Week 4: Photogrammetry

For this weeks assignment we were supposed to do 3D scanning but unfortunately it broke before I got to use it so I defaulted to photogrammetry. I used photoshop to process pictures, Agisoft Metashape to make the point cloud/mesh and Autodesk Meshmixer to touch up the model a bit in the end.

For photogrammetry, ideally you want a nice 360deg view around the object at variable heights. Some prefer to take pictures to get precise positioning but for me, I prefer to take a video which I then import into photoshop to turn into a image sequence to ensure that I had plentiful data to work with even if a decent amount of it ends up being non-useable (perhaps not recommended later on for those with lower-spec computers). I bumped the full video frame count from about 1900 down to about 400, skipping to every 5th frame in photoshop.

After importing all the images into Metashape, I set it to align the camera on high setting, this took a few minutes for me and at first glance it seems very messy but you can start to see the shape of the salt container when looking closely.

Next up is creating the dense cloud, which refines the data a bit further, now making it quite apparent that the model is coming out pretty decently. This is also where I tend to get rid of all the extra points I don't need, since its easier to tell what's what compared to the initial cloud. There is an argument to be had for getting rid of them beforehand to make sure that the dense cloud only uses points that are relevant therefore making the model more accurate too.

Again in Agisoft, I make the mesh based off the dense cloud in the step before. This gives a pretty good rough model, which I export as an .obj to be used in Meshmixer.

Meshmixer provides some simple transform/sculpting tools. You can even combine shapes if you wanted to. I was lucky that the original model came out without any holes whatsoever but there were some areas that definitely required some smoothing out. I used the drag tool to bring the divots out then the flatten tool to smooth everything down. Unfortunately the details are somewhat lost in the translation from photos to 3d model, but that is a rather unavoidable shortcoming of doing photogrammetry.