[PYTHON] Create a shape on the trajectory of an object

To fill in the blanks in Blender Advent Calendar 2020 Publish the script used at work

A script that creates an object with an animated trajectory of the object

Record the movement of the rendering range of the active object It is such a specification that a mesh is stretched with the selected object as a cross section.

make_trailobject.py

import bpy
import os
import math
from mathutils import Vector, Euler, Matrix, Quaternion

#Creating a mesh object from data
def add_mesh_from_data(name,vertices,faces):
    mesh = bpy.data.meshes.new(name)
    obj = bpy.data.objects.new(name, mesh)
    bpy.context.scene.collection.objects.link(obj)
    mesh.from_pydata(vertices, [], faces)
    mesh.update()
    return obj 

#Get the movement of objects in the range of the rendered frame in a matrix
def get_matrix_all_flame(obj):
    #Get frame range
    frame_start = scene.frame_start
    frame_end = scene.frame_end
    matrix_list = []
    for t in range(frame_start,frame_end):
        #Current frame settings
        bpy.context.scene.frame_set( t )
        #Conversion matrix to global coordinates
        # Matrix()If you don't do it, matrix_Enter the list with a reference to world
        matrix_world = Matrix(active_obj.matrix_world)
        matrix_list.append(matrix_world)
    return (matrix_list)

#Sweep objects from orbital data
def create_trail(matrix_list, target, name):
    vertices = target.data.vertices
    point_num = len(vertices)
    line_num = len(matrix_list)-1
    
    edges =  [list(e.vertices) for e in target.data.edges]
    edges_num = len(edges)
    new_verts = []
    new_faces = []
    UV_list = []
    #Calculation of data to create a mesh
    for i, matrix in enumerate(matrix_list):
        #Add vertices
        for j in range(point_num):
            p2 =  matrix @ vertices[j].co
            new_verts.append(p2)
         #Add face
        for k,l in enumerate(edges):
            if i != 0:
                #Create face ID
                p1 = l[0] +(i-1)*point_num
                p2 = l[1] +(i-1)*point_num
                p3 = l[0] +i*point_num
                p4 = l[1] +i*point_num
                new_faces.append([p1,p2,p4,p3])
                #UV creation
                u1 = k/edges_num
                u2 = (k +1)/edges_num
                ##UV starts at the bottom left, so correct it to start at the top left
                v1 = 1 -(i-1)/line_num
                v2 = 1 -i/line_num
                #Coordinate setting
                UV_list.append(Vector([u1, v1])) 
                UV_list.append(Vector([u2, v1]))
                UV_list.append(Vector([u2, v2]))
                UV_list.append(Vector([u1, v2]))
                
    #Creating an object from data
    obj = add_mesh_from_data(name,new_verts,new_faces)
    #UV settings
    uv = obj.data.uv_layers.new(name="grid_uv")
    for i,p in enumerate(uv.data):
        p.uv = UV_list[i]

scene = bpy.context.scene
#Get the selected object
selected_objects = bpy.context.selected_objects
active_obj = bpy.context.active_object
#Get the trajectory of an object
mat_list = get_matrix_all_flame(active_obj)
#Sweep objects other than the active object
for target in selected_objects:
    if target == active_obj: continue
    create_trail(mat_list, target, "trail")

After selecting the plane to be the cross section, select the object you want to use the movement and execute.

In the script, UVs are arranged in a grid in the order of vertex IDs. Since the vertex IDs are often not in the order of the mesh The UVs created may not always be manageable This needs improvement.