AutoCAD 2008: How to Convert a 2D Polyline to a Spline
AutoCAD 2008 is a program for designing 3D and 2D objects, including buildings, circuit diagrams and other structures that need precise measurements. Splines, one of AutoCAD's tools, are used in the design of some objects. Each spline is a set of points through which a smooth curve is fitted. By contrast, polylines--another design tool--are sets of points that can combine both smooth and straight segments. Since polylines don't have to be smooth and splines do, converting a polyline to a spline may result in a spline whose shape differs from the polyline.
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Instructions
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Open AutoCAD and create a polyline to convert to a spline: Click "Draw," then "Polyline." Click and drag in the main drawing window to define the polyline's first segment. Click and drag again three or four times to define new segments. Press "Enter" to end the polyline-creation mode.
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Begin converting the polyline to a spline: Click anywhere on the polyline to select it. Then, click "Modify," "Object" and "Polyline."
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Select "Spline" from the pop-up menu that appears and press "Enter." Notice that the polyline's straight line segments are now curved.
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Click anywhere on the curve to select it. Notice the object type that appears in the small window: "2D polyline." This text means that the curve is still a polyline object, even though it appears as a spline object. The following steps complete the conversion to a true spline object.
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Click "Modify," "Object," then "Spline." Press "Enter" when the pop-menu appears, then click the curve to select it. Notice that the small window now displays "spline" instead of "polyline."
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Begin converting another polyline to a spline: Repeat step 1 to make a new polyline object. This time, you'll create a spline whose shape is closer to the original polyline.
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Press "Control-C," "Control-V," then click the mouse. This will make a copy of the polyline, which will help you remember the polyline's original shape.
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Complete steps 2 through 5 on one of the polylines, to convert it to a spline. Notice again that the spline curves even though the original polyline doesn't.
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Make the spline more accurately resemble the original polyline by first clicking it to select it. Then, click in the command window at the bottom of the screen.
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Enter "Splinedit," (the spline edit command). Then, enter "R" for "refine."
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Enter "W" to indicate that you want to change the weight (AKA influence) of the spline's control points. Then, enter "N" to navigate to the second point.
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Enter "100" to increase the second point's weight. Notice that the spline's first segment has become nearly straight, which more closely matches the first segment of the original polyline.
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References
- Photo Credit house plan image by Jon Le-Bon from Fotolia.com
