planefit.py

# ##### BEGIN GPL LICENSE BLOCK #####
#
#  PlaneFit, (c) 2017,2018,2020,2024 Michel Anders (varkenvarken)
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; either version 2
#  of the License, or (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to the Free Software Foundation,
#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
#
# ##### END GPL LICENSE BLOCK #####

bl_info = {
    "name": "PlaneFit",
    "author": "Michel Anders (varkenvarken)",
    "version": (0, 0, 20240119092744),
    "blender": (4, 0, 0),
    "location": "Edit mode 3d-view, Add-->PlaneFit",
    "description": "Add a plane that best fits a collection of selected vertices",
    "warning": "",
    "wiki_url": "",
    "category": "Mesh",
}

import numpy as np


def planeFit(points):
    ctr = points.mean(axis=0)
    x = points - ctr
    M = np.cov(x.T)
    eigenvalues, eigenvectors = np.linalg.eig(M)
    normal = eigenvectors[:, eigenvalues.argmin()]
    return ctr, normal


def orthopoints(normal):
    m = np.argmax(normal)
    x = np.ones(3, dtype=np.float32)
    x[m] = 0
    x /= np.linalg.norm(x)
    x = np.cross(normal, x)
    y = np.cross(normal, x)
    return x, y


import bpy


class PlaneFit(bpy.types.Operator):
    bl_idname = "mesh.planefit"
    bl_label = "PlaneFit"
    bl_options = {"REGISTER", "UNDO"}

    size: bpy.props.FloatProperty(
        name="Size", description="Size of the plane", default=1, min=0, soft_max=10
    )
    separate: bpy.props.BoolProperty(
        name="Separate",
        description="Generate the plane as a separate object",
        default=False,
    )

    @classmethod
    def poll(self, context):
        return context.mode == "EDIT_MESH" and context.active_object.type == "MESH"

    def execute(self, context):
        bpy.ops.object.editmode_toggle()
        ob = context.active_object
        me = ob.data
        count = len(me.vertices)
        if count > 0:  # degenerate mesh, but better safe than sorry
            shape = (count, 3)
            verts = np.empty(count * 3, dtype=np.float32)
            selected = np.empty(count, dtype=np.bool)
            me.vertices.foreach_get("co", verts)
            me.vertices.foreach_get("select", selected)
            verts.shape = shape
            if np.count_nonzero(selected) >= 3:
                ctr, normal = planeFit(verts[selected])
                dx, dy = orthopoints(normal)
                if self.separate:
                    bpy.ops.mesh.primitive_plane_add(location=ob.location)
                    me = context.active_object.data
                    for vi, co in zip(
                        me.polygons[0].vertices,
                        [
                            ctr + dx * self.size,
                            ctr + dy * self.size,
                            ctr - dx * self.size,
                            ctr - dy * self.size,
                        ],
                    ):
                        me.vertices[vi].co = co
                    context.view_layer.objects.active = ob
                else:
                    # can't use mesh.from_pydata here because that won't let us ADD to a mesh
                    me.vertices.add(4)
                    me.vertices[count].co = ctr + dx * self.size
                    me.vertices[count + 1].co = ctr + dy * self.size
                    me.vertices[count + 2].co = ctr - dx * self.size
                    me.vertices[count + 3].co = ctr - dy * self.size
                    lcount = len(me.loops)
                    me.loops.add(4)
                    pcount = len(me.polygons)
                    me.polygons.add(1)
                    # me.polygons[pcount].loop_total = 4
                    me.polygons[pcount].loop_start = lcount
                    me.polygons[pcount].vertices = [
                        count,
                        count + 1,
                        count + 2,
                        count + 3,
                    ]
                    me.update(calc_edges=True)
            else:
                self.report(
                    {"WARNING"},
                    "Need at least 3 selected vertices to fit a plane through",
                )
        bpy.ops.object.editmode_toggle()
        return {"FINISHED"}


def menu_func(self, context):
    self.layout.operator(
        PlaneFit.bl_idname, text="Fit plane to selected", icon="PLUGIN"
    )
    self.layout.operator(
        PlaneFit.bl_idname, text="Fit separate plane to selected", icon="PLUGIN"
    ).separate = True


def register():
    bpy.utils.register_class(PlaneFit)
    bpy.types.VIEW3D_MT_mesh_add.append(menu_func)


def unregister():
    bpy.types.VIEW3D_MT_mesh_add.remove(menu_func)
    bpy.utils.unregister_class(PlaneFit)


if __name__ == "__main__":
    register()