Q: How can I make an entity move to the specified location?

A: Here's an example that moves an NPC character towards its goal using primitive, and yet fully functional obstacle avoidance code.

 

ENTITY* goal;

 

action npc_goal() // attach this action to the destination entity

{

       goal = my;        

}

 

action goal_tracker() // attach this action to your NPC character

{

       while (!goal) {wait (1);} // wait until the goal entity is loaded

       VECTOR temp, temp_angle;

       var npc_speed = 5;

       var covered_dist, i;

       while (1)

       {

               my.skill10 += 6 * time_step; // 6 gives the animation speed

               vec_set (temp.x, my.x); // trace 10,000 quants below the npc entity

               temp.z -= 10000;

               temp.z = -c_trace (my.x, temp.x, IGNORE_ME | IGNORE_PASSABLE | USE_BOX) + 20; // play with 20

               temp.x = npc_speed * time_step;

               temp.y = 0;

               ent_animate(my, "walk", my.skill10, ANM_CYCLE);

               covered_dist = c_move (my, temp.x, nullvector, IGNORE_PASSABLE | GLIDE);

               if (covered_dist < 0.1) // the npc is stuck?

               {

                       my.pan += 90 - random(180); // then add a random angle to its pan angle

                       i = 0;

                       while (i < 10) // walk in the new direction for 10 frames, play with 10

                       {

                               c_move (my, temp.x, nullvector, IGNORE_PASSABLE | GLIDE);

                               ent_animate(my, "walk", my.skill10, ANM_CYCLE);

                               i++;

                               wait (1);

                       }                                

               }

               else // the npc can move? Then rotate it towards the goal again!

               {

                       vec_set(temp_angle, goal.x);

                       vec_sub(temp_angle, my.x);

                       vec_to_angle(my.pan, temp_angle);

                       my.tilt = 0;

               }

               if (vec_dist(goal.x, my.x) < 50) // the npc has found the goal entity?

                       break; // then get out of the while loop!

               wait (1);

       }

       // the goal was reached here

       ent_animate(my, "stand", 0, 0); // switch to "stand"

}