3. Modelling Actions

This section contains the documentation of the interactive modelling actions available in Ayam.

Before invoking any modelling action one or more objects should be selected using the object hierarchy in the main window, the pick action, or selection manipulating keyboard shortcuts.

Every action can be started with a key press (a shortcut) when the keyboard focus is in a view window or by clicking on the associated button in the toolbox window. Using a keyboard shortcut starts that action in the current view only, the other views are not affected. In multi window GUI mode, starting an action from the toolbox window will cause the action to be started in all view windows that are currently open simultaneously. In single window GUI mode, the action will be started in the current internal view only (unless "AutoFocus" is enabled).

It is perfectly ok to start and work with many different actions at the same time in different views: one can have e.g. a view, where objects are moved, a second where objects are rotated and a third, where objects are picked. The layout, drawing style, and grids may also differ between the different views. Together with the feature, that the selection may be changed while actions are active and even panning and zooming of views is possible (using the rightmost and middle mouse buttons respectively) while actions are active and without breaking them, this is the key to unsurpassed flexibility in modelling using Ayam.

To break an action, the <Esc> key may be used.

The default action for all views, which is also in effect after use of the <Esc> key, is "None" or "Pick" (depending on the preference setting "Modelling/DefaultAction"). See section Selecting Objects by Picking for more information about picking objects.

Note that the modelling actions are not available in perspective views.

If an action is in effect for a view, the views title will be changed appropriately.

A modelling action is performed by clicking into the view with the leftmost mouse button to mark a point in space or to pick a vertex and then by dragging the mouse.

You may undo/redo the effects of a modelling action using <Ctrl+z> and <Ctrl+y> (see section The Undo System for more information).

Grids are available to restrict the modelling actions to certain points and help in exact modelling.

Also note that the middle and rightmost mouse buttons may be used to zoom and move the view while modelling actions are active.

For actions that modify the camera of a view please see section View Window Shortcuts and Actions.

3.1 Modelling Actions Overview

This section gives an overview over the various modelling actions. Note that a more complete collection of shortcuts is available as separate reference card document in the Ayam distribution.

Name	Shortcut	Icon	Name	Shortcut	Icon
Transform:
Move	<m>		Rotate	<r>
Move X	<mx>		Rotate About	<ra>
Move Y	<my>		Set Mark	<a>
Move Z	<mz>
Scale 3D	<S>		Scale 3D About	<Sa>
Scale 2D	<s>		Scale 2D About	<sa>
Scale 1D X	<sx>		Scale 1D X About	<sxa>
Scale 1D Y	<sy>		Scale 1D Y About	<sya>
Scale 1D Z	<sz>		Scale 1D Z About	<sza>
Stretch 2D	<T>		Stretch 2D About	<Ta>
Edit:
Edit	<e>		Tag Points	<t>
Edit Weights	<w>		Insert Points	<i>
Edit Numeric	<E>		Delete Points	<d>

3.2 Transforming Objects or Selected Points

Many modelling actions either work on objects transformation attributes or coordinates of selected points. Before Ayam 1.18 this was controlled implicitly by the point selection: if points were selected, they would be transformed instead of the object.

There are now two keyboard shortcuts (<o> and <p>) that let the user control this behaviour directly per view:^[*^] <o> switches to object transformations and <p> to point transformations. These shortcuts can be used anytime, even in the middle of any other actions. If points are to be modified, a little red point will appear in the modelling mode icon in the view menu as shown in the image below:

Note that those shortcuts just switch the current view, to modify all open views, just press o or p twice: <oo> and <pp>.^[*^]

See also the section Automatic Point Actions for a script, that, partially, brings back the old implicit behaviour.

3.3 Selecting Objects by Picking

This section describes techniques that can used for selecting one or more objects within a view window with the mouse.

When the view windows action is "Pick", objects that appear within this view can be selected with the mouse. This action may be invoked by pressing <P> or by making this action the default action using the preference setting "Modelling/DefaultAction". If picking is the default action, it will be automatically enabled when any other action is broken using <Esc>.

Selecting Individual Objects

Selecting objects within a view is a straightforward operation that uses standard methods. You will use the following two selection operations most frequently:

• To select a single object within a view, move the cursor to the object and click mouse button 1 (the leftmost one). Once you select an object, any objects previously selected are unselected automatically.
• To select an additional object, move the cursor to the object and <Control>+Click (again with the leftmost mouse button). Previously selected objects remain selected, and the newly picked object is added to the selection. Notice that the picked item must belong to the same level as the previously selected objects. An alternative method for selecting multiple objects is to drag a rectangle around them. For more information see Drag-selecting Multiple Objects

Note that the Root object and View objects can not be pick-selected at all.

Drag-selecting Multiple Objects

You can select multiple objects using the <Control>+Click method described in section Selecting Individual Objects. An additional method for selecting multiple objects is to drag a rectangle around those objects. However only objects that belong to the current level can be picked within a drag-selection. If you want to select multiple objects that belong to another level you must change the current level by either selecting it in the tree/listbox or by picking one object from that level on a view.

The procedure for drag-selecting multiple objects also uses a standard method:

1. Imagine a rectangle that encloses only the objects you want to select.
2. Click at one corner of the rectangle and, while continuing to press the mouse button, drag until you have enclosed all the objects.
3. Release the mouse button. All the valid objects inside or crossing the rectangle are selected and any objects previously selected are unselected automatically.

Note that if you press <Control> during the drag-selection, objects that are enclosed by the rectangle will be added to the current selection instead of replacing it.

Ambiguous Picking

In some cases Ayam is unable to differentiate between the objects you have selected and other nearby or related objects. This ambiguity can arise as follows:

• Imagine a small square surrounding the cursor. When you click an object, any other valid objects that fall inside this square are also considered to be possible selections. For example, if you select an item that is positioned very close to another one, Ayam may consider both items to be possible selections.
• If your model is three-dimensional (which is likely to happen), imagine a line that is perpendicular to the screen and that passes through the cursor and into the model. When you pick an object, any objects that intersect this line are considered to be possible candidates for selection.

If the selection is ambiguous Ayam displays a window that contains a list of the possible candidates for selection (see image below), or, if the "PickCycle" option is activated, Ayam just cycles through the candidate objects by further clicks on the same position.^[*^]

When a name in the candidate list is selected, the corresponding object is highlighted. Click "Ok" when you have determined which object to select or "Cancel" to close the list and keep the previous selection unchanged.

It is also possible to use a double click in the list of selection candidates to select an object and immediately close the dialog window. Moreover, as the list of candidates immediately gets the keyboard focus, the cursor keys and <Enter> can also be used to select the object.^[*^]

Notes:

• While the list of ambiguous candidates is opened no other objects can be picked within the views.
• It is possible to use the "Zoom to Object" action (shortcut <O>) while the ambiguous select listbox is open to get a better view of the temporarily selected object.
• The tolerance used to determine whether an object should be picked or not can be adjusted (see "PickTolerance" in Hidden Preference Settings).

3.4 Moving Objects or Selected Points

Using the modelling action "Move" (shortcut: <m>) selected objects or selected (tagged) points can be moved.

Note that the objects/points will be moved in the XY-plane for Front-views, the ZY-plane for Side-views, and the XZ-plane for Top-views only, no matter how the view is rotated.

The move action may be restricted to a certain axis, by pressing <x>, <y>, or <z> right after the <m>.^[*^]

For an overview of the move actions see also the table below.

Name	Shortcut	Icon
Move	<m>
Move X	<mx>
Move Y	<my>
Move Z	<mz>

3.5 Rotating Objects or Selected Points

Using the modelling action "Rotate" (shortcut: <r>) objects or selected (tagged) points can be rotated.

The axis of rotation is always parallel to the Z-axis in Front-views, the Y-axis in Top-views, and the X-axis in Side-views of the local object coordinate system. The orientation of the object coordinate system may change in respect to the world coordinate system if a sequence of rotate modelling actions is applied.

Note that if multiple objects are selected, each object is rotated around the center of its own local coordinate system. Only the Rotate_X, Rotate_Y, or Rotate_Z property of the selected objects will be changed by this action.

Name	Shortcut	Icon
Rotate	<r>

3.6 Rotating Objects or Selected Points about a Point

Using the rotate about modelling action objects or the selected (tagged) points of the selected objects can be interactively rotated about a specific point in space.

To start the rotate about action, invoke the normal rotate action, then press <a>. See also the table below.

Name	Shortcut	Icon
Rotate About	<ra>

To rotate about a different point, the intermediate set mark action must be restarted (simply press <a> again).

After setting the mark, the action works the same way as the Rotate action, except that it rotates the selected object(s) or points about the mark. This, consequently, also works with multiple selected objects. Note that this action does not only change the Rotate_X, Rotate_Y, or Rotate_Z properties of the selected objects, but also the Translate_X, Translate_Y, or Translate_Z properties.

To avoid degenerated coordinates due to roundoff errors it is highly suggested to use grids with this action.

See also the section Automatic About Center Actions for a script, that modifies the rotate action to rotate about the current selections center automatically.

3.7 Scaling Objects or Selected Points

There are several different actions available to interactively scale objects or the selected (tagged) points of the selected objects:

The modelling action "Scale 3D" (shortcut: <S>, note the big S!) scales all three axes of the selected objects or the selected (tagged) points of the selected objects by the same factor.

The modelling action "Scale 2D" (shortcut: <s>) scales just two axes of the selected objects or the selected (tagged) points of the selected objects. Those axes are XY in a Front-view, ZY in a Side-view, and XZ in a Top-view.

It is also possible to restrict the scaling of objects or selected points to just one axis. For that <x>, <y>, or <z> must be pressed right after <s> (e.g. <sx> for scale 1D about x).

Since Ayam 1.17, direct access to the 1D scale modelling actions "Scale X" (old shortcut: <x>), "Scale Y" (old shortcut: <y>), and "Scale Z" (old shortcut: <z>) is no longer available.

The modelling action "Stretch 2D" (shortcut: <T>) works much like "Scale 2D" but the scale factor for each axis may be different. Never start this action by a click near one of the axes to be changed, as this will cause very big scale factors for the other axis. Try it first with a centered box by starting from one of the box corners, then try it once starting on the X-axis.

For an overview of the scale actions see also the table below.

Name	Shortcut	Icon
Scale 3D	<S>
Scale 2D	<s>
Scale 1D X	<sx>
Scale 1D Y	<sy>
Scale 1D Z	<sz>
Stretch 2D	<T>

3.8 Scaling Objects or Selected Points about a Point

Using the scale about modelling actions objects or the selected (tagged) points of the selected objects can be interactively scaled about a specific point in space.

To start a scale about action, invoke the normal scale action, then press <a> (e.g. <sa> for scale 2D about, <sya> for scale 1D Y about). For an overview of the scale about actions see also the table below.

Name	Shortcut	Icon
Scale 3D About	<Sa>
Scale 2D About	<sa>
Scale 1D X About	<sxa>
Scale 1D Y About	<sya>
Scale 1D Z About	<sza>
Stretch 2D About	<Ta>

To scale about a different point, the intermediate set mark action must be restarted (simply press <a> again).

After setting the mark, the action works the same way as the scale action, except that it scales the selected object(s) or points about the mark. This, consequently, also works with multiple selected objects. Note that this action does not only change the Scale_X, Scale_Y, or Scale_Z properties of the selected objects, but also the Translate_X, Translate_Y, or Translate_Z properties.

Also note, that the three dimensional scaling about the mark occurs in all three dimensions, however, in the intermediate interactive set mark action only two dimensional coordinates can be specified using a single mouse click. To specify a true three dimensional mark the corresponding view object attributes can be used or a point can be selected and the mark set to it (shortcut <C>). See section Setting the Mark for other means of setting a three dimensional mark.

To avoid degenerated coordinates due to roundoff errors it is highly suggested to use grids with this action.

See also the section Automatic About Center Actions for a script, that modifies the scale actions to scale about the current selections center automatically.

3.9 Setting the Mark

This action may be invoked to mark a point in space for perusal of other modelling actions that e.g. rotate or scale about a point.

The keyboard shortcut to invoke the set mark action is <a>. This action is also active as intermediate action for e.g. rotate about, where the keyboard shortcuts <r> and then <a> would be used in a sequence and after setting the mark, the rotate about action would take over.

See also the table below.

Name	Shortcut	Icon
Set Mark	<a>

A single click with the mouse sets the mark. If grids are active in the view, the mark will be snapped to the nearest grid coordinates. Note, that, using a single mouse click, only two dimensional mark coordinates can be specified. Therefore, in versions prior to 1.21, the third coordinate was always set to zero upon a click. This is no longer the case. If the preference option "Modelling/GlobalMark" is enabled, the third coordinate is not reset anymore. This way all three coordinates of the mark can be defined by clicking two times in appropriate views, e.g. first in a front view for the x and y coordinates and then in a side view for the missing z coordinate.

The mark can also be set to a point of one of the selected objects. In this case, the mark coordinates are always immediately three dimensional.^[*^]

Additionally, when the set mark action is active, the following keyboard shortcuts are available:

• <Return> accept the current mark (useful, if one first rotates about a point then decides to also scale about the same point: <ra>, drag mouse, <sa>, <Return>, drag mouse ...),
• <c> set the mark to the center of gravity of all currently selected objects coordinate systems,
• <C> set the mark to the center of gravity of all currently selected points.
• <B> set the mark to the center of the bounding box of all currently selected points. The image below demonstrates the difference between the center of the bounding box and the center of gravity.

The mark may also directly be manipulated using the corresponding view object property (see also section ViewAttrib Property).

Since Ayam 1.21, the mark may also be set without activating the set mark action and without interfering with other modelling actions by double clicking with the rightmost mouse button.

Another way of setting the mark is via the "FindU" special action for curves (see also section Finding Points on Curves) or the "FindUV" special action for surfaces (see also section Finding Points on Surfaces) .

The mark can also be used to remember an important point in space and get back to it later using the pan to mark action (keyboard shortcut <.>).

The current mark can be cleared by pressing <D> anytime.

Finally, remember that certain operations like e.g. changing the view type will also clear the mark.

3.10 Selecting/Tagging Points

The modelling action "Select Points" (shortcut: <t>; for t ag points) may be applied to objects that support single point editing or read only points.

To select or de-select a point it can directly be clicked upon or a rectangular region can be dragged with the mouse around the points in question.

Only points within a certain distance from the mouse pointer click position will be considered picked (see preference option "Modelling/PickEpsilon"). Points that would be picked will flash in a different color when the mouse pointer moves over them (this is also controlled by the preference option "Modelling/FlashPoints").

Selected points will be drawn in dark red when the select points modelling action or a modelling action that would modify the selected points is active (see the following image).

The selected editable points may be modified subsequently using the modelling actions Move, Rotate, and Scale as discussed above when the view is switched to point transformations using the shortcut <p>. See also the table below.

Name	Shortcut	Icon
Tag Points	<t>

After the pick (the selection of a point), the picked point will be added to the list of selected points for the selected object. If the selected point is already in that list it will be removed from the list instead, the picked point will be deselected.

All points can be selected easily using the keyboard shortcut <A>.

The list of selected points will not be deleted from the object until an explicit deselection is performed using the keyboard shortcut <N> or if certain modelling tools are used.

The point selection can also be inverted using the keyboard shortcut <I>.

All three shortcuts above can be used anytime without interfering with any other active modelling actions.

Note that the list of selected points is not copied, if the object is copied using the clipboard. The selection is also not saved to Ayam scene files. But selected points survive undo/redo.^[*^]

Furthermore, the selection action itself is not an operation recorded in the undo buffer, thus cannot directly be undone.

The point selection also does not interfere with single point modelling actions: It is perfectly legal to select some points, move them using the move action, then switch to single point editing, edit some other or even one of the selected points, switch back to the selection action, add other points to the selection or delete some points from the selection, switch to rotate, rotate the selected points and so on.

A bigger number of points may be added to the selection using a click and drag operation. All points that are inside the rectangular region defined by the click and drag will be added to the selection. In fact, this approach is the only way to safely add points to the selection that occlude each other. Clicking always only adds/removes single points.

Holding down the <Ctrl>-key while dragging the mouse removes all selected points within the rectangular region defined by the drag from the selection.^[*^]

The exact behaviour of picking multiple points of a NURBS curve or surface depends on the attribute "CreateMP":
If "CreateMP" is enabled, picking a multiple point will always select all points that make up the multiple point.
If "CreateMP" is disabled, picking a multiple point will only select the first of the points that make up the multiple point (but drag selection can be used to select all points nevertheless).

3.11 Editing Points

To edit the points of an object four actions ("Edit", "Edit Weights", "Reset Weights", and "Numeric Point Edit") are available. All those actions may be applied to objects that support single point editing only. Such objects usually draw their selectable points using small white rectangular handles when a modelling action is active (see also the image below).

In contrast to e.g. the move action, all point edit actions require the handle of the point to be picked directly. Only points within a certain distance from the mouse pointer click position will be considered picked (see preference option "Modelling/PickEpsilon"). Points that would be picked will flash in a different color when the mouse pointer moves over them (this is also controlled by the preference option "Modelling/FlashPoints").

For an overview of the point edit actions see also the table below.

Name	Shortcut	Icon
Edit	<e>
Edit Weights	<w>
Reset Weights	<W>
Numeric Edit	<E>

• The modelling action "Edit" (shortcut: <e>) works much like the move action, but it moves single points instead of objects. Since Ayam 1.18 it is possible to edit points of multiple selected objects (in former versions only points from the first selected object were considered).

  If a multiple point is edited, this action modifies all single points that make up the multiple point, i.e. you can not move single points apart from a multiple point using the point edit action. Temporarily disable the "CreateMP" property or explode the multiple point to do that.

  If the preference option "Modelling/EditSnaps" is enabled, the picked point will be moved to the nearest grid coordinates first, otherwise the grid just controls the displacement for the edit action. The snapping can occur in 2D or 3D, depending on the preference option "Modelling/Snap3D". Moreover, while snapping a point, the mouse pointer will warp to the new position of the point (so that the user does not lose track of it). Warping the mouse pointer currently does not work on MacOSX Aqua.

• The modelling action "Edit Weights" (shortcut: <w>) changes the w coordinate of a single point by dragging the mouse left or right.
• The modelling action "Reset Weights" (shortcut: <W>) resets the w coordinate of the picked point to 1.0.

  The weights may be reset for all points using the shortcut: <Ctrl-W>.

• The modelling action "Numeric Point Edit" (shortcut: <E>) starts an intermediate point selection action and upon a click with the mouse opens a small window where the coordinates of the selected editable point(s) may be changed directly by entering new coordinate values on the keyboard (see image below).
  
  Numeric Point Edit Dialog

  Nothing will be changed unless the "Return" key is pressed in a coordinate entry field or the "Apply" button is used. In contrast to the normal point selection action, clicking on new points, while the edit point dialog is open, deselects the old point(s), selects the new point and loads its coordinate values into the entry fields. In case of multiple selected objects, the deselection is only performed on the object with a new selection.

  Note that the w coordinate setting will be ignored for selected points that do not have weight information (are not rational).

  Using the small menu on top of the coordinate window one can determine whether editing takes place in local/object space or global/world space.

  This modelling action may affect multiple points of multiple selected objects.^[*^]

  Snapping points of different objects together is now possible too: Just select two objects, start numeric point editing (press <E>), pick a point on the first object (where a point of the second object should be snapped to), the point edit window opens, now drag select the point of the second object (do not use a single click for selection as this would also load new coordinates) and press apply.

  The numeric point editing action also supports read only points, their coordinates may be retrieved, but applying any values will have no effect.^[*^]

  When applying changes, single coordinate entry fields may be empty to prevent a change of the corresponding coordinate value.^[*^]

  If a multiple point is edited, this action modifies all single points that make up the multiple point, i.e. single points can not be moved apart from a multiple point using the numeric point edit action. Temporarily disable the "CreateMP" property or explode the multiple point to do that.

  Notice that the numeric point editing dialog may stay open all the time.^[*^]

  Furthermore, it is not necessary that the original object stays selected while working with the numeric point edit dialog, other objects may be selected to e.g. infer new point coordinates from their properties and apply them to the original object. Furthermore notice that the coordinate values displayed in the numeric point editing window will not update when the point is modified by another modelling action (e.g. in another view). Simply click on the point again in a view where the numeric point editing action is active, to update the coordinate values in the numeric point editing dialog.

  The numeric point edit value fields support Tcl expressions. This allows e.g. to set a point to exactly^[*^] 1/3 by entering:

  [expr 1.0/3.0]

  Even though the dialog may display point coordinates in degraded accuracy (due to floating point to string conversion) the original point data is unchanged and its accuracy is not affected as long as the new data is not applied. See also the discussion of the "TclPrecision" preference option in section Miscellaneous Preferences).

  The numeric point edit dialog also has a context menu.^[*^] The entries in this menu allow to:

  • "Clear" all entries,
  • "Reset" all entries to the last fetched values (undo edits), or
  • "Fetch Mark", set all entries to the mark coordinates of the current view (W is cleared).

3.12 Snapping Points to the Grid

There are two actions available for snapping points to the current grid of a view.^[*^]

The actions are initiated using the shortcuts <g> and <G>. If an object has selected (tagged) editable points, only those points will be snapped to the grid, otherwise all editable points of the object will be snapped to the grid (see also the image above). If <g> is used, the snapping only occurs in the modelling plane associated with the view (i.e. in 2D). To snap all three coordinate values to the grid use <G>. Note that the snapping also occurs, if the view has the preference option "Use Grid" turned off. This action can be used without affecting other active actions.

3.13 Snapping Points to the Mark

The snap points to mark action moves all selected points to the current mark.^[*^]

This action is initiated using the shortcut <M>. All selected editable points of the selected objects are snapped to the current mark coordinates (see section Setting the Mark for more information about the mark) immediately. This action can be used without affecting other active actions. See also the image above.

3.14 Snapping Objects to the Mark

The snap objects to mark action moves all selected objects to the current mark.^[*^]

This action is initiated using the shortcut <K>. All selected objects are snapped to the current mark coordinates (see section Setting the Mark for more information about the mark) immediately, providing an easy way to move objects over long distances or to just put an object "here". This action can be used without affecting other active actions.

3.15 Inserting or Deleting Points

The modelling action "Insert Point" (shortcut: <i>) may be applied to NURBS, interpolating, and approximating curves (objects of type NCurve, ICurve, and ACurve) only. A new control point will be inserted in the curve right after the picked point. The new point will be inserted in the middle between the selected point and the next point, changing the shape of the curve. It is also possible to insert control points into certain types of NURBS curves without changing their shape using knot insertion; see also the insert knot tool section Insert Knot Tool.

The modelling action "Delete Point" (shortcut: <d>) may be applied to NURBS, interpolating, and approximating curves (objects of type NCurve, ICurve, and ACurve) only. The selected control point will be deleted from the curve. Deleting points from a curve with knot type "Custom" may currently lead to an incorrect knot sequence, please check and correct the new sequence manually. See also the table below.

Name	Shortcut	Icon
Insert Points	<i>
Delete Points	<d>

3.16 Manipulating the Multiplicity of Points

To manipulate the multiplicity of selected NURBS curve control points there are two modelling actions available.^[*^]

The actions are initiated using the shortcuts <*> (to increase the multiplicity) and </> (to decrease the multiplicity).

Increasing the multiplicity of a control point can be used to easily construct sharp corners and linear curve segments (see also the image above).

The multiplicity of the selected control points will only be raised to the order of the curve and, conversely, never be decreased below 1. Trying to increase/decrease beyond those limits will not result in any error.

The selected points stay selected, so that the actions can be applied multiple times.

Both actions can be invoked anytime without breaking other actions.

3.17 Finding Points on Curves

The modelling action "FindU" (shortcut: <u>) may be applied to NURBS curves (objects of type NCurve or objects that provide NCurve objects) only. This action may be used to get the corresponding parametric value u from a point on a curve. For every picked point the appropriate value for u is calculated, stored in the global variable u, and additionally written to the console. The mark is set to the position of the picked point (see section Setting the Mark for more information about the mark). Remember to exactly pick a point on the curve or nearby, otherwise the calculation may fail. See also the table below.

Name	Shortcut	Icon
Find U	<u>

3.18 Finding Points on Surfaces

The modelling action "FindUV" (shortcut: <U>) may be applied to NURBS surfaces (objects of type NPatch or objects that provide NPatch objects) only. This action may be used to get the corresponding parametric values u and v from a point on a surface. For every picked point the appropriate values for u and v are calculated, stored in the global variables u and v, and additionally written to the console. The mark is set to the position of the picked point (see section Setting the Mark for more information about the mark). Remember to exactly pick a point on the surface or nearby, otherwise the calculation may fail. As the icon suggests, this action works best in the shaded drawing mode. See also the table below.

Name	Shortcut	Icon
Find UV	<U>

3.19 Interactively Splitting Curves

The modelling action "Split Curve" (shortcut <c>) may be applied to NURBS curves (objects of type NCurve) only. Using this action a NURBS curve may be split into two new curves at a point on the curve that is specified by picking a point on the curve.
Remember to exactly pick a point on the curve or nearby otherwise the calculation of the parametric value for the split will fail. The selected curve will be changed by this action, and a new curve will be created. It is currently not possible to undo the changes of a split!

3.20 Selecting/Tagging Boundary Points

The modelling action "Select Boundary Points" (shortcut <b>) may be applied to PolyMesh objects only.
This action can be used to select all control points of a PolyMesh boundary after picking a point on that boundary.^[*^] Note that the PolyMesh object must be optimized for best results. See also the table below.

Name	Shortcut	Icon
Select Boundary	<b>

3.21 Editing in Local Spaces

Normally, all editing takes place in world space and the input plane of all modelling actions is constrained to the world XY-, ZY-, or XZ-plane (depending on the type of view used).

However, if a view is aligned and switched to local, editing in local object space is possible. This means a planar parameter curve of a Skin object may be edited where both objects are rotated and scaled arbitrarily via their transformation attributes and the parameter curve is guaranteed to remain planar all the time.

In other words, the input plane of an aligned local view will match the XY-, ZY-, or XZ-plane of the local object space, depending on the type of the view ("Front", "Side", or "Top"). Editing and other modelling actions take place in that plane.

Furthermore, grids will also act as if defined in local object space. Note that in contrast to their normal behaviour, grids can also be scaled differently in X-window and Y-window coordinates in aligned local views (if the local object space is deformed this way).

To make a view object local and aligned the object must be selected first. Now, pressing <l> twice makes the current view local (in external views <Ctrl+l> can also be used). In Ayam versions prior to 1.18 the view also needed to be aligned manually using <L> (or <Ctrl+a> in external views). Since Ayam 1.18, the view is automatically aligned to the selected object or current level when cycling through the global/local modes. Manually aligning a view may still be necessary after certain changes to the the camera of the view e.g. by the rotate view action. Note that realigning is also always possible by cycling the modelling mode three times using <l>. But let us get back to our local view.

To illustrate local views a little bit further, see the following example images:

A Sweep object with a circular B-Spline curve as cross section (rotated about the y axis by 90 degrees using the transformation attributes) and a straight standard curve as trajectory. The Sweep itself is rotated about the z axis by 30 degrees. The view is a front view, the cross section and trajectory are both selected. Note how inadequate the grid spacing would be to edit the trajectory curve (it is e.g. near impossible to edit the curve and keep it straight).

» Press <l>.

The view has been switched to level-local using a single press of the <l> key (see the modelling mode icon, it is displaying a L in the lower right corner. The view is now aligned to the 30 degree rotated space of the Sweep object (note the Root object coordinate system, it is tilted). The grid is also rotated (with respect to the root coordinate system) but now much more useful for editing the trajectory, in fact it is perfectly aligned to the trajectory.

» Press <l> again.

Now the view is object-local and aligned to the first of the selected objects (the cross section curve); look at the modelling mode icon, it is now displaying a O in the lower right corner. As the selected cross section curve was rotated by 90 degrees around the y axis, the front view now displays a circle. Note again the orientation of the Root object coordinate system. The cross section curve can now be edited safely, it will stay planar.

Note, that object-local aligned views only align to the first of multiple selected objects; if all selected objects share the same transformation attributes, everything is fine, but if not, some objects will be misaligned.

Also remember: when a view is level-local, changing the current level does not automatically realign the view. If the view is object-local, changing the object selection will also possibly lead to a misaligned view. To realign the view after changing the current level or object selection simply press <L>. Note that aligning the view changes the aim point of the view camera to the origin of the respective local coordinate system which might not be appropriate for modelling purposes; so, after a selection change, one may want to also zoom the view to the newly selected object: <LO>.

Finally, note that aligning views only works for spaces defined by the transformation attributes, it is not possible to align to e.g. a planar curve that has the default transformation attributes and is rotated via the control points.