Block Families - Terasology/TutorialAssetSystem GitHub Wiki

A block family is a group of multiple variations of one block, such as the same base block but in different shapes. The main purpose of a block family is to allow the user to collect multiple of those block variants for a given family that'll then join into the same single generic stack again.

For example a wall-torch and a ground-torch will both be collected to the same stack of torches. However, there is a separate block for the wall torch (in fact, there are 4 of them, one for each rotation) and a separate block for the ground torch. Likewise fence blocks will adjust their shape to connect to neighbors, but all count as a single generic fence block.

A block family for a block is defined in the .block file via the family section(see Block Definition).

When a family is generated from a block, it will create multiple instances for the block, all referenced by different BlockUri.

You may want to have a look at the documentation of org.terasology.world.block.BlockUri.