Interactively Editing Surfaces

Selecting Control Polygon Rows and Columns

Figure 1, The Mesh Edit Selector for choosing the currently edited control polygon column or row.

By default, all the control polygon vertices of a surface mesh are editable. However, for detailed editing it is possible to work with a single column or row of the surface. In these cases, the currently selected column or row is displayed schematically in the Mesh Edit Selector, (Figure 1), with U columns running down the screen and V row running across the screen. The selected row or column can be changed by clicking on one of the lines in the display. Note that, while surfaces create in PolyCAD should be visually orientated similarly to the lines in the Mesh Edit Selector, parametrically generated surfaces or those from other sources may be orientated differently. However, commands for re-orientating the surface can be found on the entity right-click menu.

Controls

All the points of the control polygon can be selected and edited. During manipulation, the surface is simplified, i.e. less parameter lines are drawn, to ensure editing remains smooth.
Only the control polygon points on one U column can be selected and edited. The exact column can be selected by clicking on one of the lines in the mesh edit selector display or by using the arrow buttons in the edit points section of the Entity Attribute Panel.
Only the control polygon points on one V row can be selected and edited. The exact row can be selected by clicking on one of the lines in the mesh edit selector display or by using the arrow buttons in the edit points section of the Entity Attribute Panel.
For BSpline Surfaces, subdivides the surface adding more control polygon U columns. The global version of the Oslo subdivision algorithm is used maintaining a uniform knot vector.
For BSpline Surfaces, subdivides the surface adding more control
polygon V rows. The global version of the Oslo subdivision algorithm
is used maintaining a uniform knot vector.
Add a U column to the control polygon. Press the button, the click
between the lines of the mesh edit selector to locate where the column
should be added.
Add a V row to the control polygon. Press the button, the click
between the lines of the mesh edit selector to locate where the row
should be added.
Removes the current column or row from the control polygon.

Selecting Edit Points

On entering an entity's edit mode, the control points of a surface will be marked by small circles. Control points are manipulated by dragging the mouse when they are selected. Points are selected using exactly the same approach as the selection of entities. Individual points can be selected by Left-Clicking on the points, (Figure 2). If no point for selection is found, region mode will be automatically entered, (Figure 3). Additional points can be added to the selection set by pressing the Ctrl key. Region selection mode can be entered directly by pressing the Shift key. Both the Ctrl and Shift can be used together interchangeably. Points are also selected when the user selects cells of the coordinate grid in the Entity Attribute Panel.

Figure 2, Point Selection.
Figure 3, Region Selection.

Points Manipulation

Once a point or set of points has been selected, with the Left-Click button still down the points can be either manipulated using the Enhanced 3D Editing mode or in the plane of the current screen view with 3D Mode off. Pressing the control key will constrain the movement of the point to the closest axis direction, (Figure 4). Points can also be manipulated using the arrow keys with 3D Editing on or off. When 3D Editing is off points will move in the screen plane. The distance moved by each press of the key is defined by the Key Nudge parameter in the PolyCAD Options Panel -> Manipulation Options.

Figure 4, Point manipulation is constrained to the axis directions by pressing the Ctrl key.

Editing Surface Control Points Numerically

The individual coordinate components of each control point can be edited numerically from the grid in the Entity Attribute Panel. When a point is selected in the coordinate grid it is show highlighted in the model view. In addition, to editing individual coordinates, points can be added, removed, copied using the following tool buttons above the grid.

Controls

Edit the U columns of the control polygon. The grid displays the coordinated for the currently selected column.
Edit the V rows of the control polygon. The grid displays the coordinated for the currently selected column.
Opens the Fill Values dialog box which set the selected coordinate component of all the control points in the grid to the same value.
Selects the previous column or row.
Selects the next column or row.
Copies the control point coordinates values to the windows clipboard for pasting into a spreadsheet for example.