3D Model of Bison Thoracic Vertebrae
Animal bones are an archaeological material which are important to understand the past. They provide information of cultural and natural history or prehistory and hints to reflect the migration of the animals, the living habits of humans or climate changes in that area. Besides, archaeological materials are able to give a lot of information which work associating with other studies, such as anthropology, ethnography, geology, paleontology, biology, etc. Therefore, the protection of archaeological information, including animal bones, is important.
This project is an exercise to create a 3D model for a small object. 3D modeling an archaeological material is beneficial to researches, information sharing and education. Figure 1 is a Bison bison thoracic vertebrae from a modern bison used in a comparative collection to identify thoracic vertabrae from archaeological contexts.
Preparation and Method
The process of 3D modeling a small object is similar to 3D modeling larger objects such as a Giant Pampathere I did at the Lubbock Lake Landmark. The first is to gather images of the subject of interest. Then, images would be imported into Agisoft PhotoScan to render a 3D model. Different from outdoor objects, the image gathering can be done indoor which means sunlight, climate and geographic factor are no longer an issue in this case.
The images for this project are taken in the 3D printing room at the Museum of Texas Tech University. The advantage of taking photos in an indoor studio is that we could have control of the light sources. It would not be affected by weather, sunlight direction, and time.
For the preparation of equipment, light tent, light source, DSRL 7100 Nikon camera and tripod are needed for better images. The object of interest would be placed in the light tent. The translucent sides of the light tent are able to diffuse the light coming from the light sources. It is an effective way to avoid shadow in the images. A tripod is able to stabilize the camera from an angle which you have taken. A DSRL camera with a fixed lens insures quality of all images is equal. Correct settings in aperture, ISO and shutter speed are also necessary for better images.
Due to the odd shape of the bone, 40 images have been taken for gathering enough information for photoscanning. The most difficult part of the whole process is to take images of the holes on the bone. 8 extra photos have been taken dedicatedly for the information of the holes. Figures 3 and 4 are the images of the holes.
To improve the quality of the end product, images needed to be edited by Photoshop. The DSRL is able to take photos in RAW format which has better quality and record the information of settings. However, TIFF is handier in terms of image editing with Photoshop. Therefore, the first step is to convert all images from RAW to TIFF (Figure 5).
The other way to improve the quality of the 3D model is to remove the background of the object in the image. Select tool helps to select the object in the image and build a mask on it (Figure 6).
Once all images are ready, they can be imported into the Agisoft PhotoScan to process the rendering. Here is the setting (Figures 7–10) of each workflow for this project:
All in all, the result of the 3D modeling is just acceptable (Figure 11). The shape and the texture of the object are able to be reproduced in the 3D model. However, there are two main problems of the 3D Model. First, there are some unexpected white chunks somehow rendered in the model. I tried to photoscan again but the results look the same. The second issue is that the deep, inner area of the holes is failed to be rendered. There are few hollows on the sides of the bone. The potential reason is that the images do not entirely cover the information of that area.
In conclusion, gathering images in an indoor studio is easier and more convenient than an outdoor please. We can have a better control of light source which provide images with high quality. Also, a small object is easier to be managed. I can flap over the small object for taking photos of different angles which helps to create a complete 3D model. To solve the problem of the hollows, more details of the holes has to be covered. For the white chunks of the 3D model, more tries and further study are needed to figure out the problem.