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Using Particular for drops By Steve Toyama
"Ame, ame, fure, fure..."  Rain, rain, fall, fall.  It's the season for rain in Los Angeles.  While we do have falling leaves here, and other seasonal icons, most Angelenos think of "rain" as a winter season icon.  In this tutorial, Steve Toyama takes you through a procedure to make wet pavement.   In this tutorial we will be creating rain drops falling onto a concrete surface using Trapcode's Particular for Adobe After Effects.

When it first starts raining, raindrops will hit the surface of the dry concrete and create little dark circles which slowly fade out with time. Eventually the entire surface will be wet and we will no longer be able to see them; but let's imagine that this is the first rainy day of the Fall season.

1. Create a new composition in After effects at NTSC DV settings and set the duration at 5 seconds.

click on each image for larger

You can name it anything you like, I'm going to call it "Rain_On_Concrete".
Import the file "concrete01.jpg" into your project window. You can download the file here by opening this image and CTRL-click (right-click) to SaveImage.

2. Create a new solid (command+Y mac, ctrl+Y pc) and make sure its the same size of your composition. You can choose any color you like. For this project I chose a black solid. I'm going to name our solid "rainParticular".

3. Apply Particular to your solid.

Go to the effects pulldown menu and choose Trapcode>Particular.
Scrub through the timeline and you'll notice particles flowing out from the center. This is Particular at default settings.

4. Bring the concrete image into your timeline.

Make sure that the concrete01.jpg image layer is below the Particular layer in the timeline or you won't be able to see the raindrops we're going to create.

5.Bring up Particular settings in the effects controls panel (select the layer and press F3 for effects).

First we're going to adust the emitter settings for Particular. The emitter is where our particles are going to be birthed from.

5a. Change Particles/sec from 100 to 0 as we want our rain to start with a few drops in the beginning and end up with many drops towards the end of our animation. Set a keyframe at the beginning of our comp at 0 and set another keyframe with 100 raindrops at the end of our composition.

5b. Change the emitter type from Point to Sphere.

5c. Set the Velocity, Velocity Random, and Velocity from motion to 0 because we don't want our raindrops to be moving all over the composition.

5d. Change the Emitter Size in X to 2000 and the Emitter Size in Y to 2000 so that Particular will create our Raindrops over our entire comp.We have to create our emitter to be large because if its too small our raindrops will tend to clump up in the center. Change the Emitter Size in Z to 0.

At this point in our composition our raindrops appear randomly across our surface. In addition, they're at Particular's default particle settings so they don't look anything like rain. We'll change that next.

6. Adjust Particle settings.

Here we're going to set up what our particles are going to look like. We're going to try our best to mimic what a raindrop looks like when it hits a dry surface, in this case, dry concrete.

6a. Change Life[sec] to 5 seconds.

6b. Change Life Random [%] to 20.

6c. Change Sphere Feather to 2.0

6d. Change Size to 7.0

6e. Change Size Random [%] to 30.0

6f. Twirl down the arrow for Size over Life. The graph will determine how the size of our particle will change over time. Choose the second box down from the top right to select the preset for linear size reduction over time.

6g. Change the Opacity Random [%] to 20.0

6h. We also want the Opacity of the raindrop to fade over time as the water on the dry concrete will evaporate over time. Twirl down the arrow next to Opacity over Life and choose the same preset as we did with Size over Life.

7. Color over Life

In addition to changing the opacity of the raindrop over time, let's adjust the actual color of the particle over its life. From the pulldown menu of Set Color, choose the option called "Over Life". This will give us an option to choose a gradient over which the particle will get its color information from over time. Create a gradient that starts very dark and ends up light. I chose to start with almost a full black and ended with white. Remember that we adjusted the Opacity settings earlier so we don't have to worry about  white raindrops towards the end of our comp.

8. Nest the Composition

Create a new comp with the exact same settings as our current comp. Bring in our old comp and nest it into the new composition. Delete the old concrete01.jpg image from the first composition and bring it into the new one. You should now have our Rain_On_Concrete Comp as a layer over the concrete01.jpg in our new comp. Turn on the transfer modes for the nested composition and select Soft Light. This will give the drops of rain a translucent quality like water.

9. 3D Layer Property.

Currently our rain is falling straight onto our composition as if we were looking through a flat window facing up. If you look closely at our concrete01.jpg, the photograph was taken with the camera on the x axis turned slightly downwards.

Match the groundplane of the photograph by turning the 3D Layer switch. Rotate the composition on its X axis. I used a rotation of -45 degrees. Scale up the comp to fill the screen and adust its Y position. You should now have the raindrops falling in 3D Space. Don't forget your umbrellas!

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STEVE TOYAMA is a texture & graphic designer, animator, and TA in UCLA's Designer Extension program in Westwood, California. In addition to working on both 2D and 3D projects for several commercial and music video clients, Steve has also done consulting work for video game publishers. In his spare time, you'll find him behind the stick of his XBOX360, DS, PC or Mac video games. He is also a contributing writer for CreativeMac and Consumer Electronics Net Online.
Related Keywords:adobe after effects, trapcode particular, rain tutorial, drops, wet concrete, steve toyama, ko maruyama


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