Sculpting the 3d models

After scanning the crown on Friday, we took a good look at the result.

Unfortunately, the original crown is quite old and some of the details have been worn off. The following image shows how the loss of details on the ornaments of the crown is clearly visible. Luckily, some sides have more detail than other sides and therefore we know what shape the details have and what we could do to improve them.

The visible loss of detail in the ring of the scanned crown

In addition to the loss of details, the existing paint layer is quite thick and due to the accuracy of the scanner, the lines where the paint was worn off are clearly visible. If the model is printed and cast without smoothening this, the lines will be visible on the cast iron, giving the final product an unwanted finish.

The cracks and paint lines are clearly visible on the model

On top of this, the original structure to mount the crown on the fence is still partially present. Three ‘feet’ were used to stick the crown to the concrete poles. After scanning, the three feet and a bit of concrete is still present in the model. These will have to be removed, since the new way to mount the crown is going to involve a different method.

In order to mount the crown, three feet were added and are still in the scan.

In order to get rid of the paint lines, mounting structure and bring back some of the details, we have a few options during the project. One of the options is to edit the 3D model. Another option would be to retouch the print of the model and depending on the method of casting, the wax can be retouched as well.

We decided to test how hard it would be to digitally retouch the model as this was the most accessible option to begin with. The only problem with this is that most 3d programs do not like the complexity of the model or cannot edit the ‘mesh’ this model consists of. Therefore, we had to search for a program that is able to sculpt 3d models to digitally edit the crown. The following is a list of the programs we used and why they did or did not work for us:

Slicer (Open source: https://www.slicer.org/)

After investigating in a project a few years ago, we read that this project used a CT scan to scan their objects. Using the images, they were able to create a model using Slicer. We hoped that this program also included some modelling options for pre-scanned items, but we were unable to find them.

Meshlab (Open source: http://www.meshlab.net/)

Meshlab is an interesting program for 3d models, since it includes a lot of different filters and options to edit, smoothen and finalise the model. Unfortunately, due to the unfriendly user-interface and the inability to undo actions, simple tasks, such as removing a bump were really difficult.

Geomagic (Wrap) (Trial version: http://www.geomagic.com/en/products/wrap/overview)

Geomagic is a professional program to create scans, edit them and improve models in general. Because this is a professional program, we could only use the trial version. After installing using the “Mesh Doctor”, the limitations appeared. All options were greyed out and you could not save the result.

SculptGL (Open Source: https://stephaneginier.com/sculptgl/)

This web based program was perfect for us. It allowed us to load the object and sculpt it like it is clay by adding, removing and smoothing material. Using this program, we were able to remove the mounts and make the paint layer smoother.

The image below compares the raw scanned crown with the retouch version from SculptGL. Left is before editing and right is after editing. The result is not perfect yet, but the more we can change in the model, the less we have to change once we have a printed version. Bringing back small details is really difficult in the model, so most of the refining has to be done at a later stage.

The comparison between the unaltered model (left) and the edited model (right)

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