<!-- This file is to illustrate the use of the element ray and constraint ray_from_point_and_vector.
     It still has not been run on any DGS, so it may contain bugs. 
	 
	 r is the ray starting at A following vector v; v is the vector from P to Q
	 -->
<construction xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../xml/intergeo.xsd">
	<elements>
		<point id="A">
			<homogeneous_coordinates>
				<double>-1.0</double>
				<double>1.0</double>
				<double>1.0</double>
			</homogeneous_coordinates>
		</point>
		<point id="P">
			<homogeneous_coordinates>
				<double>1.0</double>
				<double>0.0</double>
				<double>1.0</double>
			</homogeneous_coordinates>
		</point>
		<point id="Q">
			<homogeneous_coordinates>
				<double>2.0</double>
				<double>1.0</double>
				<double>1.0</double>
			</homogeneous_coordinates>
		</point>
		<vector id="v">
			<homogeneous_coordinates>
				<double>1.0</double>
				<double>1.0</double>
				<double>1.0</double>
			</homogeneous_coordinates>
		</vector>
		<ray id="r">
			<homogeneous_coordinates>
				<double>-1.0</double>
				<double>1.0</double>
				<double>1.0</double>
			</homogeneous_coordinates>
			<direction>
				<double>1.0</double>
				<double>1.0</double>
				<double>1.0</double>
			</direction>
		</ray>
	</elements>
	<constraints>
		<free_point>
			<point out="true">A</point>
		</free_point>
		<free_point>
			<point out="true">P</point>
		</free_point>
		<free_point>
			<point out="true">Q</point>
		</free_point>
		<vector_from_point_to_point>
			<vector out="true">v</vector>
			<point>P</point>
			<point>Q</point>
		</vector_from_point_to_point>
		<ray_from_point_and_vector>
			<ray out="true">r</ray>
			<point>A</point>
			<vector>v</vector>
		</ray_from_point_and_vector>
	</constraints>
</construction>
