ddmyx/objects/oRippleExpand/Draw_64.gml

draw_set_color(c_black);
draw_set_alpha(1.0);

var _segments = 64;
draw_primitive_begin(pr_trianglestrip);

for(var i = 0; i <= _segments; i++)
{
    var _angle = i * (360 / _segments);
    var _dx = dcos(_angle);
    var _dy = dsin(_angle);
    draw_vertex(ui_x + _dx * r_out, ui_y - _dy * r_out);
    draw_vertex(ui_x + _dx * max(0, r_in), ui_y - _dy * max(0, r_in));
}

draw_primitive_end();