As you'd expect, this can cover the actual appearance of the object like we discussed for our positioning targets, which will be a problem if we want to capture this data. |
| 01:33 | So, in this case we need to get a transparent option. |
| 01:36 | Although extremely effective, dedicated matting sprays are expensive. |
| 01:41 | Thankfully though there are some alternatives. |
| 01:44 | It can be helpful to apply an easily removable product like car wax, plasti dip or even novelty colour hairspray to temporarily remove the gloss finish without affecting the surface shape. |
| 01:56 | Even mixtures of baby powder diluted with water in a spray bottle can be effective, though this does require much more cleanup process and we obviously need to be careful on what we spray them onto as they can be damaging. |
| 02:10 | The other common troublesome object issue is closely related to the tracking and positioning discussion covered in the previous module. |
| 02:18 | As we discussed, objects with minimal geometry or texture features can make it difficult for the scanner software to understand its position and the shape of the target. |
| 02:29 | Take the door of a vehicle for example, there will likely be a very plain section of geometry with a slight curve, but no real distinguishable geometric features within the field of view of the scanner. |
| 02:40 | This makes it difficult for the scanner to track its movement as one section of the door will appear the same as another. |
| 02:47 | That doesn't mean that we still can't have problems with scanning objects with lots of features. |
| 02:52 | Repetitive geometry can cause a very similar issue where the scanner sees what it thinks is the same section of the part and creates an incorrect model. |
| 03:02 | A transmission gear would be a good example of this. |
| 03:05 | In this case, adding positioning targets to the object will allow the scanner and software to distinguish the different parts of the geometry and build a correct model. |
| 03:15 | With that covered, let's look at the key takeaways from this module. |
| 03:19 | If working with highly reflective or translucent objects, particularly those of dark colours, matting sprays help create a scannable surface and can vanish, avoiding any need for clean up. |
| 03:30 | These tend to be expensive, but there are some other cheaper alternatives. |
| 03:35 | Objects with minimal features or very repetitive features can also cause issues with positioning, so in these cases we need to add texture or use positioning targets. |
