Researching workflows for photogrammetry and reflectance transformation imaging is just part of the work we are doing on this project. The other part of our work is to test different equipment and software. One of the big decisions we have to make is in our 3D mesh editor. Once the photos have been captured for photogrammetry and after the photos have been taken into Agisoft’s Photoscan for processing, you should now have a 3D mesh. This 3D mesh is Photoscan’s best guess at what the actual object looks like. It is far from perfect and requires editing. Holes in the mesh might need to be filled or superfluous surfaces deleted. A building as large as Abiquiu has to be photographed over the course of several days. Each day is processed in Photoscan as a separate mesh. This creates many different individual 3D meshes that need to be cleaned up and joined together to create a single composite mesh. Initially we chose Meshlab as our mesh editor. It is free and open source, which is very important for two reasons:
1) Full disclosure of all data transformations. Any changes to the original pictures across all of the pixels in each picture is visible to us. It is open and free from secrets created by proprietary software. This makes the data transparent and ideal for scientific recording.
2) With open source we have the ability to apply our own scripts and transform it in ways that are specific to our needs. This frees us from the constraints place on us by proprietary software.
We discovered that there were features that were lacking in Meshlab that made editing and joining difficult and time consuming.
1) There is no undo button. Professional 3D mesh editors all share a non-destructive editing environment. Any changes made to Meshlab are final. If a mistake is made, it is necessary to reload from you last save point.
2) It is not well documented. There is an instruction manual, but there is not a very big community of users, or a large number of tutorials available. This makes learning the software difficult.
After researching various alternatives we decided that Blender was our best bet for mesh editing and joining. Blender is free, open source, cross-platform compatible, extremely robust, contains a wealth of documentation, and boasts a very helpful learning community. Since Blender contains so many features, there is a steep learning curve in getting proficient at mesh manipulation, but the time spent in learning the software is well worth it. Thanks to the Blender, we will soon be putting up some very high quality 3D meshes of the Abiquiu House on the blog!
So to be clear for those of you who are Meshlab enthusiast and are screaming at your computer “These guys are just noobs! Meshlab is awesome if you know how to use it!” Yes you are right, but that is exactly our point. We ARE noobs as are all of the people who will be using this software in their work. Blender does have a steep learning curve but there is plenty of help. We have yet to have a question about the software that wasn’t answered in print as well as with accompanying video tutorials.
So while we will keep a link to Meshlab on our equipment and software page, Blender is our recommendation for anyone editing meshes exported from Photoscan.