4.3. Tutorial: Manual masking with the shrink-wrap tool

Problem

Sometimes it is difficult to set-up a suitable backdrop and stand to allow automatic masking to work well (for example the stand may need to be a different colour to the backdrop). However completely manual masking can be tedious and error-prone.

Solution

3DSOM Pro provides a semi-automatic tool to make manual masking easier. Simply sketch a very rough outline around the object and the mask can be "shrink-wrapped" onto the object for quick and accurate masking.

Starting Point

Load one or more photographs of the object (including calibration mat) for masking. Select one of the images by double-clicking the desired thumbnail.

Step 1

Remove any existing mask using the ID_UNMASK_IMAGE.jpgUnmask image button from the Edit Masks toolbar.

Step 2

Select the ID_PAINT_MASK.jpgPaint mask button to paint in the mask colour and select a round brush using the ID_PAINT_ROUND_BRUSH.jpgRound Brush button. Adjust the brush slider to select a thick brush (around 20 pixels). Now paint a very rough outline around the object. Make sure you keep the mask colour completely outside the object.

TIP:

The outline can be very rough but make sure you don't touch the object you are trying to mask. If there are holes in the object shape you can also paint inside these areas to help the masking process.
Step 3

Hit the ID_SHRINKWRAP.jpgShrink-wrap Mask button and drag the masking slider to interactively shrink-wrap the mask. Move the slider to the right to create more mask colour and to the left to create less mask colour.

Step 4

For finer control you can modify the shrink-wrap threshold in a rectangular region of the image. Simply click the ID_PAINT_SELECTREGION.jpgregion select button. Then select the desired image region by dragging with the left mouse button. Now drag the masking slider to interactively set the threshold for the selected region only.

Step 5

Select or deselect the "Holes" checkbox to allow or disallow holes in the object. Clicking this button will instantly update the mask. The colour normalisation setting has no effect when shrink-wrapping.

Figure 4.3.1. Fine-tuning a region with holes selected
Figure 4.3.2. Fine-tuning a region without holes selected
TIP:

At any stage, you can re-run the shrink-wrapping using the current mask as a starting point. This can be helpful when fine-tuning the mask in a selected region.

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