Using the Stack Groups functionality the user can make the packer automatically align (stack) particular islands on top of each other before packing and then pack stacked islands together. Stacked islands will not be split during packing.
In order to use the Stack Groups functionality, enable the checkbox located in the Stack Groups subpanel header:
Stack groups are numbered (every group is identifiable by a number). In order to make the packer always stack given islands before packing, select these islands and assign the same stack group number to all of them. Note that islands belonging to a single group will be stacked only if they pass the similarity test i.e. using stack groups is logically equivalent to running the Align Similar (Stack) operator separately for every stack group and then running a packing operation on the results. The similarity test is driven by the standard similarity options from the Aligning Tools mode.
By default islands are not assigned to any stack group. Islands not assigned to a group are not processed by the stacking phase - they are packed during the packing phase together will all stacked islands in the usual manner.
Stack groups with the Align Similar operation
Stack groups can also be used when running the Align Similar (Stack) operation from the Aligning Tools mode.
The Correct Vertices similarity option during packing
Due to performance reasons the Correct Vertices similarity option is always ignored when packing with stack groups. The option is supported when using stack groups with the Align Similar (Stack) operation though. If you want to pack with stack groups and vertex correction enabled, perform the following procedure:
- assign islands to stack groups according to your needs,
- run the Align Similar (Stack) operation on the given islands with the Correct Vertices option enabled only once (in order to perform vertex correction),
- after vertex correction is done, you can now run subsequent packing operations with stack groups enabled and the Correct Vertices option ignored (it’s enough to perform vertex correction only once).