c# - Doom-like angle based sprite changing -

so, i'm trying make first person game used same sprite mechanics games doom, duke nukem , etc.

so far, can identify angle i'm @ in relation static objects, not rotating ones. have "enemies" change rotation , start following me, calculating tangent angle (mathf.atan2) doesn't take enemy's rotation in consideration.

here's code i'm using far, works objects dont rotate:

 int getangleindex()  {     var dir = cam.transform.position - transform.parent.forward;     var enemyangle = mathf.atan2(dir.z, dir.x) * mathf.rad2deg;      if (enemyangle < 0.0f)         enemyangle += 360;      debug.log("angle player is: " + enemyangle);      if (enemyangle >= 292.5f && enemyangle < 337.5f)         return 8;     else if (enemyangle >= 22.5f && enemyangle < 67.5f)         return 2;     else if (enemyangle >= 67.5f && enemyangle < 112.5f)         return 3;     else if (enemyangle >= 112.5f && enemyangle < 157.5f)         return 4;     else if (enemyangle >= 157.5f && enemyangle < 202.5f)         return 5;     else if (enemyangle >= 202.5f && enemyangle < 247.5f)         return 6;     else if (enemyangle >= 247.5f && enemyangle < 292.5f)         return 7;     else if (enemyangle >= 337.5f || enemyangle < 22.5f)         return 1;     else return 0; } 

i've searched hours , can't find solution :(

you [only] problem doesn't take rotation account - i'm guessing means you're not having trouble billboarding sprites, , rotation works when they're facing forward. end:

the dot product of vectors , b equal cos(theta)*magnitude(a)*magnitude(b). if vector camera object:

var = cam.transform.position - transform.parent.position 

and b object's forward:

var b = transform.parent.forward 

and know , b both have magnitude 1

a.normalize(); //b normalized 

then know equal cos(theta), theta angle between them.

var theta = mathf.acos(vector3.dot(a, b)) * mathf.rad2deg; 

however. theta shortest necessary angle - 0 180. given switch table there, know when we're hoping go around wrong way, we'll in wrong position. fix that:

if (a.x * a.z < 0)     theta = 360.0f - theta; 

then plug in , go. here's full file in project:

using unityengine;  public class spriteangler : monobehaviour {     public transform toface;     public spriterenderer tomanipulate;     public sprite[] mysprites;     private float theta;     private vector3 a;     void update()     {         tomanipulate.sprite = mysprites[getangleindex()];     }     int getangleindex()     {         = toface.position - transform.position;          a.normalize();         var b = transform.forward;          theta = mathf.acos(vector3.dot(a, b)) * mathf.rad2deg;          if (a.x * a.z < 0)             theta = 360.0f - theta;          if (theta >= 292.5f && theta < 337.5f)             return 7;         else if (theta >= 22.5f && theta < 67.5f)             return 1;         else if (theta >= 67.5f && theta < 112.5f)             return 2;         else if (theta >= 112.5f && theta < 157.5f)             return 3;         else if (theta >= 157.5f && theta < 202.5f)             return 4;         else if (theta >= 202.5f && theta < 247.5f)             return 5;         else if (theta >= 247.5f && theta < 292.5f)             return 6;         else if (theta >= 337.5f || theta < 22.5f)             return 0;         else return 0;     }      private rect guipos = new rect(0, 0, 720, 30);     void ongui()     {         gui.label(guipos, "angle player is: " + theta + " , forward=" + transform.forward + " , vectortotarget=" + a);     } } 

and if needs little more context, here's project: https://github.com/adamrgrey/22623013

i'd recommend hitting play watching scene window instead of game window.