Fologram uses collections of QR codes called markers to precisely locate your model in physical space.
When your HoloLens or mobile device detects a marker in physical space, Fologram will snap the coordinate of the marker in your digital model to the corner of the detected QR code. If Fologram has previously detected other markers in your space, the nearest 3 markers will be used to position your model and correct for drift. Markers must be precisely located in space to precisely position models.
If you cannot accurately position a marker at its specified coordinates in space, then Fologram will not be able to reliably correct for drift. Imprecision in marker placement can lead to very dramatic movement in hologram position that is often worse than ordinary drift. We recommend positioning markers along a line using a tape measure, in a grid using a cross laser, or on existing survey marks to ensure that they are accurately located. For more information on placing markers, see this guide.
Creating markers
Use the
XRMarker command to add a marker to your model. The command will first prompt you to define where the marker will be located relative to your model, and then to provide an ID (name) for the marker. It’s best to give the marker an ID that can be used to easily differentiate between markers, e.g. “BenchRight” or “NESlabCorner”. 
Markers appear in the Rhino viewport as text dots. You can change the position of a created marker by moving the text dot in Rhino, and can edit the ID by double-clicking on the text dot or making changes in the properties panel.
Printing markers
Use the
XRMarker command and then click the PrintAll parameter launch app.fologram.com in your browser with a pre-filled list of marker IDs to print. 
Click Print to generate a PDF of your markers. Print the PDF on an appropriate page size for your use case. You should print your markers on the smallest possible page size such that they are still easy to detect during your task. We recommend A4 or A3 for most use cases. You can re-use existing printed markers for multiple models. Simply specify the ID of the existing marker you wish to use when creating a new marker in Rhino. For more tips on printing and reusing markers see this guide.
Alignment modes
Fologram can align physical and digital marker positions using one of two modes set in the
XRProperties command. When Alignment is set to Z-up, Fologram will attempt to reposition your digital model and perform rotation around the Z axis to best match detected marker positions. This is useful for situations where you want to use a digital model as a guide for determining plumb and level and do not want the model to freely rotate in all axes. When Alignment is set to Free, Fologram will attempt to rotate your model in all axes to best fit detected and digital marker positions. This is useful in scenarios where markers are used to overlay digital models on moving objects that will be rotated and repositioned in space arbitrarily. For more information, see this guide. Single marker placement
When using only a single marker, Fologram will match the X and Y axes of the QR code to the X and Y axis of the Rhino model. Rotating the printed marker will rotate the digital model in mixed reality.
Placing models with a single marker is not accurate or reliable and is only recommended for visualization use cases
Multiple marker placement
When locating models with multiple markers, Fologram uses only the corner point of the detected QR code indicated by the purple arrow and fold line. The nearest 3 markers are used to position your model.
Troubleshooting and limitations
For help with detecting QR codes, check this guide.
For common issues with placing markers, check this guide.
For placement strategies, check this guide.
Precision is impacted by a number of environmental and behavioural factors as well as by the proximity of a user to markers and the precision with which markers can be located in space. To determine expected precision in your workspace, follow the Evaluating Precision guide.