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  • I have an animation that loops and has two phases: "cube_object" goes to point x, spins - repeat).
  • Now everytime the "spin" animation is finished (or the "cube_object" reaches a certain location...?), I'd like to spawn an object on a random position with Python.
  • If there are 10 objects spawned stop the animation and change camera angle to another scene.

Imagine a worker in a game that chops wood and every time he finishes chopping a new log spawns. After 10 logs - something new happens.

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Try this example that will spawn a random cube everytime the frame == 10, it will stop after 5 cubes:

import bpy

# this is for the random position, imports the random() function from random library
from random import random

# this holds how many cubes were created and what the cap is
spawned_cubes = 0
max_cubes = 5

def spawn_object(scene):
    """This function will be run everytime before frame changes because it is added in the callback list"""

    global spawned_cubes
    global max_cubes

    # read the current frame number
    # if it is 10 and number of spawned cubes is less than max_cubes place a cube
    # if the frame number is not 10 just end and do nothing
    if scene.frame_current == 10 and spawned_cubes < max_cubes:
        loc = (5-10*random(), 5-10*random(), 5-10*random())
        bpy.ops.mesh.primitive_cube_add(enter_editmode=False, location=loc)
        spawned_cubes += 1
    return

# add spawn_object function if there isnt one in bpy.app.handlers.frame_change_pre callback list
# the function needs to be added there only once
# everything thats in that list will be executed before any frame change
if spawn_object not in bpy.app.handlers.frame_change_pre:
    bpy.app.handlers.frame_change_pre.append(spawn_object)

This uses the app handlers callback list. In your spawn_object function you can test any property - for example the location of your cube_object, or some frame value etc.

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  • $\begingroup$ thank you, this was very useful! If you have time, could you explain what "from random import random" at the beginning does? And if I get the solution right, your code counts the frames and every X frame calls the function, right? The code spawns 3 cubes now btw... :) And to be honest, I don't get this part at all: # add handler if not in app.handlers if spawn_object not in bpy.app.handlers.frame_change_pre: bpy.app.handlers.frame_change_pre.append(spawn_object) However the script works without it. And how would you stop that loop? After x frames or after x spawns? Thanks! $\endgroup$
    – Sputi
    Commented Dec 16, 2014 at 15:43
  • $\begingroup$ no, the function is not called every X frames, it is called every frame, but only on frame 10 it will do something. You can add counter how many cubes it created for stopping the generation - Ill add that into the example $\endgroup$
    – Jaroslav Jerryno Novotny
    Commented Dec 16, 2014 at 15:57
  • $\begingroup$ The from random import random tells python to import the random() function from the random library. More info can be found here. docs.python.org/2/library/random.html#random.random $\endgroup$
    – Vader
    Commented Dec 16, 2014 at 15:58

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