Let's first take a brief look at emitters since they are the foundation upon which everything in Ripple Rain is built: An emitter consists of a ring silhouette and an emitter profile.

A ring silhouette is the edge on profile of the appearance of a single water ripple. The height of what you draw directly correlates to luminosity information rendered in the final bump map (ie, height drawn = apparent height when rendered).

Since you may want to use Ripple Rain for projects we haven't thought about, we're not going to limit your creativity. We give you the power to draw the silhouette of your ripples.

An emitter profile defines how to use a ripple silhouette. Quite simply, it's when, how fast, how far and how much. Shown below is a complete list of the input parameters:

Number of Rings	An emitter emits rings (or water ripples) in the shape of the silhouette drawn at the top of this dialog. Enter the number of rings you want the emitter to create here.
Number of Frames Between Rings	The number of frames that passes between emissions of rings. Smaller numbers create rings more quickly.
Number of Pixels Radius Grows per Frame	This parameter determines how fast rings move away from the emitter.
Emitter Becomes Active on Frame	An emitter is dormant until its active frame is the current frame. When this happens, the emitter will begin emitting rings. Tip: After you define an emitter and are back at the main screen, you can right click in the layout window to quickly add a new emitter with the same parameters. You’ll be prompted for an active frame number for the new emitter.
Successive Ring Decay Value	When a water ripple is created, the first ring is very pronounced and obvious. Each ring thereafter has a height which is a little bit smaller than the last as the liquid in which the ripple appears is absorbed. The value in this parameter is how much each ring will decay. For example, if you had a ring silhouette which had a height of four and the successive ring decay was set to one, the second ring would have a height of three. The third a height of two and so on.
Radius to Begin Fading	When an emitter becomes active, it begins to emit rings. These rings constantly expand at the rate entered in the "number of pixels grow per frame" parameter. After a while, you’ll want your rings to slowly fade into oblivion. Since Ripple Rain doesn’t know how you plan to use the bump maps created (scale and so forth), you can specify the radius at which a ring begins to fade here.
Number of Units to Fade Pixel Each Frame	Once a ring reaches the value entered in radius to begin fading, the value entered here will gradually decay the bump map’s amplitude to make the ring slowly fade into the surface.

Now that may look like a lot of parameters, but we're not going to leave you in the cold. If Ripple Rain sees a suspicious parameter or parameters clash, you'll see an icon like this:

When you click it, Ripple Rain will alert you of the parameter clash with a screen like the one below:

Let's pretend we just added this emitter to a project we're working on. We'll now go back to the main screen and take a look at some of the other features:

Below, you'll see that our emitter is shown on the right and on the left we see the name of the emitter added. By double clicking the emitter name we get detailed view of that emitter's parameters as shown below. All parameters can be edited, of course.

But what about those emitter profiles we talked about earlier? Isn't that going to create a bunch of ripples that all act the same? That's where variances come in. When you need to quickly add emitters to your project, you just right click in the layout window and specify a new active frame. Even though the newly added emitter may have a different active frame, they may look a bit uniform. By using variances, you can mix up the values of the emitter parameters by entering a variance percentage.

Now if we want to add rain, we just click the rain parameters icon and tell Ripple Rain how we want our rain to look and act when the following screen is presented.

Let’s take a closer look at the rain parameters:

Color	Specify the color of rain by clicking the color. Normally, you’ll want a light gray or white color but we’re not going to restrict you to any one group of colors.
Width	Enter a value from 1 to 5 for the width of your rain drop. If you’re creating an animation which is smaller than a full screen render, it’s possible that rain drops wont appear in the final animation because of the fine detail. Using a wider rain drop will ensure that your rain is visible even in 320x240 animations.
Drop Length	The length of the rain drop. Observe a hard and fast rain and you’ll notice that you don’t see tiny dots of water. You actually are seeing a motion blur of where the water was terminating at where the drop is.
Trail Length	This is an optional parameter that allows you to create a motion blur for your rain completely independent of your 3d rendering package. This parameter is available because some rendering packages may not apply a motion blur to animated textures on stationary objects.
Number of pixels rain travels per frame	The value entered determines how fast your rain moves from the top of a rain plane to the bottom of the rain plane. Typically, you’ll enter a value equal to the resolution height divided by ten or twenty.
Rain Transparency Value	Real rain isn’t a solid color (unless it’s raining paint). It has some transparency to it. You can enter a value from 0 to 255 here. 0 is completely transparent and 255 is completely opaque. Click the preview window to update the view to the current parameters.
Static Trail Transparency	When this option is selected, you can enter a value in the trail transparency parameter.
Gradient Transparency	Selecting this option will create a trail which can best be described as an alpha gradient. It works by taking the rain transparency value and slowly increasing its transparency value in small increments until the final pixel is completely transparent. The increments used are determined by the trail length parameter.
Trail Transparency	If you are using a static trail transparency, you can enter a value from 0 to 255 here. 0 is completely transparent and 255 is completely opaque.

As you can see, you have complete control over rain color, size, movement and transparency. You can even fake a motion blur by defining a trail length and transparency if your rendering package doesn't support motion blur for static objects with animated textures.

Now since rain is generated through animated alpha channeled textures, Ripple Rain has to figure out how many "rain planes" are needed to create the final textures. To simulate rain fall, each emitter is created on its own plane. To minimize the amount of disk space and time it takes to create all these textures, you can place multiple emitters on the same y axis plane. Multiple emitters on the same plane? What a pain in the ass, huh? Not with our Snap to Plane tool. Page back up a few screens and you'll see five grey lines spanning the width of the layout window. That's snap to plane working for ya!

All you do is tell Ripple Rain how many rain planes you want and when you're adding an emitter, it will automatically snap that emitter to the nearest plane. Using more planes creates a more believable effect but also takes more disk space and time to create.

So that's what Ripple Rain is all about. Pretty cool, huh? If you have more questions, don't hesitate to use our online support form to ask us all about it.