UM:Warper Warper Basics

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Warper Basics

Both Warp 4 and Warp 9 warpers share common features.


A warp is created by selecting and moving one or more control points. These can be manipulated and controlled interactively using the mouse or the GUI controls.



Owners of a Precision Panel can also use it to control the warper tools.

Control Points

Control points are placed around the edges of the source image.




Warp 4 : four warper control points.

Warp 9 : nine warper control points, including the central control point.


Control points change their look when used :



An unselected control point.


A selected control point


A control point with a mouse cursor proximity indication.

Mouse Control



A control point is indicated in red when your mouse cursor is within range.


To select points :


Select one control point :

Click it with the left mouse button

Select multiple control points :

Hold down the SHIFT key while click selecting points with the left mouse button

Hold down left mouse button and drag to warp image

Marquee Select

You can marquee select multiple control points by drag selecting them :



Drag select multiple points using the mouse.

GUI Controls

Once selected, you can manipulate control points via the GUI controls, using the mouse or keyboard to enter value.



The Warp 4 GUI controls


The Warp 4 GUI controls are shown above, and include separate sliders for the X/Y movement of each Warp 4 control point. Four points leading to eight sliders.


The Warp 9 GUI controls are similar but have eighteen sliders corresponding to X/Y for all nine control points.

Warp 9-as-4

You can make the Warp 9 tool warp in a similar mode to Warp 4 by selecting a corner point and dragging whilst holding down the ALT key :


Mouse drag top-right point :



Normal Warp 9 single point drag and warp behaviour.

+ ALT :



Warp 9 warp behaviour with ALT held down.


Note that the warper behaves in a similar way to Warp 4 and as if the mid-points do not exist. The central point stays locked in place however.



The Precision Panel has a 4 Points toggle to enable this mode. In effect, the Warp 9 tool changes to a Warp 4 :




Frame Violation

For frame violation issues, the Precision Panel has mode that lets you modify all left points in X, all right points in X, all top points in X etc.


Use the Left, Top, Right, Bottom buttons to select the row of affected control points
Then move all the selected points in the X or Y  axes using the All Left X or All Left Y, or All Top X, All Top Y etc.




Using Left / All Left X to select and move only one side of the image in the X axis.


Basic Controls




Values :

0 - >100000 (slider)

Default :



The Scale slider lets you scale the image from image center.



You may want to hide warper boundary artifacts in some circumstances and the Scale control can push these outside the visible frame.




Values :

RGB , R , G , B

Default :



You can choose to warp only a single RGB channel or (by default) all three.



This can be useful for cases (e.g. stereoscopic sequences) that have distortion that differs in one or more colour channels.

Reset Selected Points



This button will reset any selected control points.



This also removes any keyframes associated with the control points.

Warp 9 Extended Controls




Values :

Linear , Bicubic

Default :



Linear interpolation is faster but less accurate than Bicubic.

Center Pinning



Pinning the central control point stops it moving when manipulating other control points and so protects the central part of the image.


Use the Pin Radius to hold a proportion of the central image area steady as you move other control points around.


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