7. Agent Aspect

In this seventh step, we will focus on the display and more specifically the aspects of the agents: how they are represented. It can be a simple shape (circle, square, etc.), an icon, a polygon (see later GIS support).

Formulation

• Definition of two new aspects for the prey and predator agents:
  • A icon
  • A square with information about the agent energy
• Use of the icon aspect as default aspect for the prey and predator agents.

Model Definition

parent species

We add a new variable of type image_file (a particular kind of file) called my_icon to the generic_species. We define as well two new aspects:

• icon: draw the image given by the variable my_icon,
• info: draw a square of side size size and color color and draw as a text the energy of the agent (with a precision of 2 digits).

species generic_species {
    ...
    image_file my_icon;
    ...
    aspect base {
        draw circle(size) color: color ;
    }
    aspect icon {
        draw my_icon size: 2 * size ;
    }
    aspect info {
        draw square(size) color: color ;
        draw string(energy with_precision 2) size: 3 color: #black ;
    }
}

prey species

We specialize the prey species from the generic_species species as follows:

• definition of the initial value of the agent variables:

species prey parent: generic_species {
    ...  
    image_file my_icon <- image_file("../includes/data/predator_prey_sheep.png") ;
    ...
}

The image file is here: .

You have to copy it in your project folder: includes/data/.

predator species

As done for the prey species, we specialize the predator species from the generic_species species:

• definition of the initial value of the agent variables:

species predator parent: generic_species {
    ...
    image_file my_icon <- image_file("../includes/data/predator_prey_wolf.png") ;
    ...
}

The image file is here: .

You have to copy it in your project folder: includes/data/.

display

We change the default aspect of the prey and predator agents to icon aspect.

output {
    display main_display {
        grid vegetation_cell lines: #black ;
        species prey aspect: icon ;
        species predator aspect: icon ;
    }
}

We define a new display called info_display that displays the prey and predator agents with the info aspect.

output {
    display info_display {
	grid vegetation_cell lines: #black ;
        species prey aspect: info;
        species predator aspect: info;
    }
}

Complete Model

model prey_predator

global {
    int nb_preys_init <- 200;
    int nb_predators_init <- 20;
    float prey_max_energy <- 1.0;
    float prey_max_transfert <- 0.1;
    float prey_energy_consum <- 0.05;
    float predator_max_energy <- 1.0;
    float predator_energy_transfert <- 0.5;
    float predator_energy_consum <- 0.02;
    float prey_proba_reproduce <- 0.01;
    int prey_nb_max_offsprings <- 5;
    float prey_energy_reproduce <- 0.5;
    float predator_proba_reproduce <- 0.01;
    int predator_nb_max_offsprings <- 3;
    float predator_energy_reproduce <- 0.5;
    int nb_preys -> {length(prey)};
    int nb_predators -> {length(predator)};

    init {
        create prey number: nb_preys_init;
        create predator number: nb_predators_init;
    }
}

species generic_species {
    float size <- 1.0;
    rgb color;
    float max_energy;
    float max_transfert;
    float energy_consum;
    float proba_reproduce;
    int nb_max_offsprings;
    float energy_reproduce;
    image_file my_icon;
    vegetation_cell my_cell <- one_of(vegetation_cell);
    float energy <- rnd(max_energy) update: energy - energy_consum max: max_energy;

    init {
        location <- my_cell.location;
    }

    reflex basic_move {
        my_cell <- one_of(my_cell.neighbors2);
        location <- my_cell.location;
    }

    reflex eat {
        energy <- energy + energy_from_eat();        
    }

    reflex die when: energy <= 0 {
        do die;
    }

    reflex reproduce when: (energy >= energy_reproduce) and (flip(proba_reproduce)) {
        int nb_offsprings <- rnd(1, nb_max_offsprings);
        create species(self) number: nb_offsprings {
            my_cell <- myself.my_cell;
            location <- my_cell.location;
            energy <- myself.energy / nb_offsprings;
        }

        energy <- energy / nb_offsprings;
    }

    float energy_from_eat {
        return 0.0;
    }

    aspect base {
        draw circle(size) color: color;
    }

    aspect icon {
        draw my_icon size: 2 * size;
    }

    aspect info {
        draw square(size) color: color;
        draw string(energy with_precision 2) size: 3 color: #black;
    }
}

species prey parent: generic_species {
    rgb color <- #blue;
    float max_energy <- prey_max_energy;
    float max_transfert <- prey_max_transfert;
    float energy_consum <- prey_energy_consum;
    float proba_reproduce <- prey_proba_reproduce;
    int nb_max_offsprings <- prey_nb_max_offsprings;
    float energy_reproduce <- prey_energy_reproduce;
    image_file my_icon <- image_file("../includes/data/sheep.png");

    float energy_from_eat {
        float energy_transfert <- 0.0;
        if(my_cell.food > 0) {
            energy_transfert <- min([max_transfert, my_cell.food]);
            my_cell.food <- my_cell.food - energy_transfert;
        }             
        return energy_transfert;
    }
}

species predator parent: generic_species {
    rgb color <- #red;
    float max_energy <- predator_max_energy;
    float energy_transfert <- predator_energy_transfert;
    float energy_consum <- predator_energy_consum;
    float proba_reproduce <- predator_proba_reproduce;
    int nb_max_offsprings <- predator_nb_max_offsprings;
    float energy_reproduce <- predator_energy_reproduce;
    image_file my_icon <- image_file("../includes/data/wolf.png");

    float energy_from_eat {
        list<prey> reachable_preys <- prey inside (my_cell);
        if(! empty(reachable_preys)) {
            ask one_of (reachable_preys) {
                do die;
            }
            return energy_transfert;
        }
        return 0.0;
    }
}

grid vegetation_cell width: 50 height: 50 neighbors: 4 {
    float max_food <- 1.0;
    float food_prod <- rnd(0.01);
    float food <- rnd(1.0) max: max_food update: food + food_prod;
    rgb color <- rgb(int(255 * (1 - food)), 255, int(255 * (1 - food))) update: rgb(int(255 * (1 - food)), 255, int(255 * (1 - food)));
    list<vegetation_cell> neighbors2 <- (self neighbors_at 2);
}

experiment prey_predator type: gui {
    parameter "Initial number of preys: " var: nb_preys_init min: 0 max: 1000 category: "Prey";
    parameter "Prey max energy: " var: prey_max_energy category: "Prey";
    parameter "Prey max transfert: " var: prey_max_transfert category: "Prey";
    parameter "Prey energy consumption: " var: prey_energy_consum category: "Prey";
    parameter "Initial number of predators: " var: nb_predators_init min: 0 max: 200 category: "Predator";
    parameter "Predator max energy: " var: predator_max_energy category: "Predator";
    parameter "Predator energy transfert: " var: predator_energy_transfert category: "Predator";
    parameter "Predator energy consumption: " var: predator_energy_consum category: "Predator";
    parameter 'Prey probability reproduce: ' var: prey_proba_reproduce category: 'Prey';
    parameter 'Prey nb max offsprings: ' var: prey_nb_max_offsprings category: 'Prey';
    parameter 'Prey energy reproduce: ' var: prey_energy_reproduce category: 'Prey';
    parameter 'Predator probability reproduce: ' var: predator_proba_reproduce category: 'Predator';
    parameter 'Predator nb max offsprings: ' var: predator_nb_max_offsprings category: 'Predator';
    parameter 'Predator energy reproduce: ' var: predator_energy_reproduce category: 'Predator';

    output {
        display main_display {
            grid vegetation_cell lines: #black;
            species prey aspect: icon;
            species predator aspect: icon;
        }

        display info_display {
            grid vegetation_cell lines: #black;
            species prey aspect: info;
            species predator aspect: info;
        }

        monitor "Number of preys" value: nb_preys;
        monitor "Number of predators" value: nb_predators;
    }
}