5.1. Tutorial: Advanced Masking for a large set of images

Problem

Sometimes the photographs taken will not be suitable for auto-masking — e.g.

If there are a large number of images, accurate manual masking could take a long time.

Solution

3DSOM Pro provides a number of semi-automatic tools for improving the workflow to allow more rapid masking of multiple images.

Starting Point

Start with a project consisting of a large number of challenging images. Remove the existing inaccurate masks using the Masking > Unmask Images menu item.

Step 1

Firstly we will put the thumbnails in a special prioritised order. View the thumbnail details by clicking the ID_VIEW_REPORT.jpgView image details button. Now click the "Order" tab so that the thumbnails are displayed in increasing order values. This will ensure that the first few images are from widely differing viewpoints.

Step 2

Double-click the first thumbnail. Now create a mask using the appropriate masking tools (see Manual masking with the shrink-wrap tool).

Figure 5.1.1. Masking the first thumbnail in the ordered list
Step 3

Repeat the process for the first 3 or 4 images in the ordered list.

Figure 5.1.2. Masks created for the next three images
Step 4

Now we generate a rough 3D model using these few images. Hit the ID_MAKE_SURFACE.jpgGenerate surface... button to launch the Surface Wizard. Select the "Generate wireframe" option and hit Next > button. Use the default parameters and hit Next > button to create an initial 3D model. Now close the wizard.

Figure 5.1.3. Rough wireframe model
TIP:

Don't optimise the surface at this stage - we want a rough overestimate of the space in which the object must lie.
Step 5

Select the next un-masked thumbnail by double-clicking.

Step 6

We can now project the 3D model into the selected image to get an initial estimate for the mask. Click the ID_CLEANMASK.jpgClean Mask button.

If necessary, unpaint any areas of the object that have been incorrectly shown as mask coloured.

Figure 5.1.4. Initial estimate obtained from model
Step 7

Now shrink-wrap the rough estimate onto the object. Click the ID_SHRINKWRAP.jpgShrink-wrap Mask button and drag the masking slider until the desired mask is obtained.

Figure 5.1.5. Mask shrink-wrapped from the initial estimate
TIP:

For improved workflow the last two steps can be combined. Clicking the ID_SHRINKWRAP.jpgShrink-wrap Mask button for an un-masked image will automatically perform a clean mask operation followed by shrink-wrapping.
Step 8

You can fine-tune the shrink-wrapping (see Manual masking with the shrink-wrap tool) and manual edit the result with the brush and other tools.

Step 9

Repeat for the remaining un-masked images.

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