Find a Object Oriented Bouding Box (OOBB) in Blender

find_oobb.bpy.py

# This example assumes we have a mesh object selected

import bpy
import bmesh
import numpy as np

def getCentroid(A):
    return np.mean(A,axis=0)

def getSE3FromPointcloud(A):
    A = np.array(A)
    print (A.shape)
    cen = getCentroid(A)
    cov = A - cen
    print ("centroid %s" % (cen))
    u,s,vh = np.linalg.svd(cov, full_matrices=True)
    np.set_printoptions(suppress=True)

    return ((vh[0,0],vh[0,1],vh[0,2],cen[0]),
            (vh[1,0],vh[1,1],vh[1,2],cen[1]),
            (vh[2,0],vh[2,1],vh[2,2],cen[2]),
            (0,0,0,1))

def findAABB(found_SE3, A):
    D = []
    found_SE3 = np.array(found_SE3)
    found_SE3_i = np.linalg.inv(found_SE3)
    for p in A:
        D.append(found_SE3_i@[p[0],p[1],p[2],1])
    print(np.around(D,decimals=3))
    co_min = np.min(D, axis=0)[0:3]
    co_max = np.max(D, axis=0)[0:3]
    diff = (co_max - co_min)*0.5
    return np.flip(np.sort(diff)) 
        
    A = np.array(A)
    print (A.shape)
    cen = getCentroid(A)
    cov = A - cen

    print ("centroid %s" % (cen))
    u,s,vh = np.linalg.svd(cov, full_matrices=True)
    np.set_printoptions(suppress=True)

    return ((u[0,0],u[0,1],u[0,2],cen[0]),
            (u[1,0],u[1,1],u[1,2],cen[1]),
            (u[2,0],u[2,1],u[2,2],cen[2]),
            (0,0,0,1))


if __name__=="__main__":
    # get active object
    obj = bpy.context.active_object

    # get its vertices in world coordinate system
    A = []
    for v in obj.data.vertices: 
        co_final = obj.matrix_world @ v.co
        A.append([co_final.x,co_final.y,co_final.z])
    
    
    nn = obj.name+"_svd "
    if nn in bpy.data.objects:
        empty = bpy.data.objects[nn]
    else:
        empty = bpy.data.objects.new( nn, None )
        empty.empty_display_size = 1
        empty.empty_display_type = 'CUBE'
        bpy.context.collection.objects.link(empty)
    found_SE3 = getSE3FromPointcloud(A)
    # apply rotation (it should apply translation as well, but it is not    
    empty.matrix_world = found_SE3
    # apply translation
    empty.location = getCentroid(A)
    scale = findAABB(empty.matrix_world , A)
    print ("AABB :",np.around(scale,decimals=3))
    empty.scale.x = scale[0]
    empty.scale.y = scale[1]
    empty.scale.z = scale[2]
                                                 
    print ("Done")