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This protocol describes the process of phenotyping branching coral using the 3D model editing software, MeshLab. MeshLab is a free, straightforward software to analyze 3D models of corals that is especially useful in its ability to import color from Agisoft Metashape models. This protocol outlines the steps used by the Kenkel lab to noninvasively phenotype Acropora cervicornis colonies for total linear extension (TLE), surface area, volume, and volume of interstitial space. We incorporate Agisoft Metashape markers with our Tomahawk scaling system (see Image Capture Protocol) in our workflow which is useful for scaling and to improve model building. Other scaling objects can be used, however these markers provide a consistent scale that do not obstruct the coral during image capture. MeshLab measurements of TLE have been groundtruthed to field measures of TLE. 3D surface area and volume have not yet been compared to traditional methods of wax dipping, for surface area, and water displacement, for volume. However, in tests with shapes of known dimensions, i.e. cubes, MeshLab produced accurate measures of 3D surface area and volume when compared to calculated surface area and volume. For directions to photograph coral for 3D photogrammetry see our Image Capture Protocol. For a walkthrough and scripts to run Agisoft Metashape on the command line, see https://github.com/wyattmillion/Coral3DPhotogram. These protocols, while created for branching coral, can be applied to 3D models of any coral morphology or any object really. Our goal is to make easy-to-use protocols using accessible softwares in the hopes of creating a standardized method for 3D photogrammetry in coral biology. Go to http://www.meshlab.net/#download to download the appropriate software for your operating system. P. Cignoni, M. Callieri, M. Corsini, M. Dellepiane, F. Ganovelli, G. Ranzuglia MeshLab: an Open-Source Mesh Processing Tool Sixth Eurographics Italian Chapter Conference, page 129-136, 2008 DOI dx.doi.org/10.17504/protocols.io.bgbpjsmn
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