tutorial : documentation: Agency

TUTORIAL CONTENTS

2.0 Starting a Run

3.0 Interface Components
   3.1 Population
       3.1.1 Modify Individual
   3.2 Agent Control
       3.2.1 Bounding Box
       3.2.2 Shape Size
       3.2.3 Number of Shapes
       3.2.4 Local Bounding Box
       3.2.5 Overall Design Height
   3.3 ZoneType
   3.4 Genetic Engine
   3.5 Settings
   3.6 Miscellaneous
   3.7 About

4.0 Glossary

2.0 Starting a Run

1. Set up your NURBS curves.
   AgencyGP will operate on any set of NURBS curves without height components. That means you are free to load or create any curves you wish on any plane parallel to the base plane. These are the curves that will be manipulated and extruded in the GP. They may come from any sort of analysis or investigation.
   
2. Set up your shaders.
   AgencyGP will allow you to establish any number of types of zones with different desired spatial characteristcs. It will communicate what shape has been assigned to what zone by assigning a particular shader to it. So set up at least as many shaders as you are interested in having zone types and make them different enough in color or other characteristic to make them easily distinguishable. Give them names that you will be able to recognize them by: their color or their intended zone type are good choices.
   
3. Set the Shading mode to smooth.
   From the Shading menu at the top of your drawing window, select Smooth Shade All.
   
4. Position your scene.
   You will not be able to reposition or change the camera angle at all while AgencyGP is running, so it is essential that you set up your scene so that its contents can be easily evaluated during the run. The AgencyGP interface is somewhat large, so it is a good idea to make your scene somewhat small and position it to the bottom left of the screen. Rotate it so that your base plane is very oblique to the camera. That way tall extrusions will not be as likely to extend off the screen. Here is a picture of a scene properly positioned for a run of AgencyGP.
   
   
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5. Save your Maya scene.
   Please now save your scene. Nothing in this world is certain, and this is a great time to safeguard your work.
   
6. Select the curves you wish AgencyGP to operate on.
   Note that the more curves you select, the slower each generation will be to compute. There is a fairly low practical limit to how many curves it makes sense to select for a run. (No more than 5 for a quick run; no more than 20 for a slow run.)
   
7. Hit the button in Shelf 1 to invoke AgencyGP.
   If the button does not appear or the interface deos not appear after the button is pressed, consult troubleshooting.
   
8. The Population dialog page will show up. The only availavle option on it will be the "Initialize Population" button
   After setting up your zoneTypes, agents, and genetic engine the way you want them and saving your settings (see Interface), initialize your population, and begin evolving designs.
   

4.0 Glossary

Agent
An autonomous evaluative entity. It is deployed into a design and its evaluation of the design based on its editable criteria are accumulated with the opinions of other agents into the fitness measure of the design.

Bounding Box
A three-dimensional region outside of which a design is penalized for extending.

Command/Operation
A unit of our language. The commands are Opening, Translation, Scale, and Rotation.

Command List
Every shape in every design maintains an evolvable list of commands in our language which constitute part of its genotype. When the genotype is translated into the phenotype for evaluation by agents, the command list is run on the starting Maya curve, and the result is extruded into space.

Crossover
Analogous to biological genetic crossover: the replacement of a randomly selected segement of a shape's command list with a randomly selected segment of a command list from another shape.

Design
A design is the same as an individual. It is a member of a population, and consists of a genotype, a set of starting Maya curves, and a phenotype of shapes interpreted from the two.

Elite
Elites are individuals of the highest fitness that are transported directly into the new population without mutation.

Fitness
Fitness is the measure of quality that agents collectively give a design. Higher fitness means greater liklihood of having more offspring. So traits that the agents favor are selected for.

Generation
A generation is a name for a specific population of individuals. Generations are numbered sequentially.

Genetic Algorithms [GA]
The precursor to genetic programming, Genetic Algorithms use fixed-length, encoded genotypes, where Genetic Programming uses variable-size genotypes representing operations in an interpreted language.

Genetic Programming [GP]
A software methodology that seeks to evolve solutions to problems by generating populations of programs and then selectively breeding them.

Genotype
In the case of AgencyGP, a genotype consists of a set of Maya curves, a fixed-length list of parameters, and a variable-length list of commands.

Individual
See design.

Interruption, Intervention, and Resumption
The ability to stop and manually redirect the evolutionary process by manipulating the genotypes of individuals. AgencyGP allows this through the Modify Individual dialog.

Layer
A layer in a Maya scene is a method of grouping and showing or hiding objects. AgencyGP creates new layers to save intermediate results when requested.

Mutation
The random changing of a genotype in moving from one generation to the next. Mutation takes many forms in AgencyGP. They are all examined in the Genetic Engine dialog documentation.

NURBS curve
Non-uniform ration b-spline curve. This is the kind of geometry Maya creates that AgencyGP is capable of working with.

Phenotype
The physical expression of an individual's genotype. In the case of AgencyGP, the phenotype consists of one or many extruded shapes in a Maya scene.

Plug-in
A piece of software written in C++ that makes use of Maya's programming interface. It is a separate file that Maya loads and executes upon command.

Population
A population is a group of individuals ranked by fitness.

Pressure
Pressure is what good agents apply to the evolutionary process. Agents do not control what future generations will look like directly. Rather through selective pressure, they choose their favorite designs to reproduce. If a set of agents is too permissive, they will not be applying sufficient pressure to the system.

Shader
A shader is a Maya object that stores settings for rendering color, texture, and opacity of a surface.

Shape
A shape in an individual is one extruded element. Individuals may consist of many shapes. There may be more or fewer shapes in an interpreted phenotype than there were initial curves selected because of the variable effects of intersecting shapes.

Shape Mode
Shape mode determines how a shape behaves when it intersects with others. It may carve out of the other shape; it may be carved into itself; it may union with the other shape; they may intersect. There are 45 options, really three consecutive groups of 15.

Tournament Selection
Tournament size affects the way individuals are selected for breeding the new population. When creating a new population, the process is as follows: 1. Select [Tournament Size] individuals from the old population. 2. Take the fittest of these and make a copy of it. 3. Mutate the copy, cross its genes with another individual's or leave it be. 4. Place this copy into the new population. 5. Repeat 1-4 until the new population is filled.

Unfitness
AgencyGP ranks designs by unfitness. Therefore a low unfitness is better than a high one.

Variance
A measure of the amount of variation there is in a population. AgencyGP uses variance in fitness to estimate the genetic variance in a population, but that is a rather crude estimate. If agents are overly permissive, radically different individuals may be given the same low unfitness. It is, however, a convenient measure, and we use it.

Weight
The weight of a value is the emphasis a value is given when combining it with others. It only has meaning relative to the weights of the other values. 100 is neither a high nor a low weight. In the list 1, 1, 100 it is high. In the list 1000, 1000, 100, it is low.

Z-Height
This is a parameter of a shape which determines how tall its extrusion is. Remember that this may not represent the final height of the shape because all of the commands in the command list are executed on each shape before it is extruded. It may therefore be scaled up or down multiple times.

ZoneType
Before you use AgencyGP fully you must determine the parameters of your investigation. AgencyGP is best at dealing with problems in which desires of different types of spatial regions can be brought to apply pressure to one another.

Z-Widening
This is a parameter of a shape which determines the amount that a shape flares outward when extruded. A value higher than 1 flares outward, a value less than 1 contracts inward, and a value of 1 extrudes straight up.