Creating Bulb Fluctuation Using Expressions in After Effects

In this tutorial I'll show you how to make an effect of bulb fluctuation in After Effects using simple expressions. You can then control the fluctuation manually or automatically. 

Preview

Bulb

1. Creating Elements in Photoshop

Step 1

Open Photoshop.

Step 2

Press Ctrl-N to create a new composition. Set the Width and Height of the document as 1280 and 720 respectively.

Step 3

I have a bulb image which I import in the composition. Rename this layer as Bulb.

Step 4

With the Bulb layer selected, press Ctrl-J key to make a duplicate layer of it. 

Step 5

Rename the copied layer as Bulb Glass.

Step 6

Turn off the visibility of Bulb layer. With the help of Eraser tool, erase the bottom part of the bulb in the Bulb Glass layer.

Step 7

Turn on the visibility of the Bulb layer. 

Step 8

Press Shift-Ctrl-N to create a new layer. Rename this layer as Slider.

Step 9

Make a shape of slider in the Slider layer as shown in the following image.

Step 10

Following the same way, create a new layer and rename it as Slider Button. Create a button like shape in this layer as shown in the following image.

Step 11

Press Shift-Ctrl-N to create a new layer. Rename this layer as Filament.

Step 12

With the help of Brush tool, paint the filament with the white color.

Step 13

Save the file as Bulb.PSD.

2. Compositing in After Effects

Step 1

Open After Effects.

Step 2

Press Ctrl-I key to open the Import Files window. Select the saved Bulb.PSD file and click on the Open button.

Step 3

A small option window appears. Select Import Kind as Composition and then click on OK.

Step 4

All elements of the Bulb.PSD layer get imported as Bulb composition. Double click on the Bulb comp in the project window. You get all layers on the timeline.

Step 5

Make an elliptical mask on the Background layer. Increase the feather amount of the mask to make the corners a bit dark. 

Step 6

With the Bulb Glass layer selected, go to Effects > Generate > Fill and apply the effect.

Step 7

Choose a very light yellow color as the fill color. The bulb’s glass adapts the color accordingly.

Step 8

With the Bulb Glass layer selected, go to Effects > Sapphire Lighting > S_Glow and apply the effect. Increase the Glow Width amount to 120 and Brightness amount to 2. 

Step 9

Follow the same process with the Filament layer also. With the Filament layer selected, go to Effects > Sapphire Lighting > S_Glow and apply the effect. Increase the Glow Width amount to 36 and Brightness amount to 5.

Step 10

With the Filament layer selected and Alt key pressed, click on the stop watch of Brightness property. It opens the expression editor. Here write the following code:

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y= thisComp.layer("Slider Button").transform.position[1];

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yMin = 420;

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yMax = 445;

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linear(y,yMin,yMax,5,0)

Step 11

Follow the same procedure for the Opacity value of the Filament layer. With the Alt key pressed, click on the stop watch of Opacity property. It opens the expression editor. Here enter the following code:

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y= thisComp.layer("Slider Button").transform.position[1];

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yMin = 420;

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yMax = 445;

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linear(y,yMin,yMax,100,0)

Step 12

Follow the same procedure for the Opacity value of the Bulb Glass layer. With the Alt key pressed, click on the stop watch of Opacity property. It opens the expression editor. Here enter the following code:

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y= thisComp.layer("Slider Button").transform.position[1];

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yMin = 130;

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yMax = 445;

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linear(y,yMin,yMax,100,0)

Step 13

If you want automatic fluctuation, then with the Alt key pressed, click on the stop watch of Position property of the Slider Button layer. It opens the expression editor. Here enter the following code:

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x = transform.position[0];

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y = transform.position[1];

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w = wiggle(6, 210); 

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[x, w[1]];

Step 14

Move the Y position of the Slider Button layer. The intensity of the filament and the glow of the bulb can be controlled with the movement of the slider button in Y direction. 

Keep playing with the values of the yMin and yMax to get different types of results. 

Conclusion

Although some knowledge of mathematics and scripting is required, though you can do amazing and complex works easily with the help of expressions as it saves your a lot of time. 

Keep watching this space as I will come up with some more tutorials based on expressions.