Not really,what you do is you plot the outline of the points you want:
Square example:
PHP Code:
temp.square={20,20,40,20,40,40,20,40};
showpoly (300, temp.square);
And this is how I drew it in order of verticies
Another example would be drawing a circle:
PHP Code:
temp.radius=4;
for (temp.i=0;temp.i<(pi*2);temp.i++)temp.circle.add((cos(temp.i)*temp.radius+30),(sin(temp.i)*temp.radius+30));
showpoly (300, temp.circle);
So basically summing up, you draw the outline and the showpoly will fill in the middle. And basically what I've done here in both examples is define an array outside the showpoly statement rather then within it. Hope this helped.