##### Tutorial #4

In the previous tutorial we looked at all of the emitter and particle type properties in the emitter properties dialog. We ended with a note about the Add to Library button, which was visible because we were looking at the properties for a stage emitter (an emitter that is on the stage). There is one other use for the emitter properties dialog, and that is to view and edit library emitters.

# Libraries

As we’ve already discussed, an Illusion library is a collection of emitters. We can think of it as a palette of emitters, since only the emitters in the currently loaded library are available for adding to the stage. We’ve seen that we can edit the emitters after they are added to the stage using the hierarchy window or by opening the properties dialog for the emitter. What if we want to view or edit the properties of a library emitter?

R-click in the library window. The first line of the displayed menu is not a function – it is the name of the library and is always disabled.

We’ll get to loading and saving libraries shortly.

Select the Properties menu item now. (Note that double-clicking on an emitter in the library window has the same effect.)

The emitter properties dialog opens, but there are a few significant differences. First, you’ll notice that the dialog title displays the library name. Second, you’ll notice that the dialog hierarchy window is a little more complex than we saw when we were looking at the props of a stage emitter.

The hierarchy window for a stage emitter displayed only a single emitter. When looking at the properties of a library, all of the folders and emitters in the library are visible. All of the particle types for each of the emitters are also visible (of course) as well, so there is quite a bit of information displayed here.

We won’t talk about any of the properties here, since they are exactly the same for a library emitter as they are for a stage emitter.

We will discuss the new buttons that are available below the hierarchy window though.

The first button is used to create a new folder. The next button (only visible when a folder is selected) deletes the selected folder. Deleting the folder will delete all emitters it contains as well.

The next button is the New Emitter button. If it is clicked when a folder is selected, a default emitter will be created. If clicked when an emitter is selected, a copy of the emitter will be made, and the emitter will be named “Copy of …”. In both cases the emitter is created in the open folder. The next button is the Delete Emitter button and is only visible when an emitter is selected, and when the folder contains more than one emitter (it is not possible to delete the last emitter from a folder).

Next is the New Particle Type button, which you should remember from the previous tutorial. Clicking it when an emitter is selected creates a default particle type, and clicking it when a particle type is selected creates a copy of the particle type. The Delete Particle Type button is last, and is only visible when a particle type is selected and there is more than one particle type in an emitter.

That’s all we’ll say about the properties dialog for library emitters, so close the props dialog by clicking Cancel.

R-click on the library window again. The Load Library function is used to do just that – load a new library. Select it and the standard Windows open dialog appears. A list of all of the IEL (Illusion Emitter Library) files will be displayed. Select a library file and it will be loaded, replacing the library that was previously loaded. (Note that the previous library will be saved before the new library is loaded.)

For organizational reasons and because of memory restrictions it is not a good idea to create one gigantic library that contains all of your emitters. Create separate libraries for different types of emitters, and load them when needed. Once an emitter has been added to the stage, it is completely independent of the library it originated from – we can load a new library without affecting any stage emitters.

The Save Library As… function is used when you want to save a library as a different name. It is a good way to make a backup of your library, which is important to do. You should make backup copies of your libraries (IEL files) frequently. This will prevent the loss of a lot of work if something should happen to a library file.

# Layers

We’ve spent a lot of time covering the properties of emitters. Let’s look at something completely different now – the layers window.

You may be familiar with the concept of layers from using other applications. In Illusion a layer is simply an invisible surface on which emitters are placed. A layer can also contain an image, images, or AVI. Multiple layers can also be used to help the illusion of 3D, but more on that later.

Every Illusion project uses at least one layer. The layers window displays information about each layer in a project. In this example (and every example we’ve done so far) there is only a single layer, it is titled “Layer 0”, and it does not contain a background image.

The background image (remember that each layer can have one) can be either a single image, an image sequence, or an AVI. If a background image is loaded, a small “thumbnail” version of the image is displayed (in place of the gray rectangle) and the image name is displayed under it. Let’s load a background image.

There are two ways to load an image into a layer. The fastest is to double-click the thumbnail image (or gray rectangle) in the layers window. (You may also load an image by R-clicking in the layers window and selecting Background Image.) A standard Open dialog appears. Find an image that you’d like to use as a background image for this layer. Note that the image will not be resized to fit the size of the stage, but if the image is a different size you will have the option of resizing the stage to fit the image. Remember that the stage area indicates the active area, which is the only area in which anything is visible.

Once you have loaded an image, it will be shown in the layers window, as well as on the stage. (We should point out that when a project which contains background images is saved, a reference to the images is saved in the project but the images themselves are not saved as part of the project file.)

Note that the image name is displayed as well. We’ll take a look at what those icons mean now, but first we need to add an emitter to the stage.

Add a Simple Explosion emitter to the stage. Turn on SHOW PARTICLES. Jump to frame 10. You should see the explosion drawn on top of the image. The background image for a layer is always drawn first, then emitters are drawn.

The first icon (“T”) is the transparency icon. Notice that it has a red slash through it. The layer icons are Off when they have a red slash through them. We’ll come back to the transparency icon.

The second icon (which looks like two small circles) is the “show stage objects” icon. When On the emitters will be shown on the stage. Click the show stage objects icon and see what happens to the emitter on the stage. The emitter symbol is no longer visible on the stage, although the particles are still being drawn. Note that when stage objects are not visible, they can’t be clicked on in the stage window. Turn stage objects back on.

The third icon (looks like a star) is the Show Particles button for this layer. If the Show Particles toolbar button is pressed, this icon (in the layers window) is used to turn off particles for a specific layer.

The last icon (“bg”) is the Show Background Image button. Click it to turn off display of the background image. Note that the image stays loaded, but it is no longer drawn. (“bg” is an abbreviation for “background” that we’ll use quite often.)

If you want to remove an image from a layer (not just make it non-visible), double-click the thumbnail again, or R-click and select Background image from the menu. This function is a toggle – when no image is loaded it loads one, and when an image is loaded it unloads it.

Now back to the transparency icon. Typically you’ll only use transparency in an image when you want something that is under it (on another layer) to show through, so let’s create a second layer. There are two ways to create a new layer: either double click below the last layer, or R-click in the layers window and select New Layer. Either method you use will display a dialog to allow you to change the name of the layer. In this example just type “Top” as the name of the layer. Notice that the new layer was created on top of the old layer. Just as with emitters on a layer, the topmost layer is drawn last.

Remove the bg image from the lower layer (double-click its thumbnail image) and load it for the Top layer (double-click the gray rectangle).

Notice on the stage that the explosion emitter is no longer visible. It is on the bottom layer, and the bg image of the top layer is covering it.

Here’s the layers window after making these changes:

One last thing before we adjust transparency – select the explosion emitter and increase its zoom value to about 100%.

Now click on the transparency icon (the “T” icon) for the Top layer. You may not notice any change because we have not yet determined what to make transparent in the image.

To do that, we can either double-click the transparency icon or R-click and select Transparency from the menu. After doing this, the Image Transparency dialog opens:

In this example we see the image (resized to fit if needed), three empty checkboxes in the Transparent color selection section, and a disabled checkbox that reads “Use existing image transparency”. This last checkbox refers to the image alpha channel information. Since the image we used here does not contain an alpha channel, this option is not enabled. If the image did have an alpha channel, checking this box would use it.

The Transparent color selection area indicates that no transparent color is selected. To select one, check one of the three boxes. Doing that will display a color window and a slider.

The color window indicates the color that will be made transparent in the image. The slider is used to increase the “range” of similar colors that will also be made transparent. Moving the slider to the right increases this range.

To change the color that is transparent, click on the color window. The mouse cursor will change to an eyedropper. Now click the image in an area that contains the color you want to be transparent. After clicking the image, the color window will change to the selected color and the image will update – transparent areas will display a checkerboard pattern.

In this example we’ve made the gray area around the three shapes transparent and closed the dialog. If we make sure that transparency is turned on for this layer (no red slash through the transparency icon) the stage should now show the explosion “behind” the three shapes:

Note that there is no limit to the number of layers that a project can have, although you will rarely need to use more than two or three.

Suppose now we wanted the explosion to appear to be in front of the image instead of behind it. We can easily change the order of the layers to accomplish this.

R-click the layer that we want to move to the front:

The menu items we’re interested in are Move Up and Move Down. These functions work exactly as they did in the hierarchy window when we changed the order of emitters.

Since the layer we selected is already on the bottom it can’t be moved down, so the Move Down item is disabled.

Select Move Up. The layers window will show the change, and the stage will too – the explosion will now be in front.

Notice that depending on which layer is selected (highlighted in light red in the layers window), the emitter symbol on the stage may not be visible. This is to help keep things organized, and to assist us in remembering which emitters are on the same layer.

This function is controlled by the Current Objects Only menu item (see the menu shown above). When checked, only the stage objects (emitters, deflectors, blockers) that are on the selected layer are displayed on the stage. When unchecked, all stage objects are displayed at all times. In this case, selecting an emitter or other stage object that is on a different layer will make that layer selected. (Remember that only visible stage objects can be selected with the mouse.)

The Current Particles Only menu item is similar, but instead of controlling the display of stage objects, it controls the display of particles on the stage. If you have the toolbar SHOW PARTICLES button On, then checking this menu item will only display the particles that exist on the selected layer.

The Current Bg Only option is similar as well, but applies to the background image for each layer.

The last menu item is All Objects on Top. When checked (as is the default) all stage objects are drawn last so they appear on top, regardless of any other layers that may be drawn on top of them. In our example above when the explosion was on the lower layer, the explosion emitter symbol was still visible. If the All Objects on Top option is unchecked, then the bg image of the top layer would have been drawn over the emitter symbol. With this option turned off, it is possible to see how emitters are layered in the project, but for the most part you’ll probably want to leave this option checked.

The only thing we haven’t discussed about layers is how to delete one, and that is simple. R-click on the layer you want to delete, then select Delete Layer.

You’ll need to confirm the deletion, since (as the dialog states) it can’t be undone. Note that when a layer is deleted all emitters on it will be deleted too.

So we now know how to change the order of layers, and previously we learned how to change the order of emitters on a layer, but what if we want to move an emitter from one layer to another?

# Cut, Copy, & Paste

The Cut, Copy, & Paste commands are probably familiar to you from other applications. Typically in those applications Cut removes the selected object and places it either on the Windows clipboard or an application clipboard. If it uses the Windows clipboard, it can then be pasted into other applications. Copy puts a copy of the selected object on the clipboard, and Paste places a copy from the clipboard into the application.

In Illusion Cut, Copy and Paste work on the selected emitter, deflector, or blocker (we’ll get to deflectors and blockers very soon). The selected object is placed on the Illusion clipboard, so it is not available to other applications. The Cut, Copy, & Paste functions are available from the Edit menu, using the standard Windows keyboard shortcuts (Ctrl+X to Cut, Ctrl+C to Copy, and Ctrl+V to Paste), or from the main toolbar:

To move an emitter from one layer to another, simply select the emitter, use Cut to remove it from the project, select the layer you want to move it to and use Paste. Note that the emitter is pasted in exactly the same position. This isn’t a problem when Cutting the emitter, but what do you do when you’re making a Copy of an emitter?

Let’s start a new example. Start a NEW project. Place a Simple Explosion emitter on the stage. Now use Copy to place a copy of the emitter on the clipboard without removing the emitter from the stage. (You’ll notice that the Paste command is disabled until something is on the Illusion clipboard.) Now use Paste to add a copy of the emitter. We can see in the hierarchy window that two emitters are present, but we can only see one on the stage. That’s because the copy was Pasted in exactly the same position as the original.

What if we want to move the new emitter? We can’t click on it and drag it, because clicking selects the first emitter. This is when the MOVE function that we discussed so long ago is most useful. After Pasting the emitter, it will be selected already. Just use MOVE (via the main toolbar button or by pressing “M”) to move the new emitter where you want it. (Note that if the current frame is not 1, an emitter motion path will appear when you MOVE the emitter. You might think that this will result in the emitter moving across the stage and it will, but the emitter will not yet be active, so it will not be visible during playback.)

When you Paste an emitter, its animated properties (any property that changes over time) are adjusted to be relative to the frame number at which it was pasted. This doesn’t make any difference when just making a copy of an emitter or when moving it to another layer. It does make a difference when the current frame number is changed between the Copy (or Cut) and Paste operations though.

Here’s a simple example. Suppose we added an emitter to the stage at frame 30, then spent a lot of time changing properties until it looked the way we wanted it to. Then we realized that we really wanted the emitter to start at frame 35 instead of 30. Adjusting the frame numbers of each of the data keys in each of the property graphs would take forever! Luckily there is a much easier way. Just Cut the emitter, change the current frame to 35, then Paste the emitter. The position of the emitter will be exactly the same, and all of the animated properties will be too, except all of the data keys will be shifted by five frames.

If instead of Cutting the emitter we Copied it, we could add duplicates of the emitter at different frame numbers. Take this example: we have an explosion that we’ve modified (so we can’t just add more copies of it from the library) but we want several of these explosions to occur shortly after one another. We would just Copy the emitter, adjust the current frame, then Paste a copy of the emitter. We could then MOVE it a little if wanted, or just change the frame number and Paste additional copies.

Okay, so now we know that we can use Cut to remove an emitter from the stage, but that places a copy of the emitter on the clipboard (which replaces the previous clipboard contents). Isn’t there a way to just delete an emitter without using the clipboard?

There are two ways to delete an emitter (or other stage object) without using the clipboard. The first you have seen already – R-click in the hierarchy window on the emitter and select Delete from the menu. The other way to delete an emitter is to use the DEL key. Pressing DEL will delete the current emitter, unless a point is selected. What does that mean?

# Emitter Shapes

For the most part the emitters that we’ve been looking at have been “point” emitters. Point emitters emit particles from a single point. There are two other basic shapes for emitters: “line” and “ellipse”.

You may remember this from our discussion of the properties dialog – line and ellipse emitters create particles all along their length instead of at a single point. (You can also set the particles to emit from discrete points along the emitter – remember?) Library emitters can be line or ellipse emitters and will be displayed that way in the preview window. It is also possible to convert an emitter on the stage from one shape to another. For instance, we’ve already changed a point emitter into a line emitter in a previous tutorial. We’ll cover this shortly.

If we select a library emitter that is a point emitter, adding the emitter to the stage requires just a single click of the mouse. To add a line emitter to the stage requires at least two clicks (one for each end of the line), but since a line emitter can contain any number of line segments it can require more. Each click of the mouse defines one of the points of the line emitter. Select one of the line emitters from the library (Sparkle Twirl is one) and add it to the stage. Add three points, then R-click to cancel adding of the last point. We can stop adding points by double-clicking too, but the difference is the last point is not deleted as it is when R-clicking.

When we stop adding points, we end up with an emitter that looks something like this:

The three points that we added are the line points. The small point above the middle line point is the emitter reference point. Think of this as the “center” of the emitter. We’ll come back to it in a moment.

Notice that the last emitter point is highlighted. This is what we meant earlier about the DEL key deleting the emitter “unless a point is selected”. The highlighted line point is selected, so pressing DEL will delete the point instead of the entire emitter. We’ll discuss the line points now.

If we look at the hierarchy window we’ll notice that there is a new addition to the hierarchy: the points folder.

The points folder holds each of the line points for this emitter. The points are simply designated by number. Clicking on one of the points in the hierarchy window selects that point on the stage. You can also select points by clicking on them on the stage, or by using the keyboard shortcut of TAB to select the next point in the emitter. Shift+TAB selects the previous point. (Remember that if no points are selected TAB is used to select the next emitter.) We can deselect all points by either selecting a different emitter on the stage or hierarchy window, or by clicking on the line emitter reference point.

If we select one of the points in the hierarchy window, the graph window will display the Point Position graph for the selected point. This is similar to the position graph for an emitter, but it applies to position changes that the selected point alone makes. There should be just a single position key shown at frame 1 in our example. Before we go any further, select the emitter angle property in the hierarchy window, R-click the graph and select Reset (so we don’t confuse ourselves with too much happening at once). Now jump to frame 30 and drag the middle line point up above the emitter reference point. Notice that the point position graph has changed.

A position key has been added to the graph for this point, which means that this point will change position between frames 1 and 30.

Note that unlike emitter position which can change in either a linear or curved path, point position can only change linearly – it is not possible to make a point move in a curved path.

The MOVE function will also work on the selected line point, and a position key will be created if needed. (See the section on using MOVE with emitters.)

What if we decide that we want to add a point to a line emitter? R-click on the line point that we want to add the point after, then select Add Point from the menu. A point will be added; R-click to abort the addition of the point and L-click to accept it. We can use this function to convert a point emitter into a line emitter too. Note that any points that are added to an emitter will exist from frame 1.

There is something interesting to note about line emitters. Illusion attempts to adjust the number of particles the emitter creates based on the length of the line emitter. The result is that short line emitters will emit fewer particles than long ones. In fact, if the line emitter is made very short – almost a point emitter – it is possible that no particles will be emitted. Likewise very long line emitters may emit too many particles. Therefore, adjustments to the emitter number property may need to be made.

The last emitter shape (beside line and point) is “ellipse”, which includes circles and ovals. When adding an ellipse emitter from the library, the first mouse click on the stage determines the center point of the circle, and the next determines its radius. When an ellipse emitter is added to the stage it can be elliptical (oval shaped) or circular – circular is the default.

The dotted line indicates the radius at which the particles will emit from. The small point at the right edge of the emitter is the “radius handle”. To change the radius of the emitter we can click on the radius handle – we don’t need to drag. The mouse cursor changes to a crosshair, and moving the mouse changes the radius. L-click to make the radius change, R-click to abort the change.

We notice that as we change the radius, the graph window displays the radius graph and the changes we are making. (The Radius property in the hierarchy window is only present when the emitter is an ellipse emitter.) We can also change the radius of the emitter by changing the radius property graph directly.

To convert the circular emitter to elliptical (oval), ALT-click on the radius handle. A second radius handle will appear at the bottom of the emitter. Each of the two radius handles moves independently, so the emitter can be made elliptical. Notice that the hierarchy window no longer has a Radius property, but shows X Radius and Y Radius instead.

To convert the elliptical emitter back to circular, ALT-click on either of the radius handles. The resulting circular emitter will have the radius of the handle on which you ALT-clicked.

(Note that in the same way that the number of particles that a line emitter creates is based in part on the length of the line, the number of particles that an ellipse emitter creates is based on the size of the ellipse. Small ellipses may emit too few particles, and large ellipses may emit too many. Use the emitter number property to compensate.)

As we stated at the start of this section, it is possible to convert stage emitters from one shape to another. To convert a point emitter to a line emitter, R-click on the emitter and select Add Point. To convert either a point emitter or a line emitter to an ellipse emitter, R-click on it and select Make Ellipse. To convert either a line emitter or an ellipse emitter to a point emitter, R-click on it and select Make Point. To convert an ellipse emitter to a line emitter, first convert it to a point emitter, then add a point to make it a line emitter.

We briefly looked at the emitter Angle property in an earlier tutorial, but didn’t go into it since point emitters aren’t really affected by the angle property (unless the Attach to Emitter option is used). Angle makes more sense when applied to line and ellipse emitters. Clear the stage (use NEW) and add an Super Colorful emitter to the stage. R-click and make it an ellipse emitter. Now ALT-click on the radius handle to display both handles and drag one of them so the ellipse is no longer circular. Now if we adjust the angle property value (in the graph window) we can see the emitter rotate on the stage.

That’s all there is to say about line and ellipse emitters. Let’s move on to the other stage objects that we’ve mentioned in passing a few times.

# Deflectors and Blockers

Illusion is all about creating the appearance of 3D in a 2D project – deflectors and blockers can be used to enhance this illusion.

Suppose we wanted to use our Heavy Fire Sparkles emitter to simulate molten metal pouring onto the floor. The molten metal part isn’t too hard – it may take a little tweaking of the emitter – but how do we get the effect of the liquid hitting the floor? We use the only thing that can stop a particle in Illusion: a deflector.

Start a NEW project. Add a Heavy Fire Sparkles emitter in the upper half of the stage, near the center. Now we’ll add a deflector. Select the ADD DEFLECTOR button on the main toolbar:

Adding a deflector is the same as adding a line emitter – deflectors always contain at least two points, but can contain as many as you like.

Click near the lower left corner of the stage. It should look like you’re adding a line emitter, except that the object you’re adding is red instead of white. Click a second time near the lower right corner of the stage, then R-click to stop adding points.

Notice the hierarchy window – it now displays the deflector as well as the emitter.

We can see that deflectors have only a few properties – these properties are the same as the emitter properties of the same name.

If we now REWIND and PLAY, we’ll see the particles fall until they hit the deflector.

The amount of bounce is determined by the bounce property of the particle types, the bounce property of the emitter, and the bounce property of the deflector. How do we set the deflector bounce property? In the deflector properties dialog.

We open the properties dialog for the deflector the same way we open the properties dialog for an emitter: double-click it on the stage, R-click on stage or hierarchy window and select Properties from the menu, or ALT-Enter when it is selected. Open the deflector props dialog now.

The deflector props dialog is not nearly as complex as the emitter props dialog. Here we can rename the deflector, and make it visible during playback by checking the Visible option.

The Bounce slider determines the amount of bounce that the deflector provides to the collision with particles. The slider ranges from 0% at the far left to 200% at the far right. With the slider set to the center – 100% the default position – the deflector does not change the bounce of the particles.

The Hits slider determines how likely a particle will be to collide with the deflector. With the slider set far left, most particles will pass through the deflector. At the far right position (the default) all particles will collide with the deflector.

The Thickness slider is used to increase the collision area of the deflector. When the slider is at the far left the deflector is a line and all particles that hit the deflector will collide with that line. When the slider is moved to the right, the deflector becomes a “rectangle” of increasing thickness, and particles that hit the deflector will hit at various points in the rectangle. This can be used to give the appearance of particles hitting at different points on a surface for example.

Increase the thickness a little, then close the dialog by clicking OK.

We can see that the deflector now appears as a rectangle. REWIND and PLAY, and we will see the particles hitting various places in the deflector instead of along a single line.

Deflectors (and blockers) can be manipulated just as emitters can. A deflector can change position over time just as emitters can, the points of a deflector can change position just as the points of a line emitter can, TAB moves between different deflectors on the stage, you can Cut & Paste a deflector, etc.

Note that particles will only collide with deflectors that are on the same layer as the emitter that created the particles. If you have emitters on different layers that need to collide with the same deflector, use Copy and Paste to put a duplicate of the deflector on the other layer.

We’ve seen now that deflectors are objects that particles can collide with. What are blockers?

Blockers are objects that obscure particles – they block out any particles that go behind them. Using our current example (with the Heavy Fire Sparkles and a deflector) let’s add a blocker. Click the Add Blocker button on the main toolbar:

Since a blocker defines an area of the stage, it requires the addition of at least three points on the stage. Add a blocker to the stage somewhere between the emitter and deflector.

We can see that the particles that enter the blocker area are not visible, as if they are behind the blocker. Although this doesn’t seem to be too useful in this example, it can be very useful when using a background image, since a blocker will copy the portion of the bg image it covers.

If you want particles to appear to go behind portions of an image, a blocker is often the only way to accomplish this.

For example, here’s our molten metal project that we’ve modified to make the liquid appear to fall into a bucket. First we loaded our bucket image, then we created a blocker around the front part of the bucket. The particles now appear to pass between the front and back sides of the bucket.

Note that adding deflectors and blockers to a project may decrease performance, especially when using hardware accelerated OpenGL.

# Preferences

We’ve mentioned hardware accelerated OpenGL (HW OpenGL) a few times in previous tutorials. The biggest concern when using HW OpenGL is the amount of texture RAM that the video card has available. Once the texture memory requirements of the project exceed the memory of the video card, problems may occur. Options to decrease the amount of texture memory that a project uses are found on the HW OpenGL page of the Preferences dialog.

Open the preferences dialog by selecting Preferences from the View menu.

The General page displays the default frame rate used when a new project is created.

Recently Used Files refers to the number of files listed by name on the File menu.

Undo History is the number of actions that it is possible to Undo and Redo.

Background color allows you to set the default background color for a new project. To open the Illusion color picker and change the color, click the color window.

The Show Particle Accuracy slider needs a little explanation. Whenever the Show Particles option is enabled to display particles on the stage and the stage needs to be redrawn, the emitters and particles need to be recalculated. Depending on the number of particles, the frame number, and the speed of the computer, this can take some time.

This recalculation delay can be decreased using the Show Particles Accuracy slider. The default setting of Most accuracy (slider far right) results in the particles being displayed as they will be during playback but takes the most time. By moving the slider toward the left, the particles will be recalculated faster, but they will not look completely accurate. Set the slider far left (least accurate) for the least delay, but the most inaccurate particles.

The HW OpenGL page of the preferences dialog is only visible when 3D hardware with OpenGL drivers is detected by Illusion.

The Use HW OpenGL option will be checked by default. Most likely you will never want to uncheck this option, because that will put Illusion into software (SW) OpenGL mode. SW OpenGL mode is much slower than HW mode, but it will always work, and can be used if the OpenGL driver for your video card has problems.

If you do change this option, the change will not take effect until Illusion is restarted.

The Use Safe Blending option (at the bottom) should only be used if your video card has problems with the normal blending modes. At this time only video cards based on the Permedia 2 chipset require the use of this option.

The Background Images options are used to reduce the amount of texture RAM that a project uses, but only if the project uses bg images. If the project contains no bg images, then these options will not reduce the amount of texture RAM used by the project.

The “Don’t use texture RAM for bg images” option will free the most texture RAM since the bg images will not use texture RAM, but will most likely result in a significant performance decrease.

The “Use half-res version of bg images” option will only require 1/4 of the amount of texture RAM, and will not result in any performance decrease. The bg image will appear more pixelated when this option is used.

The “Use grayscale version of bg images” option will only require 1/2 of the amount of texture RAM and will not result in any performance decrease. (This option can be combined with the “Use half-res…” option to require only 1/8 of the amount of texture RAM with no performance decrease.)

# Loose Ends

There are just a few small things that we need to cover, and your walk through Illusion will be complete.

It is possible to zoom the stage window – you can zoom in to get a closer look at something or to select a stage object, and you can zoom out. To zoom the stage window, R-click on the stage, but not on anything.

Select the Zoom item and the mouse cursor will change to a magnifying glass. Hold the left mouse button and move left and right to change the zoom factor. The zoom factor will be displayed as it changes.

Select Zoom 100% to reset the zoom factor to full size.

While zoomed in, you may need to move the stage (in relation to the stage window) in order to see stage objects that may be out of the window’s frame. R-click on the stage and use the Scroll function to do this. The mouse cursor will change to a hand, then L-click and drag to move the stage.

Select Scroll Recenter to move the stage back to its default position centered in the stage window.

Earlier we learned that we could change the background color from the project settings dialog. It is also possible to change the bg color by R-clicking on the stage and selecting Background Color to display the Illusion color picker dialog.

It is important to realize that Illusion is truly WYSIWYG (“what you see is what you get”) because the stage window is used for all output, even when saving output. For this reason, the dimensions of the output must fit in the stage window because only the stage window area will be saved. This means that in order to work on a project with a 640x480 stage, when saving output the stage window will need to be made at least 640x480 in size – either by making the other windows smaller, or by switching to a higher resolution desktop.

The stage zoom settings are also taken into account when saving output. For instance, if the stage is zoomed out to 50% in order to fit the entire stage in the window and you create an AVI, the AVI will be made of what appears in the stage window: the zoomed out stage. You can make a final adjustment to this zoom factor when saving output in the Output Options dialog.

The Output Size area at the bottom of the dialog shows the current stage zoom factor, and the resulting output frame size.

In this example, the stage zoom was 50% for a 320x240 stage, which results in an output frame size of 160x120. Any image or AVI that is created will be 160x120 instead of 320x240.

Change this zoom factor will show the updated frame size, but notice that the frame size cannot be made larger than the stage window. If while changing the zoom factor the frame dimensions stop changing or are not what you expect them to be, the stage window is limiting the size of the output, and will need to be made larger.

While we are discussing the output options again, let’s look at the other options. The Compressed Image Quality slider is used only when saving JPG and CMP images, so will only be enabled when saving files of those types. Note that a Higher quality setting results in a larger file size (less compression).

The Generate Alpha-Channel option will only be enabled when saving image file formats that support 32bpp images: TGA and BMP. Checking the Generate Alpha-Channel option enables the “shrink” slider.

You’ll note earlier that when particles that are “intense” are drawn on light backgrounds, they tend to blend toward white and lose their contrast. We made the comment that it is usually best to render “intense” particles on a black background. If you do this then want to composite the particle images with a lighter background color or image, the edges of the particles may appear to be darker than you want since they faded into the black background when they were rendered.

The shrink slider is used to shrink the alpha channel for each particle, which can be used to reduce the dark “halo” that is seen around these particles. At the default setting of 0%, the alpha channel is not shrunk. At the maximum setting of 20%, the alpha channel will be made 20% smaller.

Note that the alpha channel is created for the particles in a project only. The background image alpha channel (if it exists) is not taken into account.

# Import and Export

The last topic we’ll discuss is how to move stage object (emitter, deflector, and blocker) position data between Illusion and other applications such as Adobe After Effects.

If we R-click on an emitter in the hierarchy window, we’ll see two options: Import and Export. Select Import and then Position Data (the only option available at this time).

Illusion can use data in two different formats: from Adobe After Effects via the clipboard, or from a simple text file.

The data included in either format is the frame number and x-y position of the emitter at the frame. A position key (linear, not curved) will be created for each line of data. The position information is relative to the upper left corner of the stage, so a position of 0,0 is the upper left corner of the stage. A position of while 50,50 is 50 pixels to the right and down of the upper left corner of the stage.

Remember that an emitter in Illusion must have a position key at the first frame (frame 1). If the data that is being imported has the first position key at frame 1, the data is used as-is. If the data being imported has the first position key at frame 0 instead, all of the frame numbers in the data will be adjusted by one frame so the data will start at frame 1. If the data being imported has the first position key at any other frame number (other than 0 or 1) then a position key will be added at frame 1. The position data from the first key in the imported data will be duplicated.

In the text file format, the data must consist of lines of three numbers separated by TAB characters. The first number is the frame number, the second is the x-coordinate of the position key, and the third number is the y-coordinate of the position key. The numbers can be in floating point or integer format, but each number must be less than 20 characters long. Scientific notation is not allowed. The decimal portion of floating point numbers is truncated. There must be no other lines of text in the file.

For example:

1 20 15

30 100.4 130.6

This would produce two position keys for the emitter. The first at frame 1 at position 20,15 and the second at frame 30 at position 100,130.

The “After Effects 4.0 (from clipboard)” is provided to allow easy transfer of position data from Adobe After Effects to an Illusion emitter. In After Effects, select all of the position keys for the layer by clicking on the position text in the timeline window. Then Copy to the Windows clipboard using CTRL+C. In Illusion select Import Position Data and choose the “After Effects…” option. The position data keys will be created from the data that is on the Windows clipboard. (Note: If the motion in After Effects is curved, you’ll need to create a key at every frame before copying the data to the clipboard. There is a simple After Effects script file “keyall.mm” in the Illusion folder that you can run on the After Effects layer to do this.)

Export of emitter position data is very similar to import, but instead of getting the position data from After Effects or a text file, the emitter position data is saved to the clipboard (for use in After Effects) or written to a text file.

To get the data from the clipboard (after using the “After Effects 4.0 (to clipboard)” option) into After Effects, first select the layer you want to apply the data to in After Effects. Then make sure the marker on the timeline is placed where you want the motion to start then Paste using CTRL+V.

# Closing Words

Although Illusion can be very simple to use (select an emitter and place it on the stage), we’ve seen that there is also a lot of power beneath that simplicity. This power allows you to create an almost endless variety of effects with Illusion. We encourage you to experiment. Modify existing emitters – see how they do what they do. Change particle shapes. Change colors. Get creative, have fun, and when you have something that you’re excited about – share it with others!

Remember there are very few rules when creating emitters in Illusion. We do have one closing word of advice though: “the fewer the better”. You may have a tendency to use a large number of particles when creating a new emitter. You may be thinking that “in order to make this billowing cloud of smoke I need a zillion particles” but this is not the best way to start. In most cases it is not the number of particles that creates the effect you want, but the correct choice of particle shape and size. If you want billowing smoke, use a particle shape that looks like a puff of smoke, make it big enough to see, and use as few of them as possible. (The Simple Explosion library emitter needs less than 100 particles to do its magic!)

Keep an eye on the Impulse web site for new emitters, tutorials, sample projects, and emitter libraries. http://www.coolfun.com

Now stop reading and start playing – create some magic with Illusion!