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If our animation looks good then we can go ahead and render it, but there are a couple of things we need to do first. First of all the simulation is not fully in motion on frame one of the time line, it's all ready kind of standing straight up on frame one. Before we can render a dynamic simulation there's a couple things that we want to do. First of all we don't have an initial state to the simulation, it's in a kind of neutral state on frame one. And what I'd like to have is the grass fully in motion on frame one.
And to do that, we'll need to set an initial state. And this is similar to what you would do in other dynamic areas of Maya such as Ncloth or Particles. However, the process is kind of a lot different and kind of more complicated. What we need to do is we need to consider the nHairs start curves and rest curves. You can't see it here but there's multiple curve systems under the hood. And right now we don't have any conditions for the start curves or the rest curves.
And we need to define both of those. If we only define the start curves then we would never be able to get back to this neutral position. So we need to set the rest curves first. And to do that we need to select all the curves. So we can do that by just clicking and selecting on that group node in the outliner. Then go into the nHair menu and choose Set rest position from current and that means that the neutral state or the rest position is what we see currently.
And again, we needed to do that in case we ever want to get back to this neutral state. Okay. So, now, we can set the Start curves. We can play the simulation through for a few seconds until it's fully in motion that play until about frame 40 or 50 or so. Then, we need to reselect the output curves, because my add dropped us into selecting the follicles, for some reason. So we want to select those output curves. Go back into the nHair menu. And choose Set Start Position from Current, and then when we rewind we don't see any change because frame one has assumed the position of the curves on that frame we were on previously.
So now when we play, it's in motion on frame one. Alright, excellent. And if we ever need to get back to that neutral state we can select the curves and go back in the nHair menu, and choose Set start position from rest, and that would take it back to whatever the rest curve position was. I'm not going to do it this time because we have what we want now. Now the other thing that we need to do is to create an end cache. A cache is basically the simulation stored on disc and we need to do this for numerous reasons.
Most importantly if we fail to create an end cache then it's possible that the simulation might playback differently. During render time, or it might even break completely. Nucleus is quite robust and so the probability of that happening is pretty low. However, we don't want to take any chances. Additionally, if we don't cache the simulation, then our render times are going to be incredibly long because MAYA has to calculate the simulation on every single frame of the batch render.
And it additionally has to calculate all the frames up to the current frame of the Batch Render. Meaning that the render times on each subsequent frame will get longer and longer, and longer. And Maya's actually calculating the same simulation over and over, and over again on every frame. And that's obvious a huge waste of resources of time. so we need to create and end cache. To do that, I want to actually save a new version of my scene file. Because if I did the end cache currently with this scene file name then when you actually try to create the cache, you'll get an error saying that it already exists, so I'm going to actually save my scene out to a new file name.
And you don't need to do this and you actually shouldn't do this, but I have to do it. So I'm going to do File > Save scene as, and I'm going to call this one storing an end cache finished. Again I'm doing this, so that when you do this process, you won't get an error message saying that the cache already exists. Okay, so I've stored my scene file and now I want to create the cache, so this time I actually have to select the hair system not the curves and then going to be nCache menu and choose create new cache Options.
And by default, it's going to do the entire time slider. And I've got 240 frames in my timeline. And you'll see that it's going to store these cache files in a folder called cache in cache and then the scene file name. And that's all of course in the current project. And I'll go ahead and click create and that cache gets calculated. Okay our nCache is finished and now in fact we can actually scrub through the timeline. Which is something that we couldn't do before. And if we play it, it plays back at about the same rate, but that's just because it's loading a lot of information off the disk.
If it were a really lightweight simulation we might actually get real time playback from it. But that's the process of creating an nCache for an nHair system. And this scene is now ready to render. And that's how we can create dynamic fur using nHair. We've really only scratched the surface here. You could attach hair to an animated character and use that to draw fur as well.
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