Scripting rendering in max. Weird question

I have been trying to create an effect for some time now. It's hard to explain so forgive me if I ramble a little. It's a bit like the famous matrix shots, where the camera pans around an object (character) at a single time. However, additionally I want to show what the object looked like at previous times from that angle. In my case I want a moving bird to leave behind it a trail of what it looked like at previous times and do this while having a moving camera. It is like what I am trying to do in the linked video, but in full 3d with a moving camera.



I have tried various means of doing it in post processing but that severely limits camera movement. In order to achieve this effect I would like script/program rendering to do the following...

* At any given frame of the animation, max renders all previous frames but from the camera angle of the current frame of animation.
* It then saves this output in a specifically named folder (name corresponding to frame number from which the camera position is being taken.
* Ideally I would have these save as different layers of PSD files (with alpha maps) but I don't think this can be done. In that case I'll just set up a batch process to combine all the images into one new frame.

For example, at frame 3 one could see the object at frame three, but also the the object at frames 1 & 2 but from the camera angle at frame 3.

So what I would do for my animation is render the scene normally with all objects, ie the environment and other stationary objects as well as the animated birds. I would then like to go back and render out just the birds in the manner which I have described above. Then I would like to composite the two renders to create an final image where one can see moving objects as they do and have previously existed.

I'm wondering if what I have described is at all possible in max and it's probably not something that is encountered often. I personally have no idea how to implement this and would greatly appreciate any help on the subject.

Thank you,
Kieran

Hey Kieran,

That's a good question...but it is most definitely possible. Do you have any prior scripting knowledge?

What you would want to do is this:

-setup a script that enables you to render a sequence of frames that you can define

-have the script cycle through the timeline

-at each tick on the timeline, the script kicks off a new render, of all of the frames up to the current point on the timeline

-when it renders, it uses the "at time" function to get the positional data of the bird at all of the previous frames, without changing the camera angle

-once the script renders a single frame for each of the past positions of the bird, it moves onto the next frame.

Let me know if you need help writing it.

Thanks a million, seems to be working great. I haven't had a chance to get the images together into frames of animation but they look right. This could very well kill my hard drive BTW.

Thanks again,
Kieran

Lol, I do have a question.

What is the best way to combine these. I thought I knew how to do a batch process on them but it doesn't want to work. Any suggestions?

Hahah no idea mate

One possible suggestion: If you've got after effects, goto File--->Import. Select all of the files in one sequence, but don't check the "sequence" checkbox.

Hopefully all of the files will then import separately. Once that's done, select them all and drag them into a composition. They should all be layered now and you should just have to export the single frame

Hmm well you could write a render script (I guess) that creates a snapshot of your geometry at every previous frame....thus duplicating the geometry at each next frame so that at the end of something like a 100 frame sequence, you'd have 100 snapshots of the mesh at different points of time in your scene.

This could go screwy though because all of those objects would share the same lighting/shadows etc....so, for example, past meshes would be shadowed by future meshes etc.

Hmmm

The only other thing would be to write a script that simply saves the previous frames in memory and composites them in real time (sort of like how multi-pass motion blur or DOF works)....I have no idea how to do that though

Btw man I only just realized you're from Madison! I drove through that city on my way to Minneapolis once

Lol, Madison is a cool town, though you're much further from here now I guess. I might head up to Minneapolis this summer, apparently theres a bar named after me there.

I don't think I'd worry too much about shadows and stuff like that, not with my current project anyway. I planned on just rendering out things that this effect would apply to apply to, in my case crows, as a separate pass that I would composite on top of my previous animation.

Wouldn't placing those frames in the buffer still require the huge amount of renders I mentioned above?

Anyways, thanks for your input.

-Kieran

Well what I meant about the shadows is that will the increment of each frame, the previous frames would "pop" a little because new shadows would continually be introduced on the old instances.

As for the buffer thing, no...it would just export a 1:1 frame ratio. So a 300 frame sequence would only have 300 rendered frames. However, within MAX itself, yes...you'd still be rendering a TON of frames into the buffer

Haha...really no matter what you do there is going to be some time tradeoff...