On screen controls

form•Z makes extensive use of on screen controls to modify objects, textures and other entities.


Many objects, such as spheres, cubes, and extruded shapes maintain their generation parameters. They are called controlled objects. Their control parameters may be shown on the screen through simple graphic controls, which allow the user to edit the shape of the object. For example, an extruded object shows an arrow for the extrusion height. Clicking in the arrow tip interactively changes the height of the extrusion by dragging the cursor along the arrow direction.


Object controls are shown right away when the object is created. For example, drawing a sphere shows its controls after the interactive generation is completed. The user may now refine the shape by using the on screen controls. Leaving the generation tool, turns the controls off.


Object controls may be turned on and off with the Pick, Pick Part, or Area Pick tools. For example, after a sphere was drawn, activate the Pick tool. This will remove the sphere’s controls. Now pick the sphere and click on the Show Controls button at the bottom of the Tool Options palette. This will turn the controls on for all selected objects. The controls will stay enabled until they are specifically turned off again by clicking on the Hide Controls button.


Most tools have no use for object controls. For example, after turning object controls on with the Pick tool, you switch to the Boolean Union tool, the controls will be hidden, as they have no meaning for this tool. Switching back to the Pick tool will show the controls again.


There are two types of controls: free moveable point controls and constrained controls, such as arrows. These are manipulated in different ways.


Constrained controls

After the object controls are enabled with the Pick tool, the user may click in the “hot spot” of the control. This is indicated by the editable part of the control turning to the highlight color (red), when the cursor rolls over the part. For example, the extrusion height control consists of an arrow, starting from a base point, along a line, with a tip at the end. The tip is the hot spot. Clicking in the hot spot starts the interactive editing. In this case the tip is moved along the arrow direction, defining a new height. Clicking a second time ends the interactive editing. This method allows for only one such control to be edited at a time.


Picking such a control also automatically selects the object to which it belongs and the object’s parameters are shown in the Parameters tab of the Tool Options palette. While the control is manipulated, the corresponding parameter in the palette is highlighted and its value is updated. For example, the height value of an extruded object is updated in the Parameters tab, as the height is changed through the control. Typing a value while the control is edited and hitting the tab or return key will end the control editing and use the typed value instead. This allows for a combination of graphic and numeric editing without having to move the mouse into a specific text field to activate it.


Free moveable point controls

As the constraint controls, these have a hot spot, which highlights when the mouse is moved over it. Clicking on it starts moving the point parallel to the current reference plane. Hitting and releasing the command key (Mac) or ctrl key (Windows) switches the direction to / from the perpendicular direction of the reference plane. A second click ends moving the point, which remains selected. Unlike constraint controls, multiple controls can be picked by holding down the shift key. This is the same method as picking multiple objects, except that shift needs to be pressed even for the first of several points that will be picked. Free moveable points are used primarily as the controls of spline curves and surfaces and end points of lines and arcs.


Free moveable point controls can also be modified with the Move, Rotate, Scale, and Mirror transformation tools, as well as the Delete tool. For example, you may pick several control points of a spline curve with the Pick tool. Then switch to the Move tool. You notice that the controls are still shown. Now move the controls by clicking a start and end point.


As with picking objects, if there are multiple controls on top of each other, they can be toggled by placing the cursor over the controls and then hitting the tab key. With each key stroke, the next control is highlighted. After the desired control is reached, the mouse is clicked to select the control.


A Perpendicular to Surface guide is available when editing control points of NURBS surfaces. When clicking a control point to move it, a snap guide is shown that is perpendicular to the surface, through the control point. This allows the control point to be easily moved closer to, or further from, the surface. This guide is also available when moving NURBS control points with the Pick tool.