load (draw);
load (vector_rebuild);

listarith : true;
doallmxops : true;
/* Gerade: T + r b */
T : [1,2,3];
b : [2,4,4];
A : [2,5,4];

/* r n*C / |n|  */
/* r ist die Länge der Projektion von A auf g */
  r : lsum(i,i,maplist("*",b,(A-T))) / |b|;
/* P ist der Lotpunkt des Lotes von A auf g */
  P : T + b*r/|b|;

s : T + 2*(P-T);

  str1 : strim("\"", string("set label '{/=25 g}' at "));
  label1 : concat (str1, s[1]+0.2, ",", s[2], ",", s[3]);
  /**/
  str2 : strim("\"", string("set label '{/=25 A}' at "));
  label2 : concat (str2, A[1]+0.2, ",", A[2], ",", A[3]-0.3);
  /**/
  str3 : strim("\"", string("set label '{/=25 P}' at "));
  label3 : concat (str3, P[1], ",", P[2], ",", P[3]+0.3);
  /**/
  str4 : strim("\"", string("set label '{/=25 T}' at "));
  label4 : concat (str4, T[1]-0.2, ",", T[2], ",", T[3]);

draw3d (
  line_width = 2,
  /*
  xrange = [-0.5, 5],
  yrange = [-0.5, 5],
  zrange = [-0.5, 5],
  */
  points_joined = true,
  point_size = 1,
  point_type = none,
  transparent = false,
  head_length = 0.1,
  color = red,
  points ([T, s]),
  color = blue,
  vector (T, A-T),
  color = black,
  line_type = dashes,
  points ([A, P]),
  /* */
  xtics = false,
  ytics = false,
  ztics = false,
  user_preamble = [
                "set noborder", 
                 label1, label2, label3, label4
                ],
  /* view = [91, 60], */
  dimensions = [600, 600],
  file_name = "projektiongerade",
  /* terminal = eps_color  */
  terminal = png  
);