Hello,
I want my enemies to be able to find covers. As a starter in 3dgs i did this.
I put dummy entities in cover positions in my level and set there enable scan on and made the enemy to scan for the covers using scan_entity.
for the trial the enemy successfully scanned the dummy entity on the cover position and i confirmed it by displaying result variable from scan_entity on screen. but when i try to point the enmy to you pointer returned by scan_entity the engine gives the empty pointer error. Also if i try to make the enemy turn to found object it doesn't turn. here is my code.



though it shows the result by scan_entity (i displayed on the screen using digits) that means that it successfully scans the entity but why it gives empty pointer error and why it doesn't turn to cover i don't know?

A few questions as a new starter.
Is my aproach for the cover is good or is there any better way?
which one is better suited for this task scan_entity, trace or c_scan? Does it slows down the game or is there any alternative?

Thank You!

In my ai system i used an other approach. After the level is loaded all cover point entities are detected and stored in an array. At runtime if taking cover is required, they are checked (player non visible and shortest distance to actor). Then pathfinding leads the actor to the cover point.

I would suggest to code this as a finite state machine, so you are able to react very differentiated. The gameplay looks much more realistic then.

Well, the c_scan function DOES set the "you" pointer to the closest entity found; However, the reason for the crash is propably that the scan did not find anything, so the "you" pointer remains empty.
You need to check if "you" is empty before you use it:

if(you != NULL)
... // go on here

BUT, snake's solution is much simpler and better either way, so I don't see why you should use c_scan. Do it like snake proposed, that's pretty certainly working.

Yes, i was wrong... Maybe this helps:

// store the cover point entities:

void ai_init_cover_points()
{
ENTITY* ent;

for(ent=ent_next(NULL), n_cover_points=0; ent!=NULL, n_cover_points<100; ent=ent_next(ent))
{
str_for_entfile(ai_filename, ent);
if(str_cmpni("coverpoint", ai_filename))
{
cover_point[n_cover_points]=ent;
n_cover_points++;
}
}
}

// get a cover point

ENTITY* ai_get_cover_point(ENTITY* actor)
{
ENTITY* cp;
var ad;
var i;

ad=10000;
cp=NULL;
for(i=0; i<n_cover_points; i++)
{
cover_point[i].skill1=vec_dist(cover_point[i].x, player.x);
cover_point[i].skill2=vec_dist(cover_point[i].x, actor.x);
if(cover_point[i].skill1>cover_point[i].skill2)
{
you=NULL;
c_trace(cover_point[i].x, player.x, IGNORE_PASSABLE|IGNORE_PASSENTS);
if(you!=player)
{
if(cover_point[i].skill2<ad)
{
cp=cover_point[i];
ad=cover_point[i].skill2;
}
}
}
}
return(cp);
}

Snake thank you very much for your time. Your idea seems very interesting let me understand and try your code then i will be back with the results.

Snake thanks for the cooperation your idea is great i will difinately try this idea in my next advanced projects. but for this i will go for the entity_scan bytheway i have uploaded my test level with my code which gives error please check it and diagnose the problem. I will be very thanks full.

[Note] all the codes are template based or copy paste from the aum projects because i wanted to quickly find a solution later i will improve code.

Cover.zip [345 kb]

everybody is welcome to check my code and provide solution thank you.

Ok. Will download and have a look...

Thanks once again i wil be waiting.