| One of the most popular types of animations is the particle effect, which is used to create effects such as snow, rain or fireworks. Kwik creates this type of effect with the Multiplier Replacement feature.|
In our storybook app, the storyline calls for snow to slowly stop on page 12. This is a great opportunity to use the Kwik Multiplier Replacement feature. We can start the snow falling when the page first loads and after a few seconds, the snow will stop.
As the name suggests, the Multiplier Replacement feature makes multiple copies of the object that is on a layer and places all the copies on that same layer. You have control over where these copies appear on the layer and, using the built-in physics editor, you can also control the movement of the copies. In our case, we have one snow flake on our layer. For our sample app, we will tell Kwik to make 200 copies of that one snow flake.
We don't want all 200 flakes to appear on the page at the same time. That would give the effect that someone threw a snowball at the screen. We want to create a snowfall effect. So we will set a time interval between each snow flake's appearance on the page. After testing a little, I found the interval of .1 second between snow flakes gave a realistic effect. You may wish to use a different setting here, depending on the effect your wish to create.
Also, we don't want all the snow flakes to appear at the same location on the page. Again we would get a snowball effect instead of a nice snowfall. Have you noticed that snow falls randomly in the real world? Each snow flake seems to appear spontaneously and drifts downward at its own pace. To add reality to our animation, we will tell Kwik to place each snow flake in a random location on the screen.
Not all snow flakes look the same in the real world. Some snow flakes are tiny and difficult to see. Other flakes are large and bright as they reflect the light. Another way that we will add reality to the snowfall animation is to tell Kwik to vary the transparency and scale of the snow flakes.
Once we have the snow flakes on the screen, we need a way to make them move. We can use the Kwik built-in physics engine to create real-world effects such as gravity. We will vary the gravity affect, causing some snow flakes to fall faster than others.
All of these settings work together to create a realistic animation, which is why particle effects are so popular with animators.
Let's create the snowfall.
Go to your LearnKwik folder and make a backup copy of the Template project folder. Rename the backup folder by adding the current date to the end. (TemplateMM-DD-YY).
- Open your project in to Photoshop.
- Select page12 from the list of pages in the Kwik panel. In the Page/Components section of the Kwik panel, you should see "@ page12" at the top of the section.
- Add a new layer above the bottom layer and name it "snow_pg12".
- Open the mockup psd file in to Photoshop and copy the snow flake.
- Paste the snow flake on to the snow_pg12 layer.
- Select the Layers and Replacements icon from the Categories bar.
- Click the Multiplier Replacement tool from the Toolset. This will open the Multiplier Replacement dialog box.
We can create several types of effects from a slow snowfall to a faster, thicker snowfall.
Amount: As you would expect, the more copies of the snow flake that we add to the page, the thicker the snowfall. If we want a light snowfall, we would use a small number of flakes such as 50. To get a thicker snowfall, we will use a much higher number of copies. In the sample app, we will use 200 flakes.
Time Interval: The speed of the snowfall can be controlled by the interval between the appearance of each snow flake. If we use a very short interval such as .1 second, the snow flakes will be added to the page very quickly, giving the appearance of a fast snow fall. If we use a longer interval of 1 second, the flakes will appear to fall slowly.
- In the dialog box, set the number of copies to 200.
- Set the Time Interval between flakes to .1 second.
Distance: As we mentioned above, we will use the random setting to create a realistic snowfall.
- Set the Distance to Random.
- Random Boundaries: Keep the default settings so that the snow fall will be within the page boundaries.
Alpha and Scale: We can vary the Alpha (transparency) and Scale of the flakes which will create a more realistic effect. Let's set the range from 60% to 100% for both. Therefore, as Kwik adds the flakes to the stage, it will vary the size of the flakes from 60% to 100% of the original flake. We will tell Kwik to do the same for the Alpha (transparency) setting.
- Set the minimum Alpha to 60% and the maximum Alpha to 100%.
- Set the minimum X and Y Scale to 60% and the maximum X and Y Scale to 100%.
- Enable Physics: Check this box to engage the built-in physics engine.
- Wind Physics: Set this to 0.
- Weight Physics: Set this to 10/30. This will vary the rate of each snow flake as it falls.
- Click Create.
- Click File - Save to save the changes to the page12 psd file.
- Select the Export Current Page Only icon and click Publish to preview the animation.
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