The brain in Creatures is a very complex thing built of about 10 lobes, maybe 900 neurons and many thousands of dendrites. The brain works with the creature's biochemistry in order to keep itself alive.
A lobe is a part of the brain that is dedicated to a certain function. Each lobe has an x, y, width and height coordinate, giving it a unique position in the grid of the brain.
A neuron is a place where you can store a number value. Most neurons lose the saved value over time, but some do this faster than others.
Neurons live in lobes, and are connected to other neurons via dendrites.
Dendrites are the connections between different neurons. Dendrites work unidirectionally (one-way), so the value of neuron 1 may influence the value of neuron 2, but not vice versa. Dendrites may have different behaviours and some just transfer the value of one neuron to another one, while others may negate the value or do even more complex work. See also concept lobe.
Creature brains use a neuronal processing system called State Value Rules, commonly shortened to SVRules.
These were fairly simple in Creatures 1 and Creatures 2, essentially designed to let you perform simple manipulations upon Creature variables (ie, biochemistry and brain values), with the possibility of adding conditions based upon these variables.
In Creatures Evolution Engine games such as Creatures 3, each neuron and dendrite is a fully functional register machine. That means that you have several registers (places where you can store something) and one special working register. The most important commands on a register machine are LOAD, which loads a value into the working register and STORE, which stores a value from it into one of the other registers.
Operations like ADD always use the value of the working register. Look at the following example, which adds the value from register 1 to the one of register 0 and stores the new value in register 2:
- LOAD 0
- ADD 1
- STORE 2
The SVRules system adds some extensions to the usual register machine, like access to the Creature's chemical system or to its reception.
A good place to learn more about the brain is The Creatures Developer Resource
A note from the programmer
This SVRule system was designed to deal with an interesting problem: How could I specify arbitrary behaviours for my neurons in a way that evolution could freely change, without it generating endless syntax errors in the process? For instance, imagine that a mutation were to occur in a line of conventional C++ code, such as "for (i=0; i<num; i++)". Almost every possible mutation would render the code unreadable (e.g. "fxr (i-0; ibnum; i4+)") and the chances of a useful (or even viable) mutation would be extremely low. At worst the whole simulation would crash.
To solve this problem I designed the SVRule system in such a way that EVERY statement you can write in it is legal and meaningful, even if it is not biologically useful. If a token was originally the operand for a command, for example, and the command later mutated to one that didn't require operands, the token would now be interpreted instead as a new command or a variable. The details of this aren't very important, but I guess it's an interesting example of the ways in which biology differs from computer programming. Biology tends to have this sort of robustness built into the design.
—Digitalgod 12:39, 4 Apr 2005 (EDT)
In the games after C2, one way in which creatures can die is by the lifeforce of the brain organ - which contains only the brain lobes - becoming too low. This happens when the organ receives sufficient damage which, due to the lack of other biochemistry inside the organ, only happens when a creature has insufficient ATP. The gene which governs this organ has a similar structure to other organ genes.
Tracts were introduced in the Creatures Evolution Engine as a new object for managing dendrites. Each tract defines a set of dendrites connecting between two lobes. This allowed brains to be more complex compared to Creatures 1 and Creatures 2, in which each lobe could only have up to two types of dendrites connecting to it.
|C1 opcode||C2 opcode||name||description|
|0||0||<end>||Marks the end of an SVRule. Any opcodes appearing after this marker are ignored.|
|1||1||0||The integer number zero.|
|2||2||1||The integer number one.|
|3||3||64||The integer number sixty-four.|
|4||4||255||The integer number two hundred fifty-five.|
|5||5||chem 0||Current amount of chemical 0 in the brain lobe. This chemical can be changed with a biochemical receptor.|
|6||6||chem 1||See above.|
|7||7||chem 2||See above.|
|8||8||chem 3||See above.|
|9||9||state||Current value of the state of the cell.|
|10||10||output||Current output value of the cell.|
|11||11||thres||Current threshold of the cell.|
|12||12||type 0||The sum of type 0 dendrites. The individual value of each dendrite for this type is summed and returned. The individual value of a dendrite appears to be calculated as: |
|13||13||type 1||See above.|
|14||14||anded 0||If all type 0 dendrites are firing then this will be the value of the sum of these dendrites. If any of the type 0 dendrites are not firing then this value will be 0.|
|15||15||anded 1||See above.|
|16||16||input||Current dendrite input signal.|
|17||17||conduct||Not hooked up in Creatures 1. Unknown in Creatures 2.|
|18||18||suscept||Current susceptibility to reinforcement. This is the value calculated by the 'susceptibility' state variable rule on the dendrite dynamics pages of the genetics kit. This opcode should only appear in the svrules associated with dendrites (otherwise there is no way to determine what dendrite it is pulling the data from).|
|19||19||STW||The value of the short term weight setting for the given dendrite. This opcode should only appear in the svrules associated with dendrites (otherwise there is no way to determine what dendrite it is pulling the data from). The short term weight for a dendrite appears to be calulated using the following formula with a relaxation decay applied to it: |
|20||20||LTW||The value of the long term weight setting for the given dendrite. The long term weight acts as a rest state for short term weight. STW and LTW reduce towards each other with LTW moving slower than STW. This opcode should only appear in the svrules associated with dendrites (otherwise there is no way to determine what dendrite it is pulling the data from).|
|21||21||strength||Current value of dendrite strength. This opcode should only appear in the svrules associated with dendrites (otherwise there is no way to determine what dendrite it is pulling the data from).|
|22||32||The integer number thirty-two.|
|23||128||The integer number one hundred twenty-eight.|
|25||chem 4||Current amount of chemical 0 in the brain lobe. This chemical can be changed with a biochemical receptor.|
|26||chem 5||See above.|
|27||leak in||This appears to be related to the value of the 'back propagation' state variable rule. If any other lobe has this current lobe as a 'source lobe' in its dendrite settings then the value of 'leak in' for the current lobe is the value of the 'back propagation' svrule from the destination dendrite. This can be used to feed data back to a source lobe from destination lobes.|
|28||leak out||This appears to be related to the value of the 'forward propagation' state variable rule. If the current dendrite has a 'forward propagation' svrule then the 'leak out' opcode is the value of that 'forward propagation' calculation.|
|29||curr src leak in||The neuron's current dendrite's source neuron leak in charge.|
|22||30||TRUE||If the previous opcode evaluates to TRUE (ie. not zero) then execute the remaining opcodes otherwise the value of state is zero and the SVRule completes.|
|23||31||PLUS||Adds the value of the following opcode to the value of the previous opcode.|
|24||32||MINUS||Subtracts the value of the following opcode from the value of the previous opcode. For example |
|25||33||TIMES||Takes the left hand opcode multiplied by the right hand opcode and divides this by 256. The result of this calculation is the value of this opcode. For example: |
|26||34||INCR||Returns the value of the previous opcode incremented by one.|
|27||35||DECR||Returns the value of the previous opcode decremented by one.|
|36||FALSE||If the previous opcode evaluates to FALSE (ie. zero) then execute the remaining opcodes otherwise the value of state is zero and the SVRule completes.|
|37||multiply||Multiplies the value of the following opcode with the value of the previous opcode.|
|38||average||Averages the value of the following opcode with the value of the previous opcode.|
|40||random||This opcode takes two arguments. It returns a random number between the first argument and the second argument. It also sets rnd const.|
|List of State Variable Rules (Genetics Kit)|
|set tend rate|
|load negation of|
|load abs of|
|get distance to|
|register as spare|
|bound in [0,1]|
|bound in [-1,1]|
|add and store in|
|tend to, store in|
|Input Gain Hi Lo|
|Winner Takes All|
|ShortTerm Relax Rate|
|LongTerm Relax Rate|
|store abs in|
|stop if zero|
|stop if nonzero|
|if zero goto|
|if nonzero goto|
|div by, add to neuron input|
|mult by, add to neuron input|
|stop if <|
|stop if >|
|stop if <=|
|stop if >=|
|Use Reward With|
|Use Punish With|
|Preserve Neuron SV|
|Restore Neuron SV|
|Preserve Spare Neuron Var|
|Restore Spare Neuron Var|
|if negative goto|
|if positive goto|
- Creatures: Artificial Life Autonomous Software Agents for Home Entertainment by Steve Grand et al.
- I Am Ron's Brain
- The AI of Creatures by Alan Zucconi
- Creatures 1 Brain spreadsheet by Alan Zucconi
- An online brain viewer tool for C1 export files
- State Variable Rules at The Creatures Developer Resource
- Creatures 3 SV Rules at Ratboy's Creatures3 Stuff
- C2e Brains at the CCDevNet wiki