3.4.1. Viewing the image

To load a mask into this window, you can either drag and drop a thumbnail from the Thumbnail Window, double-click on a thumbnail in the Thumbnail Window or select an image and choose Images > Edit Mask menu item.

The mask is displayed semi-transparently over the top of the colour image. The masked region defines the parts of this view that are definitely not part of the object (in other words the background). It is important not to over-mask the object, but it does not necessarily matter if you do not mask all of the background.

You can change how the mask is displayed from the Mask Tools > Display Mask menu. You can change the colour used to display the mask so that it shows up well against your images from The 3DSOM Pro Settings Window.

With the Zoom in button or Zoom out button selected, you can zoom into or out from the image by a single click of the left mouse button. Alternatively, you can select the zoom value from the drop down menu or the Mask Tools > Zoom to... menu.

When you are zoomed into the image, you can scroll around freely in two dimensions by selecting the Pan image button. Alternatively, you can use the scrollbars around the window to scroll vertically or horizontally.

TIP:	As a shortcut, holding down the SPACE key temporarily switches to the Pan image tool and releasing it returns you to your previous tool.

The Zoom to fit button changes the magnification and pans so that the whole unmasked region fits within the window.

3.4.2. Undoing Mask Changes

A short undo history is kept for all changes to the masks for each image. You can only undo changes to the image that is currently displayed in the Edit Masks Window, but the history is kept separately for each image, even while you have a different image displayed in the Edit Masks Window. Even changes made from the Mask Wizard can be undone. This can be particularly useful for seeing whether automatic masking with different parameters has made an improvement or not. Note that this undo information is not saved in the project file.

Use the Undo model or mask change button in the main toolbar to return to the previous mask for the image and Redo model or mask change button to re-apply the change.

3.4.3. Automatic Masking Tools

The automatic masking tools in the Edit Masks Window enable you to perform automatic masking interactively, allowing you to adjust the parameters to improve the mask and to apply the tools to selected regions of the image only. See the Fine tuning the auto-masking and Manual masking with the shrink-wrap tool tutorials for a description of how to use these tools effectively.

The Regenerate mask button sets up interactive masking for the current image. After this has been run, the threshold for the image can be varied interactively by adjusting the slider that appears in the toolbar below this button. Changing the slider also adjusts the threshold that will be used for masking further images automatically through the Mask Wizard.

The Shrink-wrap Mask button sets up an alternative interactive masking technique. Unlike Regenerate mask this technique uses the current mask as a starting point and then shrinks the unmasked region down. Again, moving the slider adjusts how far the unmasked regions are shrunk.

The Unmask image button is a quick way of deleting the entire mask for the image.

The Clean Mask button is only available once some geometry has been generated. Clicking on it uses the shape of the current model to clean up the mask so that all parts of the image that fall outside the model when viewed from this viewpoint are masked out. It can also be used for generating an initial mask for new images as utilised in Advanced Masking for a large set of images.

The "Shadows" option toggles whether colour normalisation is used by the automatic masking algorithms to attempt to compensate for shadows on the backdrop.

If the "Holes" option is selected, the automatic masking tools may create isolated patches of mask. If your object is made of a single structure without any holes, it is worth keeping this option deselected to avoid holes being made in the mask.

3.4.4. Manual Masking Tools

The manual masking tools allow you to modify the mask by hand. We recommend that you avoid doing this by using the automatic masking tools wherever possible. The Creating or editing masks in an external application tutorial explains how to use your favourite third party image editing software to perform masking.

Each tool can be used either with the Paint mask button selected to add to the masked region or with the Unpaint mask button selected to add to the unmasked region.

TIP:	While using any of the manual masking tools, you can temporarily switch between Paint mask and Unpaint mask by pressing and holding the Ctrl key.

There are two brush tools for freehand painting. Click on either the Round Brush button or the Square Brush button to select them. The size of the brush is adjusted using the slider above these tools. The cursor changes to show the shape and size of the brush (except when zoomed right in).

TIP:	You can also use the < and > keys to change the brush size in large steps or the , and . keys to change the brush size in single pixel steps.

Note: If you are zoomed in, as you paint near the edge of the window, the window will automatically scroll to keep the brush visible. If you don't like this behaviour or it is too slow on your graphics card, you can switch it off by deselecting the "Automatically scroll canvas when painting" option from the 3DSOM Pro Settings Window.

The Fill mask button selects a simple fill tool. Clicking on a region of unmasked pixels will mask them (or vice versa depending on the current painting mode).

The Fill Polygon button switches to a polygon drawing mode. Click once on each vertex of the polygon you want to fill in turn and then double-click on the last vertex to perform the fill. As you click each vertex, you can drag the vertex around to adjust the position of the line before releasing the mouse button at the chosen position. To abort without performing the polygon fill, simply select a different tool .