The neuron cell's output can be oriented in 6 different ways in the 3D space. A dendrite cell also has five inputs and one output, to collect signals from other cells. The incoming signals are passed to the output with an 5-bit XOR function. An axon cell is the opposite of a dendrite. It has 1 input and 5 outputs, and distributes signals to its neighbors.
Blank cells perform no function in an evolved neural network.
They are used to grow new sets of dendritic and axonic trees during the evolution mode. Before the growth begins, the module space consists of blank cells. Each cell is seeded with a 6-bit chromosome. The chromosome will guide the local direction of the dendritic and axonic tree growth. Six bits serve as a mask to encode different growth instructions, such as grow straight, turn left, split into three branches, block growth, T- split up and down etc.