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+categories = ["software"]
+tags = ["photogrammetry"]
+date = 2025-07-02T20:00:00-05:00
+description = ""
+draft = false
+slug = "photogrammetry"
+title = "🗿 Photogrammetry - Tongan Wood Carving"
+author = "nicholas"
+++
+
+I was gifted a beautiful yet somewhat haunting, grimacing figure, carved of wood, which I am told was gifted to one of my great uncles by the king of Tonga himself. I do know quite what to do with this object besides to proudly display it on a small table by the front door of my apartment. But what if I lost it? What if it just vanished? As its new caretaker, I figured it would be prudent to digitally preserve this artifact. After all, if I take seriously the [dubious claimed provenance](#-god-figure) of the item, I am dealing with the once-property of a king!
+
+
+## 🚁 Drone Mapping
+In the past I would fly drones around my hometown and make 3D models and ultra-high-res aerial maps using a RC quad-copter (*DJI Phantom 4 Standard*). This was before the FAA implemented *14 CFR Part 107*, which frankly sucked the fun out of flying the drone. I sold it a few years of disuse. Many years later I have returned to this technology, but this time I will use a conventional camera (*Nikon Z50*) instead of a drone-mounted camera. Same principle, though.
+
+For example, here is a 3D model of the courthouse in my hometown that I created.
+
+{{< modelviewer
+    src="models/courthouse.glb"
+    alt="3D Model of courthouse" >}}
+
+## 📷 Image Capture
+
+To capture good images for the totem 3D model, I will need good lighting. I use the natural sunlight from the gigantic sliding plexi-glass door to the deck to illuminate the object. I also use the two [plant grow lights]({{< relref "posts/grow-lights" >}}), adjusting their angles. This gives me plenty of light to capture the images at low ISO and narrow aperture, which are necessary to obtain high quality, high depth of field images. The latter allows me to have all of the elements of the totem mostly in focus without focus-stacking. 
+
+**Turntable:**
+I use *Ateco 12" Cake Decorating Stand* as my turn-table, and an unfortunately very heavily linted cloth napkin over the top, to avoid capturing the reflective finish of the aluminum. 
+
+**Background:**
+The backdrop is a black blanket draped over the coffee table.
+
+**Camera Settings:**
+ - **Camera:** Nikon Z50 
+ - **Lens:** NIKKOR Z DX 16-50mm
+ - **ISO:** 100
+ - **Aperture:** f/8
+ - **Shutter Speed:** 1/8s
+ - **Focal Length:** 35mm
+
+I also use the **Time-lapse sequence** feature to automatically capture one frame every 4 seconds. This allows me to spin the turntable ~10° between each shot (I aim to capture ~40 images). 
+
+**Angles, Positions, Framing, Focus**
+- Center the item on the turntable
+- Position camera at a height such that subject is ~30° below
+- Distance the tripod so that totem occupies much of the frame
+- **Manual** shooting mode and focus to keep images consistent
+
+Here is a sample photo that gets turned into a 3D object.
+
+{{< image 
+src="images/totem-on-turntable.JPG" 
+caption="Totem on turntable" >}}
+
+As one can see from the photo, there is much room for improvement, e.g.
+- Cleaner, Vanta black background
+- Shadowless lighting
+- Greater depth of field
+- Reduce shininess of model
+
+
+My capture setup is clumsy and ad-hoc, but it worked for my purpose.
+
+---
+
+## 🖼️ Image Processing
+After I capture the photos, I process them in a couple of places.
+
+- **Agisoft Metashape**
+    - align photos
+    - build point cloud
+    - build model
+    - build textures
+    - export `.obj`
+
+This results in a complete model with textures. However, if I want to edit the model, or to convert it to a different format (`.glb`), or animate it, I use Blender. There is a lot of things I *could* do at this stage to refine and improve my model, but a quick and dirty model is all I want. The pareto principle, law of diminishing returns seems to apply here.
+
+Here I use Blender to animate my model spinning around.
+
+- **Blender**
+    - import `.obj`
+    - position camera
+    - add lighting
+    - add animation keyframes
+    - adjust output settings (resolution, FPS, etc.)
+    - render animation frames
+
+{{< image 
+src="images/totem-blender-animation.png" 
+caption="Exporting frames in Blender" >}}
+
+According to the selected options, after this last step I now have a a series of frames that I can make into a video with `ffmpeg`. In the examples below, I am creating `.webp` images.
+
+
+**60fps, 80 quality, 480p**
+```shell
+ ffmpeg -framerate 60 -i %04d.png -vf "scale=480:-1" -vcodec libwebp_anim -q:v 80 -loop 0 -pix_fmt yuva420p tonga-60fps-80q-480p.webp
+```
+**lossless**
+```shell
+ ffmpeg -framerate 60 -i %04d.png -vcodec libwebp_anim -lossless 1 -loop 0 -pix_fmt yuva420p tonga-60fps-lossless-1920p.webp
+```
+
+## 📦 Results
+{{< image 
+    src="images/tonga-60fps-80q-480p.webp"
+    caption="WEBP image/video" >}}
+
+
+{{< modelviewer
+    src="models/tonga.glb"
+    poster="images/tonga-60fps-80q-480p.webp"
+    alt="tonga" >}}
+
+I also scanned a randomly selected book.
+
+{{< modelviewer
+    src="models/book.glb"
+    alt="Book" >}}
+
+Done.
+
+## 🗿 God Figure
+> Source: [Museum of New Zealand](https://collections.tepapa.govt.nz/object/1314394?page=1&rtp=1&ros=1&asr=1&assoc=all&mb=o)
+
+{{< image 
+    src="images/god-figure-carving-museum-website.png"
+    caption="God figure page from the website" >}}
+
+ ### Overview
+
+This is a wood carving made in Tonga in 1983. It is small and portable and made from a light timber with a dark grain. It is one of several carved figures in the Pacific Cultures Collection made for the tourist market in Tonga in the mid to late twentieth century.
+
+**Significance**
+
+In the 1800s, wood carving was a well-established art form in Tonga. By the mid-1900s, it had diminished as the religious and customary contexts for its production had radically changed. In the 1960s and 1970s, visiting cruise ships to Nukualofa were a major market for handicrafts and curios. Tourism to Tonga stimulated a revival of wood carving in a range of mainly non-indigenous forms. In 1984, Kernot noted that these included Hawaiian style temple figures, generalised "Polynesian" figures, mermaid and warrior figures.
+
+**A Pan-Pacific Style**
+
+This particular figure fits within a carving style that anthropologist Philip Dark described as *Pan-Pacific*. These carvings emphasised a "grimacing mouth", which would appear to have its origins in Hawaiian carvings, such as those of the atua (god) Kuka’ilimoku. Similar composite works typical of the time feature Tahitian style blended with Marquesan forms. Hawaiian style carvings and pseudo-Marquesan tiki had been carved and sold in Samoa since 1965 and in Tonga by at least the 1970s (Dark 1990:258).
+
+A Tongan handicraft guide published in 1980 states:
+
+> "The carvings in Tonga have a chunky, stolid power about them that says clearly that they come from the South Pacific. Although those for sale are not sacred images, many are reminiscent of such ancient origins… Although many of the pieces they carve follow traditional designs, many carvers have their own specialities. One may see carvings of splendid dragons and many varieties of tiki, the Polynesian god image… But some of the better carvers concentrate on making excellent copies of intricately incised wooden linen chests and lampstands… for which there is a market"  
+> *(anon. 1980:21-22)*
+
+Although these items were examples of the skills of Tongan artists as wood carvers, they were not part of any previously documented tradition of woodcarving in those islands.
+
+**Acquisition History**
+
+This carving is part of a larger group of items collected by Bernie Kernot in 1983–1984 while on university sabbatical to Tonga, Fiji and Samoa. The carved items are from the workshop of Nau in Nukualofa. At this time, he was also on the executive of the Pacific Arts Association (PAA) and while on this trip he publicised the PAA among Pacific academics and artists. Kernot was a senior lecturer in anthropology and Maori Studies at Victoria University, Wellington, New Zealand between 1967 and 1996. He published widely on Maori sociology, politics, art and religion.
+
+**References**
+
+- Dark, Philip J.C. 1990. *Tomorrow’s Heritage is Today’s Art, and Yesteryear’s Identity*. In Hanson, Allan and Louise Hanson (eds), *Art and Identity in Oceania*. Bathurst: Crawford House Press, pp. 244–268.  
+- Kernot, Bernie, 1984. *Tonga* (unpublished field notes). Te Papa File.  
+- (Anonymous) 1980. *Tongan Handicrafts*. Canberra: Australian Government Publishing Service.