public void Draw_Line3D(R3DVECTOR start, R3DVECTOR end, R4DVECTOR color)
{
VertexPositionColor[] v = new VertexPositionColor[3];
v[0] = new VertexPositionColor(start.vector, new Color(color.vector));
v[1] = new VertexPositionColor(end.vector, new Color(color.vector));
_instance._basicEffect.View = REngine.Instance._camera.viewMatrix;
_instance._basicEffect.Projection = REngine.Instance._camera.projMatrix;
_instance._basicEffect.World = Matrix.Identity;
_instance._basicEffect.VertexColorEnabled = true;
_instance._basicEffect.CurrentTechnique.Passes[0].Apply();
// Draw the triangle.
REngine.Instance._graphics.GraphicsDevice.DrawUserPrimitives(PrimitiveType.LineList,
v, 0, 1);
}