Contours > Subdivide/Extend Contours (selectable after Contours > Detect Contours) is the creation and modification of contour patches around all yellow (extendable) contour lines, but not around orange (unextendable) contour lines.
Selected Contours group - controls the set of orange and yellow contour lines that are selected for further operations.
Select All button -
When the Operation is Subdivision, this selects all yellow and orange contour lines on the object for the purpose of performing a subdivision. If necessary, remove individual contour lines from the overall selection by Ctrl-Clicking them.
When the Operation is Extension, this selects all yellow contours lines AND converts all orange contours lines to yellow for the purpose of performing an extension. To change a yellow contour line back to orange (unextendable), Ctrl-Click it. To change an orange contour line to yellow (extendable), Click it.
When the Extension Operation is complete, this selects all contours (extended and non-extended) in preparation for a change to the Factor. If necessary, add and remove individual Contour lines to the overall selection by Clicking and Ctrl-Clicking them.
Clear All button - de-selects all contour lines that are currently selected. If necessary, add individual contour lines to the overall selection by Clicking them.
Operations group - specifies the mode of operation of this function -- whether Contour lines are being extended, or extended Contour lines are being modified.
Subdivision radio button - In this mode, the number of contour patches per yellow Contour line is being increased or decreased (whether the contour patches have been extended or not yet extended). Pick one method of determining the number of control points and contour patches:
By Length radio button and Length decimal field - specifies the distance between control points on the selected Contour line(s), and thus the length of individual contour patches on the selected Contour line(s).
By Patch Count radio button and Patches decimal field - specifies the number of control points on the selected Contour line(s), and thus the number of contour patches along that line (or those lines).
Reset Default button - restores the original Length or number of Patches.
Extension radio button - In this mode, contour patches will be constructed around yellow (extendable) Contour lines.
Factor decimal field (0.1 to an object-specific maximum) - controls the width of contour patches (the distance of the “extension”), measured from the yellow contour line. This value can be changed even after pressing Extend. A change to the Factor affects all extended Contour lines that are selected (but not unextended Contour lines that are selected because those lines have no extension to modify).
Extend button - creates contour patches and subdivision points:
creates contour patches around all yellow (extendable) contour lines. These contour patches are special in that they do not live in panels.
does not create contour patches on orange (unextendable) contour lines, but does create subdivision points on orange contour lines to establish the location of patch corners during subsequent use of Patches > Construct Patches or the Fill All Panels button of Patches > Shuffle > Panels.
Check Path Intersections checkbox (The state of this checkbox is shared with checkboxes of the same name in Contours > Detect Contours, Patches > Construct Patches, Contours > Subdivide/Extend, Patches > Shuffle > Panels, and the Check Geometry checkbox of Grids > Construct Grids) - specifies whether to advise the user, upon completion of this and related functions, whether certain imperfections should be fixed by using Patches > Repair Patches.
OK button - saves the contour patches to the Shape object in the Model Manager and closes the dialog.
Cancel button - terminates the dialog without saving contour patches to the object.
Reset button - re-loads the object from the Model Manager.
Even after you press Execute, both the Factor (width) and the Length of individual contour patches can be adjusted. Click on a yellow contour line (or lines) to highlight all the contour patches associated with it, then adjust the Factor or Length fields, then Ctrl-Click the contour line(s) to un-highlight it. Repeat the process on another yellow contour line if necessary.
Similarly, to modify the extension Factor on only one side of a contour patch, click the black line that forms the edge of a contour patch. Then adjust the Factor parameter and press Enter, then Ctrl-Click the line to un-highlight it. Repeat the process on other black edges of contour patches if necessary.
Similarly, click on an orange contour line, adjust the Length field to change the number of patch corners that will eventually lie on that line, then Ctrl-Click the orange contour line to un-highlight it.