| 03rd Feb 2006 | Axeman |
In order to assist my fellow users in harnessing the full power and potential of the particle engine in EffectsLab and VisionLab, I have put together this epic tutorial which takes you through all of the particle engine features while creating a realistic fire effect.
In this tutorial, we will cover only the flames which are used in the above clip. I hope to cover the smoke aspects in a future tutorial.
Standard text will explain the various functions of the particle engine.
Red text will be used when we are discussing the physics and other behavioral aspects of real fire. Understanding how real fire moves is crucial to creating a convincing effect.
The toolbox will change to display all the particle engine controls.
Here you have full control over the most defining visual aspect of your particle effect.
Textures are images that are used to draw each individual particle that comes from your emitter. When you add a bare particle effect to your timeline (ie, not a preset), it has no textures applied.
Instead there is a red cross placeholder marking the location of each particle. Once you import some textures, the red crosses will be replaced by the images.
All of the textures you import are shown in a list in the Texture Browser. You can import new textures by clicking the blue folder icon.
Clicking on the white 'i' symbol next to each texture name will display a preview of the texture image. To remove a texture, right-click on its name in the list and select “Delete”. As of version 937, you can have up to 10 textures in each particle effect.
There are several parts to a burning fire. The main part of the fire is very bright, nearly white, and has a fairly constant mass, which moves about a bit. Beyond that, there are the seperate flames that lick up and outward. These are typically not quite as bright, with a bit more orange, red or yellow color to them. In addition to that, there will be sparks and embers that spit up out of the fire, or are carried up by the rising hot air currents.
At the bottom of the Texture Browser area there is a control for how the textures are applied. The options in the menu are Single, Animated, and Animated (random start).
Single means that each particle will use a single texture file throughout its lifetime.
Animated allows you to use animated textures, or sprites, on your particles. This means that for every particle that is generated, its first frame will receive the first texture file, frame 2 will receive the second, and so on, until the end of the list of textures. At this point it will start over at the first texture. In order for this to work well, generally your texture files have to be set up to create a looping animation.
Animated (random start) is similar to the animated setting, except that it does not always start at the first texture on the list. Each particle starts at a random texture in the list, then loops through all of the textures, as mentioned above.
• Using multiple textures can give greater depth and realism to your effect.
• Textures will greatly slow down the rendering time of the canvas. When working on the placement and movement of the particles, you can turn the textures off temporarily by using the Preview Emitters option in the Canvas menu. Once the particles are moving the way you like them, you can turn Preview Emitters off to see how the particles work with the textures again.
This section of controls allows you to adjust the location of the emitter, the source of the particles, and how the particles will react once they have been emitted.
There are two types of emitters available.
Point emitters are, not surprisingly, a single point on the canvas from which the particles spew forth.
Rectangle emitters, as I'm sure you've worked out by now, are rectangular shapes from which the particles are generated. The size and aspect ratio of the rectangle are completely adjustable.
Both types of emitter can be moved about the screen simply by clicking and dragging them to where you want.
IMPORTANT: You cannot change from a point emitter to a rectangular emitter without losing all of the keyframe information which you have set. Be sure to select the appropriate emitter type before you start creating your effect.
Fire needs oxygen to burn, that is why flames would shoot out of our window. As the oxygen in the building is used up, the flames reach up and out to find more.
Immediately below the Emitter Type selector are two read-out windows which will show the location of a point emitter on the canvas. If you are using a rectangle emitter, they will be blank. The first read-out shows the location on the X-axis, measured in pixels, from left to right of the frame. The second window is the location on the Y-axis, measured in pixels, from top to bottom.
The final attribute for the position of the particles controls how they relate to the emitter after they are emitted.
Free From Origin means that once the particle is emitted, it will follow its set trajectory until the end of its lifetime, regardless of how the location of the emitter changes afterward.
Stuck To Origin means that their relationship to the origin point remains constant, so that if the emitter moves, the particles will follow it. If the emitter spins, the particles will spin around the center point of the emitter.
Here we can set how many particles we are dealing with and what direction they will travel, among other things. First off, we set whether there are any particles being created at all.
A very basic control, this one! When the emitter is On, particles will be generated. When it is Off, no particles will be emitted. Turning off the emitter has no effect on the particles which are already in existence.
Controls the maximum number of particles that can be in existence at any given time. If the Particle: Max is 500, then once 500 particles are created, no more particles can be emitted until some of the existing particles reach the end of their lifetime and disappear.
Controls how many new particles are created each frame.
Controls how long (in frames) the particle will last before it disappears. This also has a big impact on many of the other settings, which I will go into below.
Next in the Particle Creation controls we have a menu where we can select the reference point for the angle of our particle emission.
Relative to Canvas means that 'up' is the top edge of the canvas.
Relative to Animation means that as the emitter moves around the screen, the direction that the particles register as 'up' will relate to the direction in which the emitter is moving.
So if you animate your emitter moving from the top left to the bottom right of the screen, with Relative to Animation selected, and the emitter rotation is set to zero, then the particles will emit at an angle toward the top left corner.
• For creating trail effects, such as a missile or comet tail, use the Relative to Animation option. It will cause the emission to always follow your emitter, wherever it moves.
In the middle of the Particle Creation controls, you will see a circle with a small diamond in it. This Direction Wheel is used to set the direction in which the particles will be sent forth.
Simply click on the diamond and drag it in the direction of your preference. For example, if you want the particles to move toward the right side of the screen, drag the diamond to the right hand side of the Direction Wheel. The three readout windows will tell you the angle of your trajectory.
Absolute is the angle in relation to the canvas, in degrees.
Relative is the angle relative to the animation, in degrees.
Turns will tell you how many times you have made a complete rotation, in a percentage.
Once you have the direction set, you can use the Angle Range control to adjust the width of the particle stream. The readout is in degrees to either side of your direction. So if you set the Angle range to 10, you will get a stream of particles 20 degrees wide, centered on the direction you have selected using the circular direction control.
• For emissions that are intended to come toward the camera, use an angle range of 180, to get the particles to emerge in every direction.
The Scale adjusts the overall size of the entire effect. This means that it alters not only the size of the particles, but the relative distance between them, and the size of the overall path that they will follow throughout their lifetime. Later we will work with a control that adjusts only the size of the particles themselves.
At the bottom of the Particle Creation section is a menu with two options.
Draw New Particles Behind means that new particles will appear behind the existing particles. This can often be useful for hiding the actual appearance of the particles, if your emitter is visible.
Draw New Particles In Front means that new particles will appear in front of the existing particles, therefore the actual creation of each particle will be visible.
• Drawing new particles in front can be used to make the emitter point away from you.
• Draw new particles behind can make the effect seem to be coming toward the screen.
Here we can adjust and alter the actual appearance of each particle over the course of its lifetime. This is the meat of the engine.
Each particle has a texture or sprite that is applied to it, as we have already discussed, but we can also set the color, opacity, speed, and size of the particle throughout its lifetime.
The first control deals with the color and the opacity of the particles.
Click on the Color/Opacity bar to open its editing widget. In this window you have two bars. The top bar is a gradient from white to black and the bottom bar is solid red.
The left end of each bar represents the beginning of the particle's lifetime. The right end is when its lifetime ends.
Look below the bottom left corner of the red Color Gradient and you will see a small red handle. This is a control point on the gradient. Click the handle to select it, then click the box labeled Color: to open the Color Picker.
Here you can select any color you want to give your particles. Pick a color, and click OK to close the color picker. You can click anywhere within the red bar to create a new control point. Each control point can be assigned any color you like, and can be placed anywhere on the color bar.
The Location readout at the bottom of the widget will tell you where your current Control Point is, in a percentage of the particle’s lifetime.
The Opacity Gradient works similarly to control the opacity (transparency) of each particle over the course of its life. Above the Opacity Gradient you will see two control points; a white one on the left, and a black one on the right. Clicking on one of them will enable the Opacity Slider at the top of the widget.
The value readout will tell you how opaque you are at the current setting. 0% means that the particles are completely transparent, and 100% means they are completely opaque. Notice that in the opacity gradient, full opacity is represented by white, and full transparency by black.
In each gradient, you can have up to 20 control points.
OPACITY GRADIENT: 3 CONTROL POINTS
1: Value 100%, Location 0%
2: Value 16%, Location 89%
3: Value 4%, Location 100%
COLOR GRADIENT: 4 CONTROL POINTS
Getting the colors close should be enough, if you can’t get them exact.
1: Location 0%, Red 240, Green 164, Blue 104
2: Location 38%, Red 240, Green 124, Blue 18
3: Location 89%, Red 240, Green 94, Blue 2
4: Location 100% Red 255, Green 0, Blue 0
Guess what? The Color Randomizer controls the randomness of the color assigned to the particles. If you want the particles all to be the exact color you assigned them in the Color Gradient, leave this control at 0. For a bit more variety in the color, which can sometimes help add realism to the effect, you can turn up the Randomizer.
• Using a low setting on the Color Randomizer, you can retain the overall color tone of your effect, while still adding a bit of variety for greater realism.
• Color Randomizer settings do not affect the relative changes over time you have set in the Color Gradient. The first control point color will be randomized, and the relative change between its color and that of the second control point will be retained. For example, if you set the Color Gradient to transition from red to light red, and the randomizer assigns a particle a purple color, that particle will transition from purple to light purple.
Basically works the same as the Color Randomizer, but for the opacity. Opacity Randomizer settings do not affect the relative changes over time you have set in the Opacity Gradient. The opacity of the first control point will be randomized, and the relative change between each subsequent control point will be retained.
The Speed Curve intially appears as a straight line. Similar to the gradients for color and opacity, it represents the lifetime of the particle, from left to right.
Click on the curve to open its editing widget. You should be familiar with the control point concept now, so you will notice that this curve basically edits the same way as the color and opacity gradients.
Click anywhere in the curve to create a new Control Point, then drag the Value Gradient slider to set the speed for that point. You can have up to 20 control points in the Speed Curve. The speed Value is in pixels per frame.
A fire of this size uses a lot of oxygen. As it burns the oxygen inside the building, it begins to choke itself, so it grabs at the oxygen outside. As the air outside is heated by the fire, it rises. These processes are what makes the fire reach up and outward so quicky, as opposed to a small campfire, which has plenty of oxygen, and burns at a slower, more lazy pace.
Paired with the Speed Curve you have the Speed Randomizer, which makes the initial particle speed more variable. Each particle will still follow the speed curve, based on its individual starting speed.
Works the same as the Speed Curve but affects the size of the individual particles. Up to 20 Control Points can be set in the Size Curve, to alter the size of an individual particle over the course of its life.
Use the Value Gradient slider to set the size value for each control point. The size value is a percentage of a full-size (512x512 pixel) texture. So at 25% each particle texture will register at 128x128 pixels on your footage.
The Size Randomizer sets the randomness of the particles at the start of their life. Each particle will still grow or shrink according to the relative settings in the speed Curve.
Here you can set how the particles are blended into each other, as well as the underlying layers. Normal means that the colors of your particle effect will not be altered. Add and Screen are designed to be used with effects which create a light source, such as fire, or some magical effects.
Take a look at your newly-kindled fire. :)
You can use Gravity to pull your particles in a given direction after they are emitted. It can be used to pull them downward, and thus simulate actual gravity, or you can set it to pull them sideways, to simulate the effects of wind, for example. Use the Direction Wheel to set the direction toward which gravity should pull.
The Gravity Strength slider adjusts the strength of the gravity’s pull. This will determine how quickly it affects the particles after their emission, and how quickly they move in the direction gravity is pulling them.
When you have a fire near a wall, the fire (and smoke) will, in general, automatically hug the surface of the wall as they rise. Some of the smoke will often wander about, but the majority of it will stay near the wall surface.
The masking system that is built into EffectsLab and VisionLab is ideal for making our fire appear to be coming from inside the window. Due to the perspective on the building in this shot, we will need to mask the left side of the window, and the bottom of the window, across the sill.
We will use two seperate Masks for this procedure. The reason for this is that the flames will have a fairly hard edge across the bottom, where they come up from the sill. But on the side, where there will eventually be smoke coming out as well, they will need a softer edge to blend more with the smoke.
In the Animate controls for the Mask, we can adjust the Feather (softness) of the edge, and the Transparency of the entire mask. These can be animated to change over time using keyframes.
Also, we can change the shape of the mask at any time by simply dragging the control points of the mask around on the Canvas. We won’t need to animate our mask, but it is a very useful feature for other projects.
And there you have it. The flames are all set, the window is masked, and you are ready to render the effect out and see how it looks.
We will now use the grading controls to further enhance our flame effect. Click on the Grade timeline track for your effect to switch the toolbox to the grading tools.
To smooth our flames out a bit, and blend the particles together more realistically, we will use a bit of blur. There are a number of different blur filters to choose from, including Blur: Angle, Blur: Gaussian, Blur: Radial, and Blur: Zoom. In our case, the reason the flames require some blurring is that they are moving. To simulate a motion blur, we will use the Blur: Angle filter.
Every object on the timeline has additional properties you can access by clicking its main title in the track listing. The toolbox will change to show general information about the clip. A few of the settings can be altered.
Now it is time for one final render, and see how your flames look. Of course, they would look better with some smoke. I hope to do a tutorial on smoke eventualy, but in the meantime, you can download the smoke presets I have created and give them a try, or, if you are up to it, feel free to try create your own smoke.
Hopefully at this point, you have a better understanding of how the controls in the particle engine work. So, if you see any aspect of the effect that needs adjusting, or you feel you could improve it in some way, I strongly encourage you to try it.
Get back into the Emitter Attributes and try making some changes. Maybe you want the flames to go a bit faster. Perhaps you want to try a more complicated effect, where the sparks are created and controlled by their own seperate emitter. Perhaps you think they are too bright and want to bring a bit more color into the effect. Maybe you want to introduce some additional textures, or replace some or all of the textures entirely.
By all means, give it a try. Getting in there and seeing what happens when you make changes is the best way to get a feel for the controls. And don’t forget to submit the effects you come up with to the Presets Library on the site, so the rest of us can use them, too.
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