Reverse Explosion?


I’m using blender to make models of chemical reactions, and I have to show a molecule come together spontaneously. Now, I can make one blow up, and coming together should just be the reverse of that, but does anyone know how to reverse it? I have to use the molecule after it comes together, so I can’t just blow it up then reverse the video, unfortunately.

Much obliged,

You could of course reverse the vid and do a second that starts just as the other ends. Blend them together in the VSE (Video sequence Editor in Blender).
Another possibility would be to animate the time value of your vid. Try to use negative time values for your reversal :wink: I haven’t done it myself but I’m pretty sure that it should work. If you’re uncertain wait for so else to elaborate further or better do a forum search for that approach.

EDIT: a negative time value in the IPO window doesn’t help. It seems to work this way: on the y-axis you have the frame number that is beeing displayed as your animation progresses. the x-axis shows the actural frame number of your final animation
So in your case your graph needs to have a high y-value (equal the number of frames your explosion animation has) and then go down to 1 (the frame your explosion starts).
Have a look at the example I made (the cube normally would move from center to top-right position but is inversed by the time ipo; delete the time ipo to see that original animation)

Hope I could help :wink:


animated_time.blend (127 KB)

Thanks a lot! The time data channel was just what I was looking for. I’ll let you know if I manage to reverse-engineer and explosion (this could start a trend).

Right, the time idea worked perfectly. I set all of the spheres up as rigid bodies, and made the radius large enough that they overlapped, then recorded IPOs from the game data to record the explosion and reversed for the duration of it to have the molecule come together. The only problem I’m now left with is that all the atoms in the molecule are now frozen at frame 0 for the rest of the animation, so I can’t carry on working with them, or even hide them on another layer and use a copy.

Also, anyone know how to apply logic settings to several objects at once? I have 80 spheres for atoms and I had to do them all individually. I can’t even find a link function for logic.

Much appreciated.

ok, simples things first:

to copy logic settings from one object to as much other objects you want, do this:
Select all objects you want the logic settings to be copied to. Then, hold shift and add the “master” object (that contains the logic bricks) to the selection. You can now copy the settings by pressing ctrl+c --> logic bricks :wink:

As for the rest, I need to think about it a bit

EDIT: ok, got it, it’s simple as well:

You just have to tweak your time ipo to go on with your animation.

What you did so far is this:
You animated the explosion let say from frame 1 to 100. Then you used the time ipo to tell blender to use frame 100 as your first real frame (by setting an ipo at y = 100 and x = 1). For ne next 99 real frames you reverse the initial animation by putting the next ipo point at y = 1 and x = 100.
So to go on with your animation, you will just have to set the next time ipo point to y = 101 and x = 101 and from there on extrapolate in a 45° graph to always have a 1:1 ratio of x:y.

As for the workflow: generally you animate your whole thing as you like and ignore the fact that the first explosion part is not the way you really want it. At this point you would have a normal time ipo of y=x. You alter that time ipo to just invert the frames you want and afterward you have to make sure that you set the time ipo back to y=x for the remaining frames.

Maybe my explanations are a bit confusing, tell me if there is still something unclear for you.

Looking forward to your final animation :wink:

good luck!

For that copying trick you’ve earned my eternal gratitude and a non-essential organ of your choice (I recommend a kidney).

I actually solved the explosion thing by making a new scene that’s identical, but without the explosion and time data blocks. I did the rest of the animation there and am now running them together. I think it’s my safest option, lest all this tomfoolery catch up with me later.

And I did actually think about that as a solution to the time ipo problem, but since it would have meant individually editing ALL of the 80+ molecules, I decided to find a way around it. However, with your handy copying hint, it’d be perfect.

Thanks again.