Step 3 : Photogrammetry
- Elliott Round
- Nathan Dunne
- Duncan Baird
When is a job ready?
When a job’s status is DO SOLVE, the Images button will open the photogrammetry images when clicked. The images in this directory must be used for photogrammetry for Marso to work correctly, however they can be adjusted as long as the name, shape, and orientation of each image is unaffected.
Run your Photogrammetry
You can now proceed with your normal photogrammetry reconstruction workflow. You must use the exror jpg files created in the previous step.
We currently support Agisoft Metashape or Reality Capture as your photogrammetry application.
Checklist
3D Mesh and camera solve
It is important to get a good solve of the cameras within the scene, poorly solved cameras can lead to artifacts in the material measurement later on. We recommend attempting to re-align any bad camera solves or removing those cameras from the 3D solve all together.
A high number of polygons in the mesh may cause Marso to exceed the available VRAM on your system. If this occurs, simplify the mesh and reattempt the process. Marso does produce highly detailed normals even on medium to low poly meshes. See Examples
When drawing a bounding box around your subject for mesh reconstruction, it is important to also include any stands or supports (if not using the mask mesh feature). This additional geometry will ensure that pixels are correctly traced onto this geometry and not onto the subject itself. Using one of the lower cameras (as shown below) can be a helpful reference to see how much geometry is required to avoid unwanted pixels being projected onto the subject.
UV Unwrapped Mesh
The 3D mesh that Marso will create textures for will require a UV unwrap. By default, a 3D mesh within a photogrammetry application will not have a UV, so you must first run the texturing process within the application or UV unwrap manually. (The mesh must have a single unwrap not multiple)
Scale the Scene
It is essential that the 3D scene is correctly scaled, we suggest using markers to automatically set the scale of a scene within RealityCapture or Agisoft Metashape Pro.
Agisoft Metashape Standard does not offer a way to automatically set scale. For best practice, we recommend using Blender (a free 3D application) to do this by hand.
Open a new ‘General’ blender scene and Delete all of the Default objects, you scene should look like this:
To Import an Alembic file : File -> Import -> Alembic
After importing, the mesh and cameras should be in your scene. Create an empty object, this will be used to apply the same scale to the mesh and all the cameras:
Select everything except the ‘Empty’:
Then Shift+Drag the selected items into the empty:
It should look like this:
Using the measure too 
Then compare this distance to the real life distance. If you divide this distance by the real life distance you end up with a scale factor.
On the object properties menu for the ‘Empty’, insert the computed scale factor into the three scale input boxes:
Use the measure tool again to confirm the distance is now correct.
Now select all cameras and the mesh, press Alt+P to bring up the Clear Parent dialog, and select Clear and Keep Transformation:
Delete the ‘Empty’ from the scene, your outline should only have the cameras and mesh now:
Now export the scaled alembic:
This scaled alembic is the one you want to select during the run dialog in Marso.
Export Alembic Mesh & ST Maps
Export an Alembicabcfile with cameras & normals enabled, also export an ST Map as anexrwhich will be used to account for lens distortion. It is important to use an ST map created within the photogrammetry application rather than