void displayTrails() {
		strokeWeight(2);							// no stroke for the shape.
		for (Agent a : agt.getAgents()) {
			String agtType = a.getType();
			ArrayList<Vec3D> trail = a.getTrail();
			if (agtType.equals("a")) {
				stroke(0, 0, 200);					// fill color, a dark blue.
				for (Vec3D v : trail) {
					point(v.x, v.y, v.z);			// an ellipse with center in the loc vector's coordinates, and 2 units wide and 2 units tall.
				}
			}
			if (agtType.equals("b")) {
				stroke(0, 200, 0);					// fill color, a dark green.
				for (Vec3D v : trail) {
					point(v.x, v.y, v.z);			// an ellipse with center in the loc vector's coordinates, and 2 units wide and 2 units tall.
				}
			}
			if (agtType.equals("c")) {
				stroke(200, 0, 0);					// fill color, a dark red.
				for (Vec3D v : trail) {
					point(v.x, v.y, v.z);			// an ellipse with center in the loc vector's coordinates, and 2 units wide and 2 units tall.
				}
			}
		}
	}