Photogrammetry has incredible potential in archaeological research and education. However, despite Agisoft PhotoScan’s relatively simple initial workflow, things get complicated pretty quickly. Those of us using the program tend to learn by solving problems as they occur, but this is a very piecemeal, time-consuming, and often frustrating process. Currently, anyone getting started with the program must either go through the same thing, or find someone to offer guidance.
In this series I will assemble all the separate tips that I have learned or found into a step-by-step guide on the basic process (posted weekly). I do not consider myself an expert in PhotoScan. If you are familiar with the program and have any corrections or additions, please let me know.Each week, the previous step will be edited to include any comments and placed under the “Resources” menu to serve as a guide for beginners.
The previous steps can be found here.
Step 7: Building the Texture
Time for the final step in this series, texturing your model! If you only plan to use your model for 3D printing, then this part is unnecessary. However, one of the strengths of photogrammetry is that the photos themselves can be used to make your model look like the original object.
Changing the High Contrast Images
First of all, if you used edited, high contrast images in Step 2 we will want to change them back so the final texture is accurate (otherwise skip this part and move on to “Texturing” section). To do this:
- Right click one of your images in PhotoScan and select “Change Path…” on the menu that appears.
- A window will pop up, navigate to your original, unedited photos.
- Only the image that you right clicked on will show up, that is fine. Select it and click “Open.”
- A window titled “Relocate Photos” will appear. Select “Entire workspace” and hit “OK.”
You now have a model built with the high contrast images and the unedited images in place for your texture.
To add a texture to your model, go to your “Workflow” menu one last time and select “Build Texture…” A window will pop up with some more options.
- “Mapping mode” should be on “Generic” most of the time. “Adaptive Orthophoto” might be good if you are working with aerials or a relatively flat subject.
- “Blending mode” should be on “Mosaic (default)” as this will chose the most appropriate photo for the texture.
- “Texture size/count” will depend on the detail you want and your system requirements. The first box indicates the dimensions of the texture image. Larger numbers will give you finer detail (so long as your photos are in a high enough resolution) but can be very taxing on your computer’s RAM if they are too big. The second box will help you get around that by producing multiple files instead of just one large one.
Under the “Advanced” tab you will find:
- An “Enable color correction” checkbox which is supposed to even out lighting from photo to photo. I leave this unchecked.
- An “Enable hole filling” checkbox which will attempt to add a texture to places that were not covered by the photos. Depending on the object, how big the hole is, and how concerned you are with accuracy, the program’s attempt to fill these spaces in is usually obvious, but better than nothing.
Click “Okay” when you are satisfied. When PhotoScan is done processing you have a finished 3D model! You can now upload it directly to Sketchfab under the “File” menu or export it (obj or stl is recommended) to print or work with it in Blender or Meshlab.
That concludes the Basic PhotoScan Process series but there is plenty more to talk about. This final entry will be added to the permanent page next week. If you have a tutorial series you would like to see or do, just let us know!