Using GridSquares to Create Running Circles
Using GridSquares to Create Running Circles
: Adobe After Effects Tutorials
: Jim Tierney
: Using GridSquares to Create Running Circles
|A CreativeCOW.net After Effects Tutorial
Gridsquares is probably the best of the Geomancy filters to start off with. It's the most like a traditional particle system, and in fact, the only real difference is the use of the grid to control how the particles behave. In this tutorial, Jim Tierney explains the different parameters and helps take the 'fear' out of working with particle systems. You'll need Digital Anarchy's Geomancy filter for this. If you don't have it download the demo.
| What's Up With
This Grid Thing
The grid exists to help you wrangle those particles into going where you want them to. Normal particle systems (say something like Particle Systems II from Final Effects) are very good at letting you define the attributes and behavior of a particle at birth, but aren't so good about giving you control over that particle after it's been born. The grid gives you an extra level of control. Allowing you to set up a structure that the particles have to follow. Of course, you can spew out particles in all directions and ignore the grid almost completely if you want to use GridSquares as a normal particle system.
One thing that seems to overwhelm people is the sheer number of parameters.
Keep in mind that a good many of those parameters are the Randomness parameters.
These don't do anything by themselves. If you eliminate the Randomness
parameters, Gridsquares doesn't have many more controls than something
like Foam or other particle systems. The Randomness parameters are only
there to help you vary the values of the parameter they are associated
with. Let's take the LifeSpan parameter as an example. If it's set to
60, all particles created will exist on the screen for 60 frames, they'll
be born and then die 60 frames later. If you set the LifeSpan Randomness
to 50%, the particles will get a random LifeSpan between 30 and 90 frames
(60 +/- (60 x 50%)). This is great for allowing you to easily adding a
little chaos to your animation, without having to set keyframes and without
giving up the control of the overall animation that the grid gives you.
So if we start off LifeSpan with an original value of 60, this is the
chart we get:
|LifeSpan Randomness Value
||Range of LifeSpan value
||All particles have a value of 60
||54 to 66
||30 to 90
||0 to 120
So, in this case, one particle would be born with a life span of 35, another
with 78, another with 89, another with 47, etc., etc. Adjusting the Randomness
up or down will give you exact control over how much variance you want
to see. It's a essentially a built in Wiggler for every parameter. Convenient,
but it does make the filter look a bit more daunting than it is.
|How's This Here
Grid Work Anyways?
Well, the first thing to know is that it's not really the grid we're working
with, it's the empty spaces in the grid. If you look at the grid (Click
the 'Show Grid' checkbox in the Grid Setup section), you'll see a bunch
of red lines showing you the rows and columns. This is great, but the
empty space between the rows and columns is what matters. This is where
your particles will be created. This differs from the other two filters,
which use where the red lines... but we don't care about that right now
By default, particles can only be created in the empty spaces between
the lines (you can change that and we'll talk about how a bit later).
Just look at the grid and everywhere you see an empty space, that's a
potential location for a particle. If you change the rows to 3 notice
how the empty spaces get bigger. That's great, but that means there's
less places for particles to be created and making the empty spaces bigger
will not increase the size of your particles. Particles have their own
size control and the grid spacing won't affect them.
just remember that every where there's an empty space, that's a POTENTIAL
location for a particle to be created. That doesn't mean a particle WILL
be created there, just that it's possible. Whether a particle is created
in any given location is a result of where the Producer Point is and we'll
talk about that next. Also keep in mind that once a particle is created
it can move all over the grid, unless you set it up so that it won't (set
speed to 0, constrain it to the horizontal and vertical axis', etc).
And The Producer Point
Let's get moving on this tutorial. We can talk about the producer point
as we get things setup. Here's an example of what we're going to do. This
is what you should have at the end of this. At the very end, we'll adjust
a couple things and do some alternative endings, but basically, this is
what we're shooting for.
Click on the image to see the movie (300K).
back to the Grid section and let's set our foundation up. Set the Grid
Height to 100, set the Grid Width to 640, set Rows to 3, and Columns to
20. As you'll notice from the movie above, we want the circles to go across
the screen in a thin band. There's no need to have the grid bigger than
the band, since the circles won't be moving around. So we've set the grid
dimensions to the exact size we wanted the band. Since we wanted 3 rows
of circles, we've set the grid to have 3 rows. As you'll see shortly,
we could set the grid to have more rows and use the Producer Point to
limit where the circles get created, but again, since the circles won't
be moving around just making the grid have 3 rows is the easiest way to
go about it.
The thing to keep in mind if the particles were moving, is that they are
only visible on the grid. If the particles go off the edge of the grid
they disappear. So there will be plenty of times where you'll want a grid
with plenty of extra space around where the particles are being created.
If the particles were moving we'd have a larger Grid Height and more rows,
to let them have room to move around and remain visible.
The Producer Point controls where the particles get created. If it's really
small, all the particles will be created in a single grid space (the empty
space between the rows and columns) and will appear to come from a single
point. The larger the producer point, the more grid spaces it'll cover,
and the wider the area that particles will appear in.
In this case we want particles to be produced all across the height of
the grid, but only in a very narrow section of the grid horizontally.
Imagine a radar screen with the bright line revolving around it. We want
the producer point to be that bright line. Leaving a trail of particles
behind it, but only creating particles along the line.
Take a look at the difference between these two images, one with a thin
producer point the other with a large one:
Producer Point = 30
Point = 300
Twirl down the arrow for the Producer Point section and set the Height
to 100 and the Width to 20. This gives us a tall, thin producer point.
As the producer point moves across the screen it'll create particles.
This way particles will slowly appear across the screen. Old ones will
then slowly fade off.
If our grid was larger than 100 pixels in height, the particles would
still only be created in the 3 rows that the producer point occupies as
it crosses the screen. This is caused by the fact that the ppoint is still
only 100 pixels high, even though the grid is larger. While this isn't
important in this case, since the grid is going to remain 100 pixels high,
it's still worth illustrating:
|ppoint = 100, grid = 100
||ppoint = 100, grid = 480
Ok, so now we have a grid that's 100 pixels high and a ppoint that is
also 100 pixels high. Let's get particles going across the screen by animating
the ppoint. At time 00:00 set the producer point value to 10,320. Move
the time marker to 04:00 and set a value of 630, 320.
If you play the animation back now, you'll see that our particles are
indeed created as the ppoint moves across the screen. Unfortunately, they
don't stay put, and they're all sorts of different sizes.. They're flying
around and flying off the edge of the grid. Now you can why you sometimes
may want the grid larger than the ppoint.
||Particles flying off the grid. Not what we want in this case.
However, in this case we don't want the particles flying around anywhere
and we also don't want them all sorts of different sizes.. and we'll deal
with that in a second. Before we deal with that, twirl down the Square
Square Setup is where you set what shape you want to use, where you set
up the outlines, set the direction, and set up a few other things. One
of those other things is the Grid Unit, which I'm not going to cover here,
but make sure you read the manual before changing it.
In this case we want circles instead of squares, so set the Shape pop-up
to 32-sided polygon. This creates circular shapes, which works really
well for small to medium sized circles. If you want really large circles,
go with the 64-sided polygons. While these will appear smoother at larger
sizes, the 32-sided polys will render faster.
Since we don't want the outlines on, deselect the Outlines checkbox. That's
all we need to do here, so close the Square Setup section.
At this point let's set up the colors that we want the circles to be.
Go down to the Color section and twirl open that section.
Change the black color chip to match the blue color chip. Now turn off
Colors 2 & 3. This will create a gradient that goes from red to blue.
The circles will get their colors from this gradient.
Also, change the transfer mode to 'In Front'. This will cause any circle
that gets created in the same grid space to be rendered on top of the
one that's already there. If you just leave it at 'Normal' the circles
will blend together and create other colors or add together to create
white. 'In Front' is really cool and useful transfer mode. I mean, it's
tough to get excited about a transfer mode, but this is pretty useful,
so if you're going to get excited about a transfer mode, this is it.
Here's how the color parameters should look:
Open up the Square Attributes section (twirl down the arrow next to it).
We need to tell GridSquares what we want the particles to look like and
how we want them to behave. For the most part, this is accomplished in
the attributes section. Since we want them to stay still, set the Speed
to 0.0. This will prevent the particles from moving once they're created.
Speed controls how fast they move in a given direction once, they're created.
Obviously, with a speed of zero, they're parked at home and ain't going
Next, let's make sure all the particles have a nice uniform size. Set
the Minimum and Maximum Width to 20 and do the same for Minimum and Maximum
Height. What's up with the Min/Max controls? A little further down you'll
notice the Horizontal and Vertical Growth Speed. If the Min and Max are
different, the Growth Speed controls how fast they grow from the Min size
to the Max. However, with Min and Max set to the same size, there's no
room to grow, so the Growth Speed is ignored.
Usually, if the Min Width was set to something like 5, and the Max Width
was set to 20, the particles would grow from 5 pixels wide to 20 pixels
wide. With them both set to 20, all particles start off and end up at
So, at this point, our parameters look like this:
The screen should look like this:
Now that we've got all that set up, let's do a few last tweaks.
If you play back the animation now, you'll notice that there are grid
spaces that don't get filled up. We can usually solve that problem by
cranking up the Birth Rate a little. Set Birth Rate to 3. This will cause
3 particles to be created every frame and should solve the problem. The
more particles being created, the more likely one will be created in every
grid space. Since the particles are random, there's no way to guarantee
that they'll fill every space, unless you have enough of them being created.
The particles at the end of the stream (the ones that were created first)
all seem to fade out evenly. This is ok, but we really want things to
look a bit more 'organic' and have them fading out somewhat randomly.
To get them to do this, set LifeSpan Randomness to 15. This will varying
the LifeSpan just a little bit. For the most part, we want them living
for 60 frames, but it'd be better if they randomly got a LifeSpan between
say, 50 and 70. By changing the randomness parameter we allow that to
happen automatically, without having to set any keyframes. There you have
it... better living through plug-ins. ;-)
Now set Fade Out to 10 and Fade Out Randomness to 65. This will further
vary the tail of particles. Fade Out is the number of frames that the
particles fades out over when it dies off. By giving it a randomness of
65, we create a pretty wide range of possible values that each particle
will get. Some will fade out over 3 frames, some over 16. Effectively
causing much more randomness in how long each particle is on screen.
All this should give you an image that looks like this:
That finishes off this tutorial. I hope you have a better understanding of how this stuff works. If you have any questions feel free to email me at email@example.com.
Jim Tierney is the creator of Digital Anarchy and has worked on some of the most widely known and respected After Effects plug-in packages out there. Starting at MetaCreations, with Final Effects, and moving on to Atomic Power and their Evolution and Psunami packages . He also worked for Cycore for awhile, but was primarily involved with their 3D software and only remotely involved with Cult Effects. You can visit Jim's website by clicking on his logo to the right.
Please feel free to come to the Adobe After Effects Cow to discuss this technique or others. Or drop into Jim's own Digital Anarchy Forum here at the COW. Jim Tierney is a frequent visitor and contributor.
If you've found this tutorial from a direct link outside our site, please drop by CreativeCOW for a visit. We hope you'll make it your new home.
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