Dynamic, script-based animations of object creation and deletion

Question

New to blender. Here's my dilemma. I am dynamically animating a protein network using a python-script using user-provided text-files. The animation is done using key-framing for each object's actions (see below - self.frame_number and self.disjointed_frame allow the class in question to remember what frame the animation is on)

    def add_progressive_location_keyframe(self, frame_step):

        bpy.context.scene.frame_end += frame_step
        bpy.context.object.keyframe_insert(data_path="location", frame=self.frame_number)
        self.frame_number += frame_step
        self.disjointed_frame += frame_step

So far, animating reactions that merely involve the transloation of one protein from one location to another have worked fine. However, some reactions involve two proteins forming a complex, a new protein. In this case, I have to dynamically delete the two reactants in a certain key-frame and in that same frame create the product. However, I cannot add a key-frame to an object I have deleted and I am unable to add a key-frame to an object that doesn't yet exist. This results in the two reactants being deleted and the product being formed in frame 0 (the first one).

My question: How can I add key-frames to these objects in order to dynamically delete and create them in certain frames? Is there a work around I am unfamiliar with? Your help is much appreciated.

Answer 1

In that case I propose

• preprocess the file into separate files per frame ( Alternatively create a cache dict if you have plenty of RAM, that way you avoid having to deal with writing/reading extra files :) )
• store each cloud of atom types and their coordinates something like

this:

 C x y z
 C x y z
 C x y z
 N x y z
 N x y z 

• write a file reader that can take each frame's file and

  • on the first frame

    1. check if the object in the next step exists already, skip this step if it does.
    2. create a vertex based mesh object for each type of atom ( ie create a vertex for every atom of one type and put those in an object named something like atom_cloud_C, and do the same for all other atom types ). Meaning, if your file only has 3 C atoms, that your atom_cloud_C only has 3 verts.

    3. on subsequent frames you read the next frame's file and overwrite the coordinates of each atom, for all atom types.

       code:

       f_v = list(itertools.chain.from_iterable(verts))
       mesh.vertices.foreach_set('co', f_v)
       mesh.update()
       

• This produces clouds of atoms as different objects, which get updated every frame.

• Then create the spheres that represent each atom type (only need one sphere per atom type)
• Then use the dupli feature set to Verts to duplicate the various spheres that represent the atom. (this is a low memory way to display many spheres )
• instead of keyframing it all, you can attach a bpy.app.handlers.frame_change_pre to perform a function on each frame change (pre or post), examples for this can be found in the documentation.