Second Stage: Wind Simulations
Now I want to simulate some wind effecting the grass and for that I can use some different techniques. Here I will explain the animation attributes from the paint effects stroke settings, but we can use control curves and make it react to field forces from the dynamics system in Maya 7, or you can turn it into polygons and then make it soft bodies and make it react to forces as well, but here I will show the stroke settings for the animation in the paint effects system
In this image you can see the tree mayor animation sections for paint effects, the first one is the Behavior sections, which will have the subsections of displacement, forces, turbulence, spiral, and bend. The second is the Gaps section and the third one is the Flow Animation section.
These are the settings made to control a lot of the aspects for the animation behavior, but you have to know that you can set keys in every single panel, from shading to number of branches, you can animate almost everything, so be creative, there's no limitation. I will show you some examples of that in the tree growing simulation.
Well, first I will explain the settings from the Behavior section and then I will show you how to configure this settings for our grass wind simulation. The Behavior panel is inside the creation panel.
Here we are going to start exploring the Turbulence panel, here is the image.
You can find this section in Tubes > Behavior > Turbulence.
We have some really interesting settings. First we can choose our force type, this will let us to create the kind of force we need, for example the local force is better for animating individual objects, and the word force is better is we want to share our forces in another brushes. I will go and use the 'Grass Wind' type. This kind of force makes more turbulence and effects the tip of the tubes and has less effect on the roots of the tubes. Creating some really nice wind simulation.
Then we can choose the interpolation that the mathematical method used to smooth the motion in the animation.
, defines the air speed due to turbulence.
, defines the amount of variance in the turbulence.
, defines how quickly the turbulence changes over time.
, offsets the position of the turbulence
These are the general settings for the turbulence section, working with this settings we can get some really nice simulations, now back to our scene, here are the settings I will use for my wind simulation in the grass.
As you can see in my settings, I already have some keys added to this section, so let explore this settings. I will use wind turbulence and smooth over time and space for may initial settings, so I went to frame 1 and set a key for 'turbulence', Frequency', and 'Turbulence Speed', and this will be a soft wind animation. I use really low values, like 0.16 for 'turbulence' and 'Frequency', and some really low values too for 'Turbulence Speed', maybe some between 0.3 to 0.5. Then go to frame 300 and set keys again, this time with some 'high' values, but again this is a wind simulation and is kind of soft so I will use maybe some settings around 0.2 in 'turbulence' and 'Frequency', and set the 'Turbulence Speed' a bit higher too.
This is really simple for teaching reasons but, for a realistic simulation you will need to introduce some more keys and use a lot of different values in order to have a rich scale of movement and deformation, and to simulate the behavior you need. This always will be different, for a nice day or a stormy wind, you need to explore a lot of the settings and search for what you want to simulate.
Another thing is that you can control the curves of this animation in the Graph Editor.
I will use two kinds of grass, and I will animate the second grass in the same way I animate the first one, but I will use a different values to have more randomness and movements. You can see I actually did a little bit of the work, but these simple settings I use to simulate, is a great way for the wind forces. Of course in order to have more control you have the entire panel of behavior to explore, here I am using only turbulence, but you can animate and use Displacement, Forces, Bend and Spiral not only to animate, you can use this sections to help to construct the shape of you paint effects and created more rich forms and nice deformations.
In this scene I created a forest in the background and I use the same method to animate this, you can see that it is exaggerated a lot but you can see it's actually moving, it's the same Turbulence animation but this time I use 'the tree Wind' type, and really low values, kind of 0.021 because this type of turbulence is a little more stronger and you whatto apply more turbulence to the branches, so it's simulating the real tree wind deformations. For this I use the Oak Forest stroke As you will see this kind of stroke has no branches but again, I use 'the tree Wind' type for teaching reasons.