Tutorial: Adding synthetic silhouettes

4.6. Tutorial: Adding synthetic silhouettes

Problem

Sometimes, after taking the photographs and starting to build the model, you may realise that to capture the geometry better you needed to take an image from a different angle.

Solution

If you have not moved the object you can simply take another photograph and add it to the project using the Images > Add Images... menu item. If you have moved the object, you would need to align the new image as described in the Adding texture underneath an object tutorial.

If you no longer have access to the object or do not want to take any more photographs of it, you can create a synthetic view as described below, edit the silhouette and then re-generate the surface using this silhouette.

TIP:	See also the Optimising the surface geometry tutorial for other automatic ways of improving the surface which might be just as effective.

Starting Point

Before you can create a synthetic view, you will need to have a project with a wireframe surface generated. It is often easier if you have also generated a texture map.

Step 1

In the View Model Window, rotate and position the model until you are looking at it from an angle that shows as much of the erroneous geometry on the silhouette of the object as possible.

Figure 4.6.1. The model rotated showing as much of the unwanted geometry on the arm (highlighted) as possible.

If you cannot find a single angle from which all of the geometry is visible, you may need to use this procedure to create multiple silhouettes.

Step 2

Click the Create silhouette button. If you have a texture map generated, you will be prompted whether to save a virtual image of the model to help you with your mask editing. This is generally a good idea, since it is otherwise hard to edit the mask precisely. Choose a folder and filename to save the synthetic image in.

The new synthetic image will appear in the Thumbnail Window with an initial mask generated from the current geometry. Synthetic images are not used for texturing and are indicated as type "silhouette".

Note: Make sure that the whole object is visible in the new image, otherwise your geometry may get clipped — if necessary, delete the new image, zoom out a bit and create it again.

Step 3

Load the new mask into the Edit Masks Window by double clicking on its thumbnail. Edit the mask so that the geometry is corrected.

Figure 4.6.2. The synthetic image and mask ready for editing.

Figure 4.6.3. The mask after editing to improve the shape of the arm.

Step 4

Re-generate the surface by clicking Generate surface... button and following the normal procedure as described in Building the wireframe model.

Figure 4.6.4. The model after being regenerated showing the corrected geometry for the arm.