Tutorial 2


In the first tutorial we made an emitter move between a few points on the stage, but only in a straight line. What if we want the emitter to follow a more complex curved path?

To pick up where we left off, load the project that you saved at the end of the first tutorial. Select Open from the File menu, click the OPEN button on the main toolbar, or select the filename from the list of “most recently used” filenames on the File menu.

Now let’s make a curve. R-click on the middle position key in the stage window (the one at frame 30). The following context menu is displayed:



For now ignore all of the other menu functions except for the Curved item. Click the Curved item to convert the position key from a linear key to a curved or “spline” key.

There are three indications that a key is curved: 1) The path is now visibly curved on the stage; 2) R-click on the emitter again – the Curved item is now checked. 3) There are two spline control handles visible.



These control handles can be clicked and dragged to change the curve of this key. Click on one of the controls (the small points at the ends of the dotted line) and drag it around. You can see that the controls move together when one of them is dragged – this is due to the fact that they are Connected by default. If you R-click on the handle or the position key, the Connected menu item is now checked. If you select the Connected item, the control points become disconnected, and no longer move together.

You’ll notice that once you disconnect the control points the Connected menu item is no longer enabled. How do you make the controls Connected again? You need to toggle the key linear (non-Curved), then back to Curved again.

There are shortcuts to the Curved and Connected functions that do not require the use of the context (R-click) menus. If you Alt-Click (hold down the Alt key while L-clicking) on a position key, it will toggle between linear and curved. Similarly if you Alt-Click on a control handle, it will change from connected to disconnected. (Remember that once it is disconnected, the only way to get it Connected again is to toggle it linear then Curved again.)

Make sure the middle position key (the one at frame 30) is Curved and move it around. Notice that the path segments between the first and last position keys “followed” the key you were moving? Not sure what that means? Change the position key at frame 1 to Curved (so now there are two position keys that are curved). Now move the frame 30 position key again. Notice the difference in the way that the path segment between the first key and the key you’re moving behaves?

       

The image on the left is with the first position key Curved and the image on the right is with the first position key linear (non-Curved).

Easy does it!

Let’s go back to linear keys for a minute. If you look at the frame positions (dots) between two linear keys, you’ll see that they are equally spaced. That is, the emitter moves the same amount at each frame. What if you want the emitter to start moving slowly, then move more quickly? (Some applications refer to this as “ease in/ease out”, or as acceleration.) In particleIllusion there is no specific setting to accomplish this – but you can get the same results in some cases. How? By changing the keys to Curved, and adjusting the spline control handles to get the frame spacing you want.

Start by reloading the same project file you loaded at the start of this tutorial. Change the first and second position keys to Curved. Make the control handles of the second position key Disconnected. Now move the control point for the first key so it is approximately on the line between the first and second position keys, and is about 1/3 of the way between the two. Do the same for the spline control of the second key. The result should be a very close approximation of a linear segment between the keys (as if they were both non-Curved).



Now to get the evenly-spaced dots the way we want them (closer together near the first key, and farther apart near the second key) we just need to drag the control point for the first key closer to the first key, and the control point for the second key farther from the second key. Here’s one way it could look:



So it’s possible to approximate the acceleration that we wanted. Note that this will only work in certain cases.


Okay, so now we know how to make an emitter move both linearly and along a curved path. What if we need to make precise adjustments to a position key, for instance if it is slightly out of position from where we want it to be? That’s where we use the Nudge buttons (on the nudge toolbar):



Clicking one of the Nudge buttons moves the emitter one pixel in the direction the button indicates. Note that this is another way (besides dragging or using Move) to move an emitter. Remember that whenever an emitter is moved (even if only one pixel) and it is not at a position key, a position key will be created. You can also use the key shortcuts of Shift+arrow keys; to nudge up, use Shift+Up Arrow for example.

If you need to create a position key at the exact spot that an emitter is currently at – don't try to use Move or drag the emitter. Use NUDGE instead (you can Nudge the emitter up then down and it will be at the same position, but a position key will have been created for it).

Let’s say we’ve just spent quite a bit of time adding position keys, moving them, nudging them and adjusting them until they were just right. Now we’ve realized that we’d like the entire path of the emitter to move some amount – we want the path to keep it’s same shape, but want it to start at a different location. It would take too much effort to move each individual position key, so what can we do? The solution is simple: hold down the CTRL key while you click and drag the emitter. This will move the entire emitter path without creating any position keys.

Note: you might find that turning off Show Particles before using this trick makes things more responsive and therefore easier to position.

There may be a time when you don’t need precise placement and movement of an emitter. Perhaps you want some sparkles moving around a logo, or just want to play around a little. You certainly don’t want to take the time to set up a spline path for the emitter, so what do you do?

Start a new project by clicking the New button on the main toolbar:



You can also use the key shortcut of Ctrl+N, or select New from the File menu. If your existing project hasn’t been saved, you will be asked if you want to save the project first. Then the project will be reset to its default state (the stage will be cleared). Now add an emitter to the stage, R-Click on the emitter on the stage, and select Record Position. A message box is displayed letting us know what is about to happen:

     

After we click OK, we position the mouse cursor where we want the emitter to start, then click the Left mouse button. Playback will start and the mouse position will be sampled at each frame, with a position key being created at each frame. Use the mouse to “draw” the emitter position path on the stage, then click the Left mouse button again to stop playback. Note that playback will also stop when the project end frame is reached.

After position recording has stopped, a dialog box will be shown with a slider control that is used to smooth the position keys that were created.



Move the dialog away from the stage and adjust the slider, noting the effect on the emitter path on the stage.

If you made quick movements while recording position, then you’ll probably want to use very little or no smoothing. If you made a slow curving path, you may want to use more smoothing.

Note that when you use the Record Position function, all position keys following the frame at which you started recording are deleted and replaced with the recorded position keys. Also, Record Position only works for emitters, not deflectors, blockers, or forces.


Undo what you do

Suppose while you were trying that last trick of moving the entire emitter path (by holding the Ctrl key) you released the key too early, and ended up creating a position key when you didn’t want to. How can you get rid of that key you just created? There are a few ways to do it.

One of them is to just delete the key from the stage. With the emitter at the position key, press Ctrl+D. This will delete the position key. Note that if you press Ctrl+D when the emitter is not at a frame that contains a position key, nothing will happen. Also, you can’t delete the first position key (every stage object has a position key at frame 1).

There is also a way to delete a position key using the graph window, but we’ll cover that later when we talk about the graph window in depth.

The most “universal” way of fixing any mistakes you make (such as creating a position key that is not wanted) is to use the Undo function. Most applications include some sort of Undo, so the concept is probably not new to you. If you are not familiar with Undo, it simply reverses the last change or changes that you made. There is usually a Redo function that goes along with Undo, which restores the change – essentially an Undo of the Undo.

particleIllusion supports multiple Undo/Redo actions. To Undo, select Undo from the Edit menu, use the keyboard shortcut of Ctrl+Z, or click the Undo button on the toolbar:

Do it now and see what happens to the emitter on the stage. Undo a few times in a row and you’ll see the last changes you made being reversed. Ok, now try Redo. Select Redo from the Edit menu, or Ctrl+Y, or click the Redo button. Redo until you can Redo no more.

Only changes made to the stage or to the graph window can be Undone in particleIllusion.

When you use Undo, Redo is available until you make some new change to the project. The new change “overwrites” the actions that were Undone, making them no longer available for Redo. A little example to illustrate this. Let’s start a new project (click the New toolbar button or use Ctrl+N.

(Note that you can’t Undo New, just as you can’t Undo Open or Save.)

So we now have a clear stage. Select the "Star Trail 2" library emitter again and add it anywhere on the stage. Now move the emitter to another location on the stage (still at frame 1). Now jump to frame 20 and move the emitter somewhere else on the stage.

At this point we have three actions that can be Undone: 1) Adding an emitter to the stage 2) Moving the emitter 3) Moving the emitter and creating a position key. You should be able to use Undo three times, and end up with an empty stage again. You can Redo three times as well to get all of the changes back. Use Redo until all changes are back. Now Undo just one time – you should have the emitter at a single position on the stage.

Now just L-click somewhere else on the stage (not on the emitter) to add a second emitter. Our list of Undoable actions has just changed. It is now: 1) Adding an emitter to the stage 2) Moving the emitter 3) Adding a second emitter. Use Undo and Redo to see that the action of moving the first emitter to create a position key is no longer available. It has been overwritten by the action of adding the second emitter.

By default particleIllusion is set to keep 20 actions in the Undo list. If you want to be able to Undo more actions, you can change this number in the Preferences dialog (which we’ll talk about in a later tutorial). Note that setting this value higher requires more memory.


Project Settings

We’re about to start digging into the “guts” of an emitter, but before we do let’s take a look at something completely different: the Project Settings dialog.

Click on the Project Settings button of the main toolbar (or use the key shortcut of Alt+P):



This will open the Project Settings dialog:



Here you see the settings for Motion Blur (which we discuss shortly), output frame rate for the project, background color for the stage and preview window, stage size, and several other options.

The frame rate value determines how many frames per second particleIllusion will display for playback and when saving output. Important: some emitters look quite different at different frame rates. Therefore, it is important to set the frame rate before you start doing any work on the stage with emitters, or you may not get the results you want.

A note about frame rates. The windows that animate (the stage during playback, and the preview window when displaying a library emitter) will attempt to match the project frame rate. In many cases, the actual frame rate may be lower than the project frame rate. The status bar at the bottom of the particleIllusion window displays the achieved frame rate followed by the project frame rate in parentheses.



The achieved frame rate is determined by the speed of your computer, the presence of 3D video hardware, the number of particles, and (especially without supported 3D hardware) the size of the particles being drawn. There are other factors involved too, but they involve things that we have not covered yet (the presence of deflectors, blockers, and background images all have an effect on playback speed).

The color setting shows the current color of the background of the stage (and preview window if desired). To change the color, just click on the color box and a color chooser dialog will be shown:



You can select the color by clicking and dragging in the two color windows, or by entering the color component values directly. There is also a button that looks like an "eyedropper" -- click this to sample the color from anywhere within particleIllusion.

A note about background color: some particles (flagged as “intense” which will be covered later) look best on black backgrounds.

The Don't erase option has a dramatic effect on your project. When checked, the stage window will not be erased before a new frame is drawn. The result is that each particle leaves a "trail", as if it's painting itself onto the stage. You can acheive some beautiful organic and artistic effects using this option, but it doesn't work under all conditions. Don't erase will not work when you are using background images or when using High-quality motion blur (neither of which we have covered yet in these tutorials). Also, Don't erase only works during playback.

The Stage Size settings determine the size of the stage, which is the area that will be saved when saving output, and is the only area that displays particles.



The drop-down list shows several common stage sizes. You can also directly enter the width and height values. If there is a stage size that you would like to add to the drop-down list, enter the values for width and height, then click the Add button (button with a "+" on it). If there is a stage size in the list that you will never use and want to delete, first select it from the list, then click the Delete button (button with an "x" on it).

The Aspect Overlays section allows you to "mask off" parts of the stage window that will not be visible in the final version of your output. This is most useful for film work, where parts of the original frames will never be seen on the screen; the overlays let you see what parts of the frame will not be visible.



Two different overlays can be defined and displayed: A and B. To turn display of an overlay on, check the ratio option, then select the aspect ratio to use. You can select a value from the drop-down list, or type a custom value into the box. The overlay is drawn semi-transparently in the stage window, and you can set the color of the overlay by clicking the color box at the right. A few standard options ("Full Frame", "Academy", etc.) are defined, and can be selected. Note that selecting certain options will change the ratio value of Overlay A. The final control in this section is the Y offset value. You can use this to shift the overlays up by entering a positive value, and shift them down by entering a negative value (using the up/down buttons to the right of the number box).

Similar to the Aspect Overlays is the Safe Areas display:



When selected, title safe and action safe areas are indicated in the stage. As with the aspect overlays, you can set the color of the safe area displays by clicking the color box. You don't need to open the Project Settings dialog in order to turn display of the aspect overlays and safe areas on or off. You can use key shortcuts of Ctrl+Shift+A and Ctrl+Shift+B to toggle overlays A and B, and Ctrl+Shift+S to toggle display of safe areas.




The Field Rendering section of the Project Settings dialog lets you create "field rendered" (or "interlaced") output.



With Off selected, field rendering is disabled. To turn on field rendering, select either the Upper first or Lower first options. Which you should choose is based on the video system that will be displaying the final output.

 

Field rendering is useful where the final display medium is interlaced, such as broadcast television in many countries. Although the output has horizontal lines through parts of it when viewed on a computer monitor (the right image above), when displayed on the correct equipment the display will be much smoother than an image produced with no field rendering displayed on the same equipment. This is especially true with fast-moving particles.


There are a few buttons located under the Cancel button of the Project Settings dialog:



The Save and Load buttons are used to save and load the Project Settings. This can be useful if you have a few "standard" settings that you need to switch between, or if you want to make sure that several computers all use the same Project Settings.

You can also view or edit the Project Notes using the Notes button. The Project Notes are a great place to store information about the project, and can hold quite a bit of text. (The Project Notes are also accessible from the main View menu.)

The last button is the Memory Usage button, shown as "Mem.". Click this button to get the OpenGL texture memory usage information:



You will normally not be concerned with memory usage when using particleIllusion. If you start experiencing problems (random crashes, sudden slow-downs, etc.) memory usage might be an issue.


The Motion Blur options that we skipped earlier can be used to add more realism to animation. If you’ve ever seen a photograph of something that is moving quickly, you know that the image appears blurred. Fast-moving objects whether on film or viewed with the naked eye are usually not sharp – they are blurred. Because we understand this fact, fast-moving particles in particleIllusion should also blur in order to look more realistic.

Start a NEW project and add the "Super Whirls 01b (mb)" emitter to the stage (it's in the "Group 5" folder). To add motion blur to the project, simply check the Enable box in the motion blur options section of the Project Settings dialog. We’ll see a few more options appear, but for now just click OK to close the dialog.



Now start playback to see the effect of motion blur on the particles:

     

Even from these still images, you get the sense that the particles in the right image are moving more than the particles in the left image. Now let's go back to the motion blur settings in the project settings dialog and see what they all do.

Preview: Motion blur (when enabled) will always be shown while playback is occurring, but the Preview option is used to display motion blur on the stage when playback is not occurring (as long as "show particles" is active). Note that turning on motion blur preview may slow down stage redraws.

Regular and High-quality: You can choose between these two methods of motion blur calculation. When using Regular motion blur with particles that have very low visibility, "banding" artifacts can occur:

       

High-quality blur will correct this problem, but since the High-quality method uses an OpenGL feature that is not hardware-accelerated on most graphics cards, it will probably be much slower than Regular motion blur. For that reason it is recommended to use High-quality motion blur only when using Regular blur gives unwanted visual artifacts.

Extra Frames is the number of frames that are averaged to produce the blur effect – the higher the number the smoother the blur, but the more time it takes to draw them.

Blur amount controls the amount of the frame over which the blur occurs. When set to 100%, the particles are blurred over the entire interval between the current frame and the next one. If set to 50%, the particles are blurred over only the first half of the interval between the current frame and the next one.

Intensity Adjust: When particles flagged as “intense” (covered later) are motion blurred (with Regular blur), the result may be a change in intensity of these particles. The Intensity Adjust slider is used as an additional scale factor to be applied to the visibility of “intense” particles only in order to help counteract this intensity change due to blurring.




Emitter and Particle Type Properties

Okay, now we’ll start digging in to the “guts” of emitters and look at the properties that determine how they act, and also how the particles they emit will look and behave.

Clear the stage using the New button. Now select the "Heavy Fire Sparkles" emitter. Add a single emitter anywhere on the stage. Make sure Show Particles is on and jump to frame 30. Now turn your attention to the Hierarchy window:



From this we can see that there is a single layer in the project (we’ll cover layers in a later tutorial), there is a single emitter on the layer called “Heavy Fire Sparkles 1”, and this emitter has a single Particle Type called “fiery”.

(When emitters are added to the stage, they will be given a name that is the library emitter name plus a number. This is to try and keep things straight when more than one emitter is on the stage. You can rename the emitter to something more meaningful to the project by clicking on the emitter name in the Hierarchy Window.)

Remember that emitters are made up of one or more particle types, and the particles that this emitter will emit are based on the settings of those particle types.

We won’t cover them in depth here, but let’s take a quick look at the particle type properties. Either double-click the “fiery” particle type or L-click on the little plus sign to the left of the work “fiery”. Now you should see all of the particle type properties. What’s important to note right now is that some of the particle type properties (the ones with the cyan and purple icons) have the same names as some of the emitter properties. The emitter properties (life for example) are a global “scale factor” that applies to the life settings of each of the particle types in the emitter. We’ll discuss this in depth in the next tutorial.

Okay, forget about the particle type properties for now. Now we’ll see how the hierarchy window and graph window work together. Click on Heavy Fire Sparkles 1 in the hierarchy. Now look at the graph window. It should show:



Jump to frame 30 and drag the emitter to another point on the stage. You should now see a second position key in the graph window:



This should all be familiar from the earlier examples. Now something new. Suppose we wanted that position key to be at frame 40 instead of frame 30. One way to do that would be to Undo, then jump to frame 40, then move the emitter again. An easier way is to use the graph window. Just L-click on the position key at frame 30 (in the graph window) and drag it until it is at frame 40. That’s it. You’ll notice the stage change as well when you make this change – the density of the dots on the path segment will change because you are changing the number of frames over which the position of the emitter changes.

If you had a motion path of 2 segments (let’s say the one key is at frame 30 and the other is at frame 60) but the distance moved in the second segment was much smaller than in the first segment, the emitter would move more quickly over the first segment, then more slowly over the second. What if you want the emitter to move at the same speed over both segments? You can approximate this by dragging the middle position key in the graph window until the dots in both segments (looking at the stage) appear to have the same spacing.

Note that when the position keys are being displayed in the graph window, the graph is titled “Position” with the current position value, and the graph is shown as a horizontal line graph. If you click on the graph, nothing happens. The position graph is a special case – position keys are added via the stage, not using the graph. Let’s look at the graphs of some other properties.

Select the emitter Size property in the hierarchy window, and jump to frame 30:



You can see that the size graph is a horizontal line with a Y-value of 100%. What does this mean? Since this emitter size graph is a scale factor that is applied to all of the particle types it contains, this example shows that the size of the particles will be 100% of whatever size they were set to in the particle type size property.



(Since the line is horizontal, we can also tell that the size value remains constant over all frames – more on this shortly.)

Now L-click on the red point in the graph window and drag it up and down. While you’re dragging it, notice the effect it has on the particles on the stage – they’re getting bigger and smaller. Okay, now drag it to about 100% again.

L-click in the graph window at about frame 60. You’ll see that a new graph point has been created. This is a key frame, very similar to the position keys that we’ve already created. The difference is that this key is a data key instead of a position key since a data value (size) is changing instead of position. Data key is the generic term for these keys created in the graph window – we’ll refer to them more specifically as the type of data they represent. In this case the key will be called a size key. As with position keys, at least one data key will exist for each property, and it will usually be at frame 1.

So now you should have a graph with two size keys (points) on it. Drag the second key so it is at frame 60 with a value of about 10%. Drag the current frame indicator so you can see what happens as the frames increase. What you should see is the particles eventually getting smaller and smaller. Important: Graphs that show frame numbers along the X-axis show values of properties for the particle at the moment the particle is created. They say nothing about what an individual particle will do over time.

In our example, particles created at frame 1 will have a size scale of 100%. Particles that are created at frame 60 will have a size scale of 10%. Particles that were created at frame 1 that may still be around at frame 60 still have a size scale of about 100%. Understand? Most of the graphs of emitter and particle type properties represent the values at the time the particle is created only. The only exception to this is the particle type graphs of properties "over life”. We’ll discuss that when we get into the particle type properties.

Okay, just click in the graph window and create a few more size keys – you can position them wherever you want.



The data key that is red is the selected data key, which will be important in a minute. Right now just L-click a data key and drag it left and right. Notice that it can’t be dragged past any neighboring keys. Also note that the first data key is fixed at frame 1.

Now why is one key selected (red)? Select any key except the first and then R-click anywhere in the graph window. You’ll see this menu:



Select the Delete menu item. The selected key has been deleted (remember that you can Undo changes made to the graph window).

Now if you r-click on a data key instead of in an empty area of the graph window, you'll see that the Curved menu item is now available:



Select Curved and you'll convert the data key to a "curved" key -- just like we did in the last tutorial with position keys. You can also Alt+click on the data key to convert it between a curved and non-curved key. The control handles work just as they did in the stage with position keys, so curve a few of the keys:



Note that if you find yourself using curved data keys almost exclusively, you can change the particleIllusion preferences so that curved keys are created by default. We'll cover preferences in a later tutorial.

What do the other menu items do? Detailed graphs displays the selected emitter, free emitter, or particle type name in addition to the property selected and current value:





Detailed titles can help you keep better track of which property is displayed in the graph window, especially when a project contains several complex emitters.

Reset simply deletes ALL keys from the graph (except the first), and sets the first key to a default value. An interesting thing about using Reset when the position graph is being displayed – Reset causes all of the emitter position keys (except the first) to be deleted, but it also positions the emitter in the exact center of the stage.

The Scale function displays the following dialog:



This function allows you to either compress or expand the values or frames of the graph. For example if we wanted to double the values of each key of the graph we would select Scale Values (y), set the scale factor to 200% and click OK. If we wanted the changes to occur over a shorter number of frames (compress the time) we would select Scale Frames (x) and enter an appropriate scale factor – we’d use 50% to make the changes occur in half the length of time. (Note that only Values OR Frames are scaled when the OK button is pressed. Selecting Values and setting a scale factor then selecting Frames and setting a different scale factor then pressing OK scales the frames only.)

The Zoom menu function allows you to interactively zoom in or out either Y (values) or X (frames). Zooming out allows you to see more of the graph, while zooming in is useful for more precise positioning:



As you change the sliders, you'll see the graph window update to the new zoom level(s). Note that you can also use the key shortcut of Alt+Z to activate the graph window zoom function.


The Reference menu function allows you to create a visible copy of the graph so you can coordinate the graphs of other properties to the graph of the referenced property. Let’s look at an example. With the current size graph selected, R-click and select Reference, then Create A. Then in the hierarchy window select emitter Velocity.



There are two reference graphs available, A and B. If a reference graph has been created, it can be toggled on/off using the Show A (or Show B depending on which graph you’re interested in) function. When a reference graph has been created it will be displayed in either light purple (A) or light green (B) and its title will show in the upper right corner of the graph window.

In our example you can see the size graph drawn as Reference A, and the velocity graph as the current graph. Now it will be a lot easier to coordinate changes in velocity to changes in size.

Note that the reference graph is just a snapshot image of the graph. If we were to go back and change the size graph, the reference graph we created from the size graph would not change.

Here’s a quick summary of the graph window. For the majority of graphs (except for position) you create a data key by clicking in the graph. You can drag data keys around, and can delete keys. You can zoom the graph, and create reference graphs. You can also scale the values or frame numbers of the data keys in a graph.

Moving Multiple Keys

What if you want to move more than one data key at a time? You can’t select more than one data key at a time in particleIllusion, but it is possible to move all of the keys in a graph at once. To do this, hold the Ctrl key before clicking and dragging a key. The mouse cursor will display the word “all” so you’ll know that you’re moving all of the data keys. Now just drag as usual. Once you’ve clicked, you no longer need to hold the Ctrl key.

One other thing to point out about the graph window that you may have already noticed. When dragging a data key, the window will scroll automatically when you reach its edge. Obviously, you can also use the scroll bars to scroll the window.


Back to the Hierarchy

Now that we know how the graph window works, let’s take a look at some of the things it will show. We’ll end this tutorial with the emitter properties that are available in the hierarchy window, and start the next tutorial with an examination of the rest of the emitter properties and the particle type properties.

The first group of properties are the emitter scale factors for the corresponding particle type properties. Life is how long a particle exists; Number is how many particles are created; Size is how big the particles are; Velocity is how fast the particles travel; Weight controls how fast the particles fall or rise; Spin is the amount of rotation that the particles have; Motion Randomness is how much randomness is applied to the particle motion; Bounce is how much the particles bounce when hitting a deflector.

(Remember that these emitter properties listed above are “scale factors” that are applied to every particle type of the emitter, and the values (y-axis) are percentages. If the corresponding particle type property is set to 0, then it does not matter what the emitter property is set to – the result will be 0. This will become apparent later, but it is an important point.)

The Zoom property is also a scale factor, but there is no particle type Zoom property. So what does it scale? Zoom scales both the particle type size and velocity to give the appearance that the particles are farther or closer to the viewer. Let’s start a new example to demonstrate this.

Start a new project (click New). Now select the "Explosion 3" emitter (from the "Group 2" library folder). Before you add it to the stage, let’s try something new. Every emitter we’ve added so far has been added at frame 1, but that’s not necessary. You can add an emitter to the stage at any frame you want. It will not activate (start emitting particles) until the frame that you added it at.

Jump to frame 10. Now add an emitter toward the left side of the stage. Now jump to frame 30 and add a second emitter of the same type near the center of the stage. Finally, jump to frame 50 and add a third emitter near the right side of the screen. Rewind to frame 1 and start playback. You should se a series of three explosions, time delayed from each other. You should see that the hierarchy window now has three emitters in it, and that each emitter contains five particle types. There is a lot of data in the hierarchy window right now. Just ignore it temporarily, and let’s adjust the zoom settings.


Selecting Objects

We want to select the first emitter we placed on the stage. There are three different ways to select an emitter (when multiple emitters are on the stage). First, we can just click on it on the stage (when in Select mode). (Don’t double-click it or you’ll be jumping ahead to the next tutorial.) This is the most common way of selecting an emitter, but it doesn’t always work. When two or more emitters are right on top of each other, it can be impossible to use the mouse to select the emitter you want. The second method of selecting an emitter is to select the emitter in the hierarchy window. By clicking on the emitter name or any of its properties, the emitter will be selected on the stage. (In the same way you may have noticed that when selecting an emitter via the stage the emitter becomes selected in the hierarchy too.) The third method for selecting an emitter is to use the keyboard shortcut of the Tab key to cycle between emitters. You may also use Shift+Tab to cycle through in the reverse order. Note that these keys only cycle through the emitters that exist on the same layer (layers will be covered later).

It is also possible to select multiple emitters at a time. You can Ctrl+click on each emitter you want to select, you can use Ctrl+A (or on the Edit menu "select all") to select all of the emitters on the current layer, or you can click on no emitter and drag to create a selection box. As the selection box touches the "center point" of an emitter, it becomes selected and will highlight. Once the objects are selected, you can move them using the Move function, delete them, Cut/Copy/Paste them, etc. If you want to move them by dragging them (instead of using the Move function), you must Ctrl+click on one of the selected emitters, release Ctrl (unless you want to move the entire emitter path) then start to drag. If you don't Ctrl+click the emitter and only click it, then it becomes the only emitter selected.

So select the first emitter using any of the three methods you prefer (but don't select multiple emitters, because that doesn't make sense right now). Now select the zoom property in the hierarchy window. Make sure you select the zoom property for the correct emitter. If you don’t then you will see a different emitter selected on the stage.

Now look at the graph window. The zoom graph should show a horizontal line at 64%. Jump to frame 20 and make sure Show Particles is on. Grab the key at frame 1 and drag it down to a value of about 20%. Notice that the entire explosion appears to get smaller, as if it is farther away. Now jump to frame 60 and select the third emitter (the one near the right side of the screen). Change its zoom graph so it is a horizontal line at about 120%. It should appear much larger as if it is closer to the viewer. Now Rewind to frame 1 and Play. You should see the same series of time delayed explosions, but now the first appears to be far away, the second is closer, and the third is right in your face!



You probably noticed that during playback the third explosion “covered up” part of the second one, which added to the illusion that the third blast was “closer” than the second. It’s important to note that emitters are drawn in the order they appear in the hierarchy window. The topmost emitter in the hierarchy is drawn last (on top). When we discuss layers, the same rule will apply – layer on top is drawn last (it’s closer to the viewer). The same goes for the particle types in an emitter – the topmost particle types are added last – although this usually does not make a difference with particle types.

What if we wanted to make the second explosion the “closest”, and the third appear to be further away? First let’s change the zoom of the third emitter so it is 64% again (you can just use Undo). Then change the zoom of the second emitter to 120%. If you press Play you’ll see that it’s just not right – we need to change the order of the second and third emitters so the second emitter draws last (is the topmost emitter in the layer). This is easy.

First, just collapse the hierarchy so it’s easier to look at. (Click on each of the small minus signs.)



In order to change the order of emitters on a layer, you drag and drop them into place in the hierarchy. (This is often referred to as "drag and drop"). When dragging an emitter in the hierarchy (and everywhere else in particleIllusion that drag and drop is possible), the emitter is placed below the emitter it is dropped on. In this example we want the middle emitter to end up on top, so we actually have to drag the topmost emitter down one position. Drag the topmost emitter ("Emitter 3 2") and drop it on the middle emitter ("Emitter 3 1"). The hierarchy should update to this:



Play and the second explosion should now appear to be the closest.

Save this project now: select Save As from the File menu, and save this file as “Tutorial 2”.


Now that we’ve covered Zoom, let’s get back to the rest of the emitter properties in the hierarchy window. Start a new project, then select the "Shoot Smoke" emitter. Place it near the center of the stage. Jump to frame 40 or so and make sure Show Particles is on.

       

The Visibility property controls the overall transparency of the emitter. The visibility of each particle type can also be set, so the emitter visibility is again a scale factor that is applied to each particle type. Change the "Shoot Smoke" emitter's visiblity and see how that affects the particles.

The Tint Strength property determines how much of the emitter tint color is blended into the particle type colors. The default tint color is gray (we’ll see how to change the tint color in the next tutorial) so you can adjust this value and see how the particles get tinted gray. Tinting is usually the easiest way to change the color of an emitter’s particles. Tinting can also be used to help simulate distance – applying a slight blue or gray tint to an emitter may make it appear to be more in the distance (when used in combination with the visibility and zoom properties).

The Emission Angle and Emission Range properties determine the direction in which particles are emitted.

Select the emission range property. The data key is at10 degrees in order to confine the particles to a narrow "stream". (Note that the title of the graph shows the units for the values on the y-axis of angle graphs are degrees instead of percent.) Try increasing the emission range value and see the effect on the emitter.

Set the emission range value back to 10 degrees and select the emission angle property. As you drag the data key up and down, you’ll see the stream of particles sweep around.

Emission range has a graph value range of 0 - 360 (degrees). Emission angle and Angle have graph value ranges of -2000 to +2000. How can an angle value be larger than 360 degrees? Well, it can't really, but the larger values allow you to easily do multiple rotations.

Let’s do a simple animation of the stream of particles completing three complete revolutions in 120 frames. First drag the initial data key down to 0 degrees. Now click on the graph window at frame 120. Drag the new data key up to 720. That's two revolutions (360 x 2 = 720) in 120 frames.

Rewind and Play. You should see the stream of particles create a spiral pattern as the emitter makes two complete revolutions.





You can easliy make the emitter rotate in the opposite direction by moving the data key at frame 120 from 720 to -720, make it rotate slower by making the data key value smaller (500 for example) or moving the key to a different frame (200 for example).

The Active property determines when an emitter is on (creating particles). In the “Tutorial 2” example with the three explosions, we added emitters at frames 10, 30, and 50. Load that project now and look at the active graph for each emitter. The active graph for the second emitter looks like this:



Since the emitter was added at frame 30, the emitter doesn’t go active until frame 30.

The active graph is different from the other graphs in that the first data key is not tied to frame 1. Also, every additional key added causes a toggle between active and inactive (on and off). Back to this in a minute.

If the active graph is used to turn an emitter on and off, why doesn’t the graph above show the point where the emitter turns off? The explosion emitter obviously stops emitting points 15 frames or so after it starts emitting. How can this be? The "Explosion 3" emitter doesn’t stop emitting points by using the active graph – it uses the number graph. Here’s the number graph for that emitter with the active graph as a reference graph:



You can see that after only about 5 frames the number of particles starts decreasing to 0%, and by 10 frames after the start of the explosion there are no more particles being added.

The reason the active graph was not used to stop emitting particles in this case is that when an emitter goes inactive, all of its particles immediately disappear. Since the particles created in the explosion need to linger and fade out, we couldn’t use active to turn the emitter off. There will probably be very few cases where you will want to use the active graph to turn an emitter off.

The final emitter property visible in the hierarchy window is Angle. This property does not usually apply to point emitters, and we haven’t talked about line and elliptical emitters yet, so we’ll come back to this in a later tutorial.


There is one more emitter property that is currently not visible. In order to make it visible, r-click on the emitter size property in the hierarchy and look at the Lock Aspect option:



You can see that Lock Aspect is checked. This indicates that the particle X and Y sizes are "locked", so when you adjust the size property, the particle size increases horizontally and vertically at the same time. If you uncheck Lock Aspect you will see a change in both the hierarchy and the graph window. The hierarchy now has size x and size y properties instead of just a single size property:



The graph window has also changed, and now displays the size x graph instead of the size graph:



The particle X and Y sizes can now be adjusted independently of each other. Changing the size x graph value so it is at about 80% results in particles that are no longer square -- they're stretched.

     

Not the best choice for this explosion emitter, but you'll certainly find a use for this function.


We’ll continue our look at the emitter and particle type properties in the next tutorial.



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