The natural way to handle such an object is to take two sets of photographs, turning the object over in between. In normal operation, 3DSOM Pro assumes that the object does not move relative to the mat, but this is not the case, so the second set of images has to be aligned with the first set.
The Align Wizard is used to help the process of merging the two sets of images together to form a single project. 3DSOM Pro needs to determine how the object has moved between taking the two sets of photographs.
This can be automated by building a partial model from one set of photos and letting the software compute how the second set is oriented relative to the first set. Any number of additional scans can be merged in this manner.
Make sure your images for the two scans are stored in separate folders as this will help keep track of which images were taken for each scan (and avoid file naming conflicts). It can help to store the second scan in a subfolder e.g. named "side_shots").
For the example shots in this tutorial, we have captured separate calibration images, normal images and stripe images of a fossil (vertebra) using two cameras, with the object sitting flat. We then rotated the object onto it's side and took another complete sequence of the normal and stripe images - the cameras and turntable remained fixed so we didn't need to taken a second set of calibration shots.
Create a new project and load the in the images from the first folder. In our example we have calibration, normal and stripe images for two cameras with our fossil object sitting flat (thumbnails below).
Add the images from the 2nd scan (which should be in a separate folder) using the menu item from the menu. In our example the second scan was taken by rotating the object on it's side and capturing another sequence of normal and stripes shots from both cameras.
Hit the button and select the desired quality and optionally texture settings.
Generate a quick wireframe mesh using the
Figure 5.3.3. Simple wireframe from first scan - the calibration target(s) is displayed showing the underside has not been
If your second scan also contains calibration shots then you should delete all the existing calibration shots from the current project by selecting the thumbnails and using the menu item from the menu.
Add the images from the 2nd scan using the menu item from the menu. In our example the second scan was taken by rotating the object on it's side and capturing another sequence of normal and stripes shots from both cameras.
If there were no masks, click the button to mask the newly added shots (they should already be selected).
Select the second set of images (it doesn't matter if they are currently marked as rejected) and choose the Align Wizard will be shown. All the other images now appear locked (greyed out) in the Thumbnail Window. menu item. Make sure all the images in the second scan were selected including the normal and stripe shots for all cameras used. The
Choose button to move onto the next page.
At this point, look at View Model Window — it displays the current model semi-transparently over one of the selected set of images. You can rotate and move the model as normal. Use the button (and the button) on the View Model toolbar if you want to move back to where you were previously.
You can use either the "playback" buttons ( button, button, button and button) in the wizard to move to a different image. When you change to a different image, the model will be rotated so that it remains in a consistent orientation relative to the second set of images.
|Figure 5.3.4. The same orientation of the model seen from two different cameras against their respective backdrop images.|
As long as there are enough images in the second set and they have been properly masked, 3DSOM Pro will be able to align the object automatically. This is a great advantage, since it is tedious to get the alignment right by hand - it can look good from one image, but from a different image can be far out of alignment. Use the button to get 3DSOM Pro to pick an initial alignment.
Switch between (F5), and (F6) or (F7) display modes to help show the model up against the photograph.
Sometimes, particularly with fairly symmetric objects, 3DSOM Pro will be unable to tell which way round the object is — each time you click the button it will cycle through a series of possible alignments.
Hit the button to begin optimising the alignment. During the optimisation stage, 3DSOM Pro attempts to make minor changes to the orientation and position of the object whilst checking that it matches the silhouettes of the chosen images. You will see the object "vibrate" during this process and you can check the alignment against different images as before.
|< Previous topic|
(File Naming Convention)
|Next topic >
(Advanced Masking for a large set of images)