%Coordinates of points spanning line
\pgfmathparse{0.5} \let\x\pgfmathresult;
\pgfmathparse{0.5} \let\y\pgfmathresult;

%Convex combinations parameters
\pgfmathparse{-0.2} \let\t\pgfmathresult;
\pgfmathparse{1-\t} \let\tt\pgfmathresult;
\pgfmathparse{\tt+0.2} \let\ttt\pgfmathresult;


\pgfmathparse{1.4} \let\s\pgfmathresult;
\pgfmathparse{-1.5} \let\ss\pgfmathresult;
\pgfmathparse{-1.8} \let\sss\pgfmathresult;

\coordinate (O) at (0,0);
\coordinate (Delta) at (3,0);


\coordinate (P1) at (\x,\y);
\coordinate (P2) at (-\x,-\y);

\coordinate (A) at (0,0);
\coordinate (B) at (-0.5,0.5);

\draw 
   ($(P1)!\t!(P2)$)
   --
   ($(P1)!\tt!(P2)$);

\draw ($(P1)!\ttt!(P2)$) node {$r$};


\coordinate (P1) at ($(P1)+(Delta)$);
\coordinate (P2) at ($(P2)+(Delta)$);
\coordinate (A) at ($(A)+(Delta)$);
\coordinate (B) at ($(B)+(Delta)$);


\draw 
   ($(P1)!\t!(P2)$)
   --
   ($(P1)!\tt!(P2)$);

\draw ($(P1)!\ttt!(P2)$) node {$r$};

\filldraw  (A) circle (1pt) node [right] {$A$};
\filldraw  (B) circle (1pt) node [right] {$~B$};

\coordinate (P1) at ($(P1)+(Delta)$);
\coordinate (P2) at ($(P2)+(Delta)$);
\coordinate (A) at ($(A)+(Delta)$);
\coordinate (B) at ($(B)+(Delta)$);


\draw 
   ($(P1)!\t!(P2)$)
   --
   ($(P1)!\tt!(P2)$);

\draw ($(P1)!\ttt!(P2)$) node {$r$};

\filldraw  (A) circle (1pt) node [right] {$A$};
\filldraw  (B) circle (1pt) node [right] {$~B$};


\draw ($(A)!\s!(B)$) -- ($(A)!\ss!(B)$);
\draw ($(A)!\s!(B)$) -- ($(A)!\ss!(B)$);
\draw ($(A)!\sss!(B)$) node {$s$};

