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Simulating a Tornado in After Effects

COW Library : Mark Simpson : Simulating a Tornado in After Effects
Simulating a Tornado in After Effects


by Mark Simpson,
JAM Digital, Redondo Beach, California, USA
©2001 by Mark Simpson. All rights are reserved.Used at CreativeCow.net by kind permission of the author.

Mark Simpson ARTICLE FOCUS:
Mark Simpson
uses the masking capabilities of After Effects along with some 3rd party plug-ins to simulate an animated Tornado.


This tutorial is in response to the many requests about how to make a Tornado in After Effects. This simple tutorial uses the pen tool to create multiple masks in conjunction with the 'Turbulator' plug-in, to make a quick and dirty Tornado. It can't compete with the advanced particle emitters of a dedicated 3D app, but it is sure to be useful in some instances, where the lack of time or high end 3D tools required for a fully realistic tornado are not available.



This is how it's done:


PART A: Using AE's 'pen' tool to prepare the landscape source images


The first thing I did was to start with a large image of a golf course ( Corbis Image's "CI_Golf_view_CB008039.jpg" from the "Creating Motion Graphics" CD). I sectioned off a portion of the image in which three hills were stacked in front of each other, allowing some valleys for the tornado to move through. I took the original image (after positioning it in the layer/comp, and duplicated it three times, then masked off each image so that the hills became separate objects. I used a slight feathering on the masks to add a bit more realism to the image.



Original Image


1) Create new project and import your source image into the project.

2) Create a new composition, 9 seconds long, name it 'hills/tornado comp' and drag your image into it.

3) Position and scale your image layer so that you have isolated the area you want to be visible in your final movie.



After Importing into AE and positioning in the comp


4) Create three more copies of the image layer, and rename all 4 layers (from top to bottom) 'front hill', 'middle hill', 'back hill', & 'background'.

5) Double click on the 'front layer to open it in the layer window.

6) Use the 'Pen' tool to create a closed mask, which isolates the part of the front hill that will be used when the tornado moves behind it. Feather the mask slightly where the delineating lines are irregular, so that it handles the shrubbery and other irregularities that exist along the mask line. This will create a more believable look when the tornado passes between the hills.

7) Do the same with the 'middle hill' layer, and the 'back hill' layer (See the following pictures).


'front hill', 'middle hill', and 'back hill' Layers,
(as they appear individually in the composition window after creating masks with the 'Pen' tool.)




The three 'hills' after compositing (using 'normal' as the blending mode).


PART B: Using AE's 'pen' tool to prepare the animated tornado shape matte


1) Create a new composition, 9 seconds long, and name it 'tornado matte comp'.

2) Create a layer, solid white in color.

3) Create another layer, solid black in color (it should now be on top of the white layer in the time layout window.

4) Double click on the black layer to open it in it's own window. Using the pen tool, draw a mask in the shape of the tornado as desired. With the timeline window active and the black layer selected. hit Option>F to open the mask feather control in the timeline. Set the mask feather to 20 pixels (horizontal and vertical). With the timeline window active and the black layer selected, hit Option>M to bring up the mask shape control. Option click the word 'mask shape' in the timeline to set a keyframe at 0 seconds.



The tornado mask in it's layer window



The resulting feathered matte

5) Move ahead to 2 seconds, alter the mask shape in the black layer window, with the intent of making the tornado tail dance and the tornado itself simulate natural changes in shape This will automatically generate a new keyframe.

6) Repeat the process at 4 seconds, and at 6 seconds, changing the mask shape to set keyframes at each.

7) Move ahead in the timeline to 7 seconds. Hit option>f to bring up the mask feather control, and set a keyframe (it should still be set to 20 pixels). Move ahead to 9 seconds, and change the feather setting to 40 pixels, creating a keyframe in the process.

8) RAM preview the comp to see the tornado matte dance and evolve. Go back and make any adjustments to the mask shape and timing to achieve a pleasing result.


PART C: Using Evolution 'Turbulator' to create the tornado's whirling cloud look


1) Create a new composition, 9 seconds long, and name it 'tornado effects comp'.

2) Create a new layer, white in color. Drag the 'tornado matte comp' into the timeline, so that it is topmost in the timeline window.

3) In the bottom of the timeline window, click on the words 'Switches/Modes' to toggle the timeline to show modes. With the 'tornado matte comp' on top of the white layer, set the mode to 'Luma'

4) Select the white layer and apply the 'Turbulator' effect to it. Using the settings as shown in the screenshot below, and the time marker at 0 seconds, set keyframes for 'aspect ratio' and 'horizontal speed'.



Initial Turbulator settings

5) Move the time marker ahead to 5 seconds, set the 'aspect ratio' to '-3.00' and the 'horizontal speed' to '-9.00'.

6) Move the time marker ahead to 6 seconds 15 frames, set the 'aspect ratio' to '-2.50' and the 'horizontal speed' to '-11.00'.

7) Move the time marker ahead to 9 seconds, set the 'aspect ratio' to '-1.75' and the 'horizontal speed' to '-13.00'.


PART D: Putting the tornado in motion to move through the hills

Refer to these images when reading the following steps of the tutorial.



Timeline view showing all keyframe positions and layer order



Position #1 Tornado turns around back hill (steps 5 through 9)
Position #2 Tornado turns around middle hill (steps 10 through 13)
Position #3 Tornado turns around front hill (steps 14 through 16)


The objective here is to create the illusion that the tornado is moving through the valleys created by the hills, gradually working it's way from the distant background to the immediate foreground. This is accomplished by making each hill transparent as the tornado moves around it, until the tornado is eventually only shown against the original background image.

1) Reopen the 'hills/tornado comp' and drag the 'tornado effects comp' into it. Reorder the timeline so that the 'hills/tornado comp' is underneath the three hills layers, but in front of the original background image so that it is the fourth of five layers.

2) Position the 'tornado/effects comp' in the upper right portion of the comp window, and scale it so that it appears to be off in the distance behind the farthest hill. Adjust the opacity to taste. Set the time marker to 0 seconds and set a keyframe for position, scale, and opacity.

3) Move ahead in time to 2 seconds. Move the 'tornado/effects comp' towards the horizontal center of the image. Adjust the scale and opacity so that the tornado seems to be somewhat closer, but still behind the farthest hill.

4) Move the time marker ahead to 2:10. Increase the scale slightly and increase the opacity so that the tornado appears to move slightly towards the camera.

5) Move the time marker ahead to 4 seconds. change the position of the 'tornado/effects comp' layer back to the upper right portion of the comp window so that the tornado is sitting to the left of the 'V' formed where the back hill and the middle hill meet. Adjust the 'tornado/effect comp' layers opacity and scale so that the tornado appears to move slightly closer to the camera.

6) Ensure that the opacity of the 'back hill' layer is set to 100% and set a keyframe for that layers opacity.

7) Move ahead in the timeline to 4:10 and set the opacity of the 'back hill' layer to 0% creating a new keyframe in the process.

8) Adjust the position, opacity, and scale of the 'tornado/effects comp' layer so that it appears to move slightly towards the camera and to the right of the 'V' formed where the back and middle hill meet, creating new keyframes in the process..

9) Move the time marker ahead to 5 seconds, and adjust the scale and opacity of the 'tornado/effects comp' layer, so that the tornado appears to move slightly towards the camera, creating new keyframes in the process.

10) Move the time marker ahead to 6 seconds. Adjust the position of the 'tornado/effects comp' layer so that it sits to the left of the 'V' formed where the middle and front hills meet, setting a keyframe in the process.

11) Ensure that the opacity of the 'middle hill' layer is set to 100% and set a keyframe for that layer.

12) Move the time marker ahead to 06:10. Adjust the position, scale, and opacity of the 'tornado/effects comp' layer so that it appear to move slightly toward the camera creating new keyframes in the process.

13) Set the opacity of the 'middle hill' layer to 0%, creating a new keyframe in the process.

14) Move the time marker ahead to 07:00. Adjust the position and scale of the 'tornado/effects comp' layer so that it moves from behind the front hill, to almost entirely off screen to the right and appears to move much closer to the camera, creating new keyframes in the process. Set the opacity of the 'tornado/effects comp' layer to 100%, creating a new keyframe in the process.

15) Ensure that the opacity of the 'front hill' layer is set to 100%, and set a keyframe for that layer.

16) Move the time marker ahead to 07:10. Set the opacity of the 'front hill' layer to 0%, creating a new keyframe in the process.

17) Move the time marker ahead to 08:00. Change the position and scale of the 'tornado/effects comp' layer so that it is centered in the comp and consuming most of the comp window, creating new keyframes in the process.

18) Move the time marker ahead to 09:00, and adjust the position and scale of the 'tornado/effects comp' layer so that it is beginning to move off screen to the left, and consumes almost all of the comp window, creating new keyframes in the process.

19) Apply the following effects to the 'tutorial/effects comp' layer in order and adjust them according to the images below:

FE Vector Blur (Comes free with the book 'Creating Motion Graphics)

Spherize (An After Effects effect) Use my settings as a starting point, but adjust to your project and tastes.

Brightness and contrast (An After Effects effect)

DE RainFall (Part of DigiEffects Delirium set)

CE Radial Shadow (part of Cult Effects Set)



Use these settings as a general guide to start from



Use these settings as a general guide to start from



Use these settings as a general guide to start from


20) Move the time marker back to 07:00 and set keyframes for the following DE RainFall settings (Use values from the image above): Rain Generate, Min Size, Max Size, Min Opacity, and Max Opacity.


21) Move the time marker ahead to 08:00 and set the DE RainFall parameter from above to the following settings:

Rain Generate:75
Min Size:10
Max Size:30
Min Opacity:50
Max Opacity:255

22) Ram Preview the composition, and make any adjustments to taste.

23) Save and Render the project.


Enjoy,
Mark Simpson


Would you like to know more about Mark and see other articles written by him? Click here.

--Evolution will be built into After Effects 5.0 and this tutorial should be easily adaptable for use with AE 5.

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