Chapter 14, Warping
| Cropping and Filtering the Output | |
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Chapter 14, Warping |
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There are 10 Warping tools that let you distort the shape of your images:
| Tool | Description |
| Crumple | For creating creases, kinks, and wrinkles in an image--see Crumple. |
| Displace | Offsets pixels in an image using pixel values of another image--see Displace. |
| Lens Distort | Rectifies or creates lens distortion--see Lens Distort. |
| Magnify | Enlarges a portion of an image in either the X, Y, or both axes--see Magnify. |
| Mirror | Creates a mirror effect in an image--see Mirror Tool. |
| Pinch | Compresses an image inward or outward--see Pinch Tool. |
| Polar | Changes the pixel definition of an image from Cartesian to the Polar coordinate system or vice versa--see Polar Tool. |
| Ripple | Creates ripple effects in an image--see Ripple Tool. |
| Twirl | Rotates and twists an image--see Twirl Tool. |
| Wave | Creates a wave effect in an image--see Wave Tool |
The Crumple tool lets you create an image appear crumpled like a piece of paper.
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| Original image | Crumpled image |
The Crumple tool has the following parameters:
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| Use: | To: |
| Amplitude | Control the overall strength of the filter. |
| Time Slice | Make modifications to the fractal patterns yielding random results. |
| Octaves | Control the turbulence. Increase the octaves to get more iterations, therefore, a more turbulent crumpling effect. |
The Displace tool lets you use a control image to drive the displacement used to warp the primary input image. There are two ways to displace a primary image: Modulation and Vectors. Both ways can be combined together by specifying the Modulation Image and a Forward Vectors image.
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You can use a single channel to modulate the displacement along a fixed direction. You can define the fixed distance and angle and the displacement increases or decreases by the intensity of the channels (Red, Green, Blue, Alpha or Luma) of the modulation image.
| Use: | To: |
| Distance | Specify the distance of displacement in pixels. |
| Angle | Specify the angle of displacement all pixels in the image will be rotated by in degrees. |
| Channel | Select which channel from the modulation image will be used to displace the image in a fixed direction as specified by the distance and angle. |
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| Input image | Modulation image | Result image: Distance = 50 pixels, Angle = 30 degrees, Channel = Luma |
You can use a forward vector image to define the displacement of the primary input image. Each pixel can be moved in a different direction. The red component of the image represents the X direction of the motion vector and the green component the Y direction. The vectors can be scaled and rotated before applying the result on each input image pixels.
| Use: | To: |
| Scale | Scale all motion vectors of the forward vectors image. |
| Rotation | Apply a rotation to all motion vectors of the forward vectors image. The rotation is expressed in degrees. |
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| Input image | Forward vectors image | Result image: Scale = 100, Rotation = 20 |
Hint: Decreasing the opacity of the Modulation or Forward Vectors image will decrease the distance of the displacement.
The Lens Distort tool lets you create or correct lens distortion that may be present in image sequences.
Barrel distortion is associated with wide angle (or minimal zoom) lenses. It causes the images to appear slightly curved outward like a barrel. You can notice this when you have straight features close to the image's peripheral sides.
The Lens Distort tool has the following parameters:
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| Use: | To: |
| Mode | Select either lens correction or distortion. This affects all other parameters. The other parameters will be considered either in a distortion or in a correction work flow. The distortion transformation is exactly the inverse of the correction, so keeping the same parameters and putting back to back distortion plus rectification will give back the original result, but filtered twice at each transformation resulting in possible degradation in image quality. |
| Magnitude | Set the first parameter (k1) of the lens distortion equation: rd = r + k1 * r^3 + k2 * r^5. |
| Adjustment | Set the second parameter (k2) of the lens distortion equation: rd = r + k1 * r^3 + k2 * r^5. |
| Anamorphism | Characterize anamorphic asymmetry. Note that this has nothing to do with the pixel aspect ratio of the captured image. |
| Center | Set the X and Y coordinates of the center of the distortion. Those parameters are expressed in pixels. The lens center can also be changed by clicking directly in the player. The center manipulator is always active in the player. The look of the manipulator is a cross. The cross can be manipulated by selecting it and moving it. |
| Height | To determine the region where the lens distortion or correction is applied. This parameter is initialized to the composition height. |
| Fit Source | To set the height input to the input height.This parameter is needed to be able to perfectly inverse a lens correction. |
The following are common use cases for lens distortion or correction:
Footage to be used as a background layer has noticeable lens distortion and footage to be composited over the background does not. The Lens distort tool would be added to the dependency graph and used (in Correct mode) to rectify the distortion before compositing the new layer over it. The composite will then be made (any compositing operation) and a second instance of the correcting Lens Distort tool would be added after the compositing operation has taken place using the same values but in Distort mode applying the original distort to both layers.
Applying lens correction on multiple compositions before compositing them together.
Reproduce the lens distortion of one composition on another composition.
Using the tracking data from one composition and applying it to the center of another distorted composition, or composited layers, producing interesting animated effects.
Analysis of radial distortion computes the magnitude and adjustment parameter from a three point spline created in the player to identify distortion. The analysis is only available when the lens mode is set to "Correct". All parameters except the magnitude and adjustment are used to compute the new magnitude and adjustment. The magnitude input will be set at the current frame when the analysis is finished. Note that only one spline can be created at the time. The spline is not animatable.
Set the Mode to Correct.
Draw a three point spline along edge of any distorted features within the image that should be straight. When three points are drawn, the select tool will be activated.
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Modify the existing spline.
Click the Analyze button to analyze radial distortion from the created spline. The image is corrected and the Magnitude and Adjustment fields are updated.
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To remove the spline, click Clear. Note that this removes the editable spline only, but does not remove the correction. If you add a new spline, corrections will be additive.
To begin a new analysis, click the Reset button in the Tools Options.
To correct an analysis, use Undo (Ctrl + Z).
The Lens Distort tool has an Output tab with the following parameters:
| Use: | To: |
| Crop | Change the size of an image--see Cropping and Filtering the Output. |
| Filtering | Smooth the transformed pixels--see Cropping and Filtering the Output. |
The Magnify tool lets you magnify a region of an image.
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| Original image | Image with Magnify |
The Magnify tool has the following parameters:
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| Use: | To: |
| Amount | Control the power of the magnification. Default setting is 1.00000. |
| Direction | Set the direction of the magnification. Setting to Horizontal results in a rectangular magnification region, enlarged in the horizontal direction. It can also be set to Vertical which enlarges the image in the vertical direction. Or it can be set to Both resulting in a circular magnification region, such as a magnifying glass. Default setting is Both. |
This tool mirrors the image along the Y=0 axis. There are no additional controls in this tool beyond the standard warping controls.
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| Original image | Mirror tool applied |
The Pinch tool lets you pinch or squeeze an image either inward or outward from a defined center point.
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| Original image | Positive pinch value | Negative pinch value |
The Pinch tool has the following parameters:
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| Use: | To: |
| Amount | Control the severity of the pinch. Positive pinch pulls the image inside the cone, making it appear to recede. Negative values stretch the image over the cone, moving the center point closer to your point of view. |
The Polar tool lets you transform the input image from Cartesian coordinates to Polar coordinates or vice versa. When using Polar to Cartesian, the effect stretches a round object so that it appears to straighten out. When using Cartesian to Polar, the effect bends an image around its center so that it appears round.
An option menu is used to choose if the transformation is from Cartesian to Polar or Polar to Cartesian.
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| Original image | Cartesian to Polar | Polar to Cartesian |
The Polar to Rectangular tool has the following parameters:
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| Use: | To: |
| Mode | To switch between Polar to Cartesian and Cartesian to Polar (default is Cartesian to Polar). |
| Offset | Rotate the result of the Cartesian to Polar conversion and offset the result of the Polar to Cartesian conversion. The value is expressed as an angle that represent a circular offset in Cartesian To Polar and an horizontal offset Polar to Cartesian mode. |
The Ripple tool lets you create ripple-like effects from the center of the image outward.
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| Pond Ripples | Out from center | Around Center |
The Ripple tool has the following parameters:
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| Use | To |
| Mode | Determine the ripple effect.
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| Use: | To: |
| Amplitude | Scale the amount of warping distortion. Increase for more severe distortion. |
| Frequency | Set the number of waves per frame. |
| Max Ridges | Control the total number of ripples that can be generated. For example, set Max Ridges to 5 to create 5 rings of distortion; the area inside and outside of the rings are unaffected. |
| Spread | Set the distance between the ripples and the center. Animate the spread to create continuous rippling of the image. |
| Damping | Control how the ripple amplitude is decreased over distance.
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The Twirl tool lets you spin, twirl and rotate the image.
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| Original image | Image with Twirl tool applied |
The Twirl tool has the following parameters:
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| Use: | To: |
| Amount | Control the severity of the twirl. Positive twirls the image clockwise. Negative values spin the image counter-clockwise. The twirl angle can also be changed with a rotation manipulator in the player. |
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Twirl the rotation. |
The Wave tool lets you simulate waves in a single direction (as opposed to circular waves as found in Ripple).
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| Original image | Image with Wave tool applied |
The Wave tool has the following parameters.
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| Use: | To: |
| Amplitude | Scale the amount of warping distortion. Increase for more severe distortion. |
| Compression | Warp pixels parallel to the wave direction. |
| Frequency | Set the number of waves per frame. Increase for more waves, decrease for fewer. |
| Phase | Shift the position of the waves along the direction of wave motion. |
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