Importing 3D SfM models to Blender

The assignment for the paper is to build a reconstruction of an Egyptian coffin. We were given photographs of an existing coffin lid part. I have already build a 3D model with the photographs using Structure from Motion with Agisoft Software.
The first step to building a 3D reconstruction was importing this SfM model to Blender.
When opening Blender, I started with a General New File, this brings you to the default screen. There will be a cube, a camera and a light already visible. The cube will disturb the scene when importing an object, but because I learned that it’s important later, I now just hide it by clicking on the eye symbol next to it. I then went to File –> Import –> Wavefront (.obj) (Image 1). Or if you have a different file format, choose the one you want to import. I selected my file and thus the object showed on my screen.

Image 1: Importing

My 3D object wasn’t centered, so I right clicked –> Set Origin –> Geometry to Origin. To easily rotate the object, I seleced it, pressed the rotate button on the left toolbar (Image 2) or after a while used the shortcut R. With the shortcut R, when afterwards pressing X, Y or Z, it will rotate only on that chosen axis. This makes rotating easier and faster.

The last step was scaling. This is only possible if you either now the dimension or the SfM model has a visible scale you can use. For this to work, I needed to change the shading of the model. By clicking the third or second to last circle (radio button) on the top left workspace in Blender it changes the shading of the object. Now the texture of the 3D model can be seen. I now unhid the cube from the beginning and scaled the cube to the measurement I could see on the 3D object (10 cm). The easiest way to scale the cube is pressing N or clicking the small arrow on the righthand side to show the Sidebar (Image 3). There I wrote 0.1 m into the Dimensions field at the bottom. To move the cube I pressed G and once again X, Y or Z for the axis I wanted to move on. To scale the SfM model, I first pressed the scale button on the lefthand side and then learned the shortcut S. As with the rotate or move shortcut, it is again possible to follow pressing S with X, Y or Z to scale on that specific axis. It is also helpful to change the view for scaling: I change between pressing either on the blue, red, green coordinate system and clicking on either X, Y or Z or using the shortcuts: Numpad1 (x), Numpad3 (y), Numpadz (z).
After scaling the model, it is important in the long run to apply the new scale (only works in object mode). I went to Object –> Apply –> Scale (or press Ctrl-A or Cmd-A and Scale) (Image 4). And of course: Save!

Image 3: Set Dimensions
Image 4: Apply Scale

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