HOW TO INSTALL

Start by downloading the .py file. In Blender, go to Edit > Preferences > Add-ons. Click Install in the top bar, search for the .py file and click Install add-on from file. Then, type "ICP" in the search bar. Enable the addon and click Save preferences. You are now able to use the addon!

READ ME

The ICP Registration addon is visible in Object Mode in the Sidebar (hotkey N) > ICP Registration.

INITIAL ALIGNMENT

If the two objects differ substantially in location or rotation, a pre-alignment should be performed. Select two mesh objects. Press "Place Landmarks" and place 4 or more landmarks on corresponding positions on both objects. Make sure the number of landmarks is equal. Press ESCAPE to cancel or ENTER/RETURN to confirm. Landmarks of selected objects can be deleted by pressing the "Delete Landmarks" button. After placing landmarks on both objects, perform initial alignment by pressing "Perform Initial Alignment". The active object will stay in fixed position.

* Allow Scaling
When checked, the moving object is allowed to scale uniformly. Otherwise, only location and rotation are taken into account.

ICP ALIGNMENT

Select two mesh objects. Make sure the settings are as desired and press "Perform ICP" to start the alignment process. The active object will stay in fixed position. Press ESCAPE to cancel or ENTER/RETURN to confirm.

* Allow Scaling
When checked, the moving object is allowed to scale uniformly. Otherwise, only location and rotation are taken into account.

* Use Vertex Selections
When checked, only the selected vertices (in Edit Mode) are used for registration. As such, the registration can be focused on a specific region of interest.

* Iterations
The number of iterations used for registration. Increase to improve accuracy, decrease to decrease processing time.

* Outlier Percentage
Fraction of outliers (non-corresponding points between the two objects). For example: when set to 25%, 75% of the best matching point pairs between the two objects is used for registration. Increase to improve registration accuracy in noisy objects, decrease if the meshes correspond to a large extent.

* Downsampling Percentage
Fraction of downsampling for both objects. For example: when set to 25%, 75% of the total (or selected) vertex count is used for registration by means of a random sample. Increase to improve speed in objects with large meshes, decrease to improve accuracy.

TRANSFORMATIONS

* Export Transformation
Export the transformation matrix (location, rotation and scale) to a .txt file. The drop-down menu gives the choice to export the combined initial and ICP transformation, or only either one of these.

* Set Transformations
Set transformation of an object from .txt file. Select the object that should be transformed, press "Set Transformations" and browse for the desired .txt file.