Autotek autocad raster design 2010 用户手册
By adjusting the polynomial degree, you can increase the accuracy of the
matching points. However, reducing the error can create a higher degree of
warping in the image as it is transformed to match the control points.
Therefore, you should use the lowest possible polynomial degree that will still
give you an acceptable result. Higher polynomial degrees result in smaller
errors at the control points, but more warping at locations away from the
control points.
matching points. However, reducing the error can create a higher degree of
warping in the image as it is transformed to match the control points.
Therefore, you should use the lowest possible polynomial degree that will still
give you an acceptable result. Higher polynomial degrees result in smaller
errors at the control points, but more warping at locations away from the
control points.
The following table lists the maximum polynomial degrees possible for ranges
of control points. For example, if you select 12 control points, the maximum
polynomial degree you can select is 3. When the minimum number of control
points is used for a particular polynomial degree, the reported errors at the
control points will be zero.
of control points. For example, if you select 12 control points, the maximum
polynomial degree you can select is 3. When the minimum number of control
points is used for a particular polynomial degree, the reported errors at the
control points will be zero.
Maximum Polynomial De-
grees
grees
Number of Control Points
1
3-5
2
6-9
3
10-14
4
15-20
5
21-27
ProdNameShort does not limit the number of control points you can use.
The Preview tool allows you to see the extents of the transformed image before
you actually apply the changes. The convex hull of destination points is
displayed in red, while the convex hull of source points is shown in blue.
you actually apply the changes. The convex hull of destination points is
displayed in red, while the convex hull of source points is shown in blue.
Using four points to rubbersheet (e.g., four corners of an image) usually results
in error at these points. In some applications, such as when rubbersheeted
images will be tiled, this error may be unacceptable. To eliminate this error,
you can change the polynomial equation so that a zero error condition results
from the use of four points rather than three points. This change is made in
the system registry. For complete instructions, go to the ProdNameShort
Support website (http://www.autodesk.com/rasterdesign-support) and search on
the term “4 point rubbersheet”.
in error at these points. In some applications, such as when rubbersheeted
images will be tiled, this error may be unacceptable. To eliminate this error,
you can change the polynomial equation so that a zero error condition results
from the use of four points rather than three points. This change is made in
the system registry. For complete instructions, go to the ProdNameShort
Support website (http://www.autodesk.com/rasterdesign-support) and search on
the term “4 point rubbersheet”.
Rubbersheeting an Image | 33