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In Getting Started with Reactor in 3ds Max, Steve Nelle shows how to create realistic dynamic simulations that have objects recognize, collide and react to coming into contact with each other in 3ds Max animation projects. This course includes a detailed explanation of both rigid and soft body dynamics, reactor's various collection types, using constraints and soft body modifiers, and how to adjust and control a dynamic simulation's accuracy. Four start-to-finish projects are also included in the course, which show practical techniques for breaking objects apart, creating cloth simulations, adding rippling water effects to a scene, and more. Exercise files accompany the course.
Once your simulation has gone through its final adjustments and you are ready to commit to the work that's been done, you can bake in the animation that Reactor has assisted in making by creating the all-important keyframes that are necessary in order to go out to final render. This video will show you how that's done. Carrying over the scene that we were using to create our previews in the last video, I've renamed the file Creating Animation. Ready to go, we can now activate Reactor's keyframing command in one of a couple different ways. One of those options would be to go to the Animation pulldown menu at the top of the interface, heading then down to the bottom, choosing Reactor, then off to the right, choosing Create Animation.
We could've also instead decided to use the handy Quad menu, holding down the Shift+Alt keys and right- clicking with our mouse. When the dialog opens, we would then head down to the lower right-hand quadrant. The Reactor toolbar that we've docked on the left-hand side of our screen also gives us the same command as the very last icon at the bottom. But this time around I am going to choose to use the options in the Utilities section of the Command panel. The reason being is that from there I have the ability of choosing not just the number of frames in which I want my keyframes to cover, but I also have a couple of final accuracy settings that I can adjust all depending on my needs.
Let's head over to the right. We'll click on Utilities, then down into the Reactor commands. Let's say, for example, that I only want the keys that I generate to include the first 90 frames of my animation. To do that, in the Preview & Animation section, I can change my EndFrame to 90. Now, the other important settings in this section are covered in the video on controlling simulation accuracy, so I am going to go ahead and skip them here. With that new EndFrame number typed in, I think we are ready to go. Now, very important: creating keys is a pretty permanent thing. So before we go any further, I'd suggest that you always either save or hold your file at this point just in case you decide that those keys turned out not to be what you want after all.
It's a lot easier to simply reopen or fetch a file than it is to have to go down to the timeline and start uprooting keys. So next step, we'll go to the Edit pulldown menu at the top-left corner, choosing Hold. Okay, to create the keys, we'll go back to the right-hand side. Just a couple inches down below EndFrame, you'll see a button that says Create Animation. If you're ready to go, you can then click on that command. The Option box that opens, basically asking us one last time if indeed we want keyframes to be created, in there you can simply click OK.
Now after a moment of creating those keys-- and that delay will all be determined by the number of keys that Max has to create-- the process will be completed and we can then close that one open box. Okay, let's now scrub our timeline and see how things look. So that's pretty nice. Let's go ahead and play things back. Now, I want to show you something.
Go ahead and select one of the bricks in the scene and take a look at your timeline. The way a dynamic simulation works is by creating a key at every frame for each and every object that moves during the sim. So one of the drawbacks of a sim-type animation is that it can make for a pretty large file, all depending on the number of frames that are simulated and how many objects there are in those frames. One of the things that you can do to minimize some of that bloat is to use a helpful option in Reactor that analyzes the keys that have been created and carefully eliminates any redundant-- in other words, unnecessary--keys, while still maintaining the integrity and accuracy of your keyframe movement.
It's pretty neat how it works. To get to it, we'll go back to Utilities section on the right. In that column under the Utilities tab, you'll find a control called Key Management. The Reduction Threshold setting in that category determines just how aggressively Reactor will go about searching for unneeded keys. Keeping that Reduction number set at 0.5 usually does a pretty good job, so we'll leave it there. Right below that, we can now click on Reduce Now. Take a look at that. The Key Management utility has reduced the number of keys in our scene by over 17,000.
That's quite a healthy reduction. Let's go ahead and close the box, and we'll play things back. So, check that out. The behavior of simulated objects is almost exactly the same way it was before the reduction. But if you look at the number of keys down on the Timeline, you'll see that we've been able to reduce things by, in this case, almost 30%. Now if your animation doesn't end up looking maybe quite as accurate as it did before the reduction, you can always retrace your steps and maybe lower your Reduction Threshold not quite so much.
So there you go with creating keys for your simulation once the preview work is done. Just be sure to always remember to save or hold your work before getting down to setting those keys.
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