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).

• 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.

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 ;
    }
}

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/sheep.png") ;
    ...
}

The image file is here: .

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

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/wolf.png") ;
    ...
}

The image file is here: .

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

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;
    }
}

https://github.com/gama-platform/gama.old/blob/GAMA_1.9.2/msi.gama.models/models/Tutorials/Predator%20Prey/models/Model%2007.gaml