Adding Cues To Views

3.0 Adding Cues To Views

Each view in the project may be annotated with two kinds of Cue

Viewpoint Cues: Each of the edges of the Viewpoint Target (the rectangle of paper on which the object rests), are defined. This is required in order to calculate the Viewing Direction.
Silhouette Cues: The boundary between the object and the scene background is defined. This is required to reliably distinguish between the object and background.

3.1 Adding or Removing a Viewpoint Cue

To add a viewpoint cue first set the viewpoint target type. Select Project->Settings->Cues Tab, the following dialog is shown,

Choose a target type from the dropdown edit labelled Target Type, and if a custom size is chosen fill in the width and height edit boxes.

Then select the Define Viewpoint button on the image toolbar. A help window will be displayed to lead you through the process , close this window if you do not need help. The help window will direct you to select two points on each edge of the viewpoint target (eight points in all). Take care to follow the guidelines below,

Two points are required anywhere on each edge. I.e. anywhere the edge is visible (some of the edges may be partly obscured by the object)
Always start with a long side of the target rectangle, and proceed clockwise around the target. The starting edge is described elsewhere as the Back-Edge of the viewpoint target, and if your object has a back, it may help your understanding if you align it with this edge
Always start with the same edge for each viewpoint in the project. It may be useful to mark one edge of the target to make this easier.

To abort the process select the right mouse button or press the Define Viewpoint button again. You will be asked if you wish to add more points, reply "No" and the unfinished cue is removed.

To remove the viewpoint cue press the Delete View Cue button on the Image Tool Bar

After a cue is defined a viewing direction is calculated, and on this basis an image of the target is projected into the image.

Note that the viewpoint will not be calculated when the Project->Settings->Cues->Calculate Viewpoint on Update checkbox is de-selected. In this case the project will only calculate the viewpoint when the model is built.

If you wish to force the viewpoint to be calculated, or re-calculated, select the Estimate Viewpoint button on the Image Tool-bar.

The image of the target should lie over the target. If this is not the case, the viewpoint is not well defined. Read the instructions again, and attempt to define another cue. If this fails then there is probably a problem with the camera or viewpoint-target information. Read the section on supplying camera information.

3.2 Improving the Viewpoint Cue.

A more accurate fit to the target may be achieved by enabling the Improve viewpoint cue check box. If this is enabled, the position of the cue is automatically adjusted, to lie as close to the image of the target as possible, before a viewpoint is calculated. If this option is enabled the viewpoint cue should be defined so that only visible parts of the target are included. If the cue contains regions which are not visible then the automatically corrected cue may be misaligned with the target.

3.3 Adding One or More Silhouette Cues

Many type of silhouette can be drawn by selecting from the Silhouette Toolbar,

To draw round complicated objects or to draw intricate figures, select the Polygon Silhouette button on the Silhouette Toolbar. Use the mouse to select a point somewhere on the object's boundary. Trace round the object (either clockwise or anti-clockwise is ok). Try to use as few points as possible to get an approximation of the required shape.

To finish adding points press the right mouse button, or press the Polygon Silhouette button again. You can now Remove or edit the silhouette

Note : The first and last points should not lie in the same place. In other words if you draw a triangle only select 3 points, then finish adding points.

You can also draw other types of silhouette,

: Rectangles.
: Ellipses (which includes circles)
: Bezier Curves, which are smooth curves which pass through the points you supply. Supply the points by drawing a closed curve as for the Polygon Silhouette described above.
: Text. Select this and type your text in the text dialog. Choose a font for the text.

3.4 Using a Grid and Guides

To aid in aligning points, or to make exact squares or circles, you may define a Grid and Guides. Select the View->Grid menu option, the following dialog is displayed,

A Grid is a chess-board-like set of squares drawn over each image in the project to aid in the placement of points. Define the number of columns by entering a whole number in the Columns edit box. If you do not want the grid to be made up of squares you can enter the number of Rows, by deselecting the Grid Is Square checkbox.

Guides are not visible, and are used to subdivide each Grid square into smaller grid regions. If the guide Subdivisions = 1 then the Grid is not split any further, if it is 2 then each is split to have 2 columns and 2 rows, and so on.

When you select or move a point of a silhouette in the image, you may want it to jump to the nearest guide-line. This is called Snap-to-Guides, to enable this select the Snap-to-Guides checkbox.

If you move a line or a whole silhouette whilst using Snap-to-Guides, the point of the line or silhouette which is nearest the mouse is snapped.

3.5 Editing Silhouettes

Silhouettes may be Deleted, Moved, Rotated, Re-sized,Converted between types, Cut and Pasted. First select one or more silhouettes.

Selecting a single silhouette : Click on it with the mouse. It will change colour.
Selecting a group of silhouettes : Hold down the Shift key and select a series of silhouettes, they will all change colour. Or select and drag a selection rectangle around the silhouettes, and release the mouse button.

To delete the selection press the delete key; or select the menu option Edit->Delete; or select the Delete button. Undo the action with Edit->Undo

Alternatively use Edit->Cut to remove the silhouette(s) and then paste them into any image using Edit->Paste. Use the Edit->Undo menu option to undo this action.

To Move a selection hold down the CTRL key or press the Move Button and grab the selection with the mouse to move it. To Undo the action, select the Edit->Undo menu option.

To Resize a selection hold down the CTRL key or press the Resize Button and grab a size guide with the mouse to move it. To Undo the action, select the Edit->Undo menu option.

To Rotate a selection press the Rotate Button. A dialog is shown which allows you to specify the rotation. To Undo the action, select the Edit->Undo menu.

To Convert a selected silhouette, use the Tools->Convert Silhouette menu option. Any silhouette may be transformed into a number of outher types. For example, a polygon may be converted into a Bezier curve, or a rectangle could be converted into an ellipse.

3.6 Editing Points and Lines

Individual points and lines may be Added, Deleted or Moved. First select an item,

Selecting a line : After selecting the line's silhouette click on the middle of the line, the line and it's endpoints are highlighted.
Selecting a point : After selecting a silhouette, click near to a silhouette point to highlight it.

To Delete the selection press the Del key or Delete button, or choose the Edit->Delete menu option. The deletion may be Undone using the Edit->Undo menu option.

To Move the selection hold down the CTRL key or press the Move button, and grab the selection with the mouse to move it. To Undo the move select the Edit->Undo menu option.

To Add Points to existing silhouettes, select a line in which new points are to be added, then press the Add Points button. Add the new points and then press the right mouse button, or Add Points button, to finish adding points.

TIP : When defining cues, bear in mind that the image magnification may be changed at any time to simplify the accurate placing of points.

3.7 Silhouette Properties

Select a silhouette or several silhouettes, and either select the right-menu Properties menu item, or the View->Properties menu item. The following dialog box is shown.

These are the silhouette's properties. The Silhouette Type gives the name of this kind of silhouette, i.e. Polygon, Ellipse, Rectangle, or Bezier.

If the silhouette is an Ellipse then you may edit the Number of Points field, to the required number of points for the ellipse. You cannot edit this field for other types of silhouette.

If Include in shape definition is checked (this is the default value) the silhouette is used to modify the model's shape when generating the 3D model. If Include in viewpoint definition is checked (this is the default) then the silhouette may be used in calculating the viewing position for the view in which it lies.

Note that if the image->properties-> Use silhouettes from this image to infer shape is not checked then the silhouette will not be used to infer shape, even if this option is selcted in the above properties - this option overrides individual silhouette's properties.

Silhouette Group is an integer number between 0 and 99, with a default of 0. Silhouettes with the same group number are used together to infer 3D shape. See more about groups here

Note that each silhouette group must have at least two members, and the members cannot all be in just one image.

TIP: In many models a single group is sufficient, and initially it is best to start a project with just a single group, with further groups added later if needed.

If the silhouette is of type Bezier then you may adjust the smoothness of the curve using the Bezier Smoothness slider control. Smoother curves will contain more points.