Tightening up a photo mosaic geometry

 

Debugging a users photo mosaic issue in Studio Artist V5.5.  So the trick for this kind of thing if you care about having an absolutely rigid geometry is to use the Selection Override option for the region as Brush Mode Generator as seen below.

And of course you need to make sure you are using the Each Region as Mask option for the Region Mask Opt in the Path Shape control panel as seen below.

When you set it up this way, then each painted region is directly generated from the set of Path Start Regionize (as defined in the Path Start control panel) regions.

The normal paint synth pathways will take the individual regions, try to fit some kind of path to or in them based on the Path Shape control panel settings, then convert that path back to a raster region again for the actual Region Fill as Brush pen mode paint fill.  Remember, Region Fill as Brush pen mode subverts the normal 'paint a series of paint nibs along the path' approach to painting and paints the entire path as one temporary virtual brush nib.

And the paths generated by the Path Shape control panel settings might try to match the outline of the region, or fill it with hatching or other fill patterns, and of course could be modulated or inhibited by a million different possible settings in the paint synthesizer.  This can introduce some subtle (or not so subtle) changes to the rigid geometry of this particular sub-nested tiling setup.

Using the Selection Override option for the generating the virtual brush nib for the painting region avoids any issues with the 'region to path back to region' process.  So you absolutely maintain the original rigid geometry for the virtual brush nib fill.