Trnio’s Tutorial for Spray Coating Reflective Objects
Reflective objects don’t do so well when it comes to 3D scanning and Photogrammetry. This is because while you are walking around your object, scanning with Trnio, the light that reflects off of a shiny object will move, obstructing the photo matching process that creates your 3D model. We did some tests to see what the best method is for coating and mattifying reflective objects in order to produce more detail and a better scan.
The best method we have found is spray-on dry shampoo. We found that this was the best way to mattify your reflective objects because it is cheap, doesn’t ruin or stain your object, and has easy application and clean-up. The dry shampoo that we used is linked here: https://www.dove.com/us/en/hair-care/dry-shampoo/unscented-dry-shampoo.html
We chose this specific item because it has no scent, and leaves a white, filmy residue when a few coats are applied. One very important thing to remember is to let the spray dry before you scan your object! This should only take a few minutes. If you do not let all of the coats dry beforehand, the wet spray will be just as reflective as the surface.
We really wanted to put this product to the test, so we used the most reflective object you can find: a mirror. Usually a mirror will never be a successful scan, because there will be almost no points that match up since the entire object is reflected. For this test, I used a two-sided, small bathroom mirror in order to compare the results of dry shampoo spray vs. no spray in the same scan. Here are the results:
With Dry Shampoo:
Without Dry Shampoo:
As you can see, the side with dry shampoo spray had plenty of detail in order to match up the photos and create a complete scan. On the other side with no spray, however, there were no points to match, so the entire side is completely missing.
In another, more realistic test, we took a small model of a pink convertible. The car was made from ceramic with a shiny finish. Although this was not as reflective as the mirror, it still had a surface that would reflect light as it was being scanned. The dry shampoo spray worked very well for this scan:
With Dry Shampoo:
Without Dry Shampoo:
As you can see, there is also less white residue on the surface, because the car already had a color for the spray to lay on top of and sort of blend into. This spray is also very easy to clean - just wipe it off with a wet paper towel after scanning!
We hope this helps those of you who hope to scan reflective objects, and feel free to reach out with other scanning tests you’d like to see!