GML Simple Problem: place_free() checking

[Posho]

Hello,

I'm stuck with the simplest of things. I'm looping through the whole room to add objects on empty spots like this:

for (var i=0; i<room_width; i+=len)
    for (var j=0; j<room_height; j+=len)
        if (place_free(i, j))
            instance_create_depth(i, j, 8, obj_water);

^ THIS works, but if I change the if condition from if (place_free(i, j)) to if (!place_free(i, j)) to add objects on top of non-empty spots it doesn't do anything. Why?

 

[Nidoking]

What is the bounding box of the object running this code? Is it an obj_water, or an object that has the same bounding box as an obj_water? Or is it something else?

 

[Posho]

What is the bounding box of the object running this code? Is it an obj_water, or an object that has the same bounding box as an obj_water? Or is it something else?

The object running the code is spriteless. I thought it was somehow an issue involving collision considering the manual section for place_free() mentions it, so I assigned a sprite the same size as all the other objects in the game, but the outcome is still the same.

[Edit]
Also doesn't work if I make all the other objects solid.

 

[Nidoking]

Well, place_free basically says "Do I, the instance executing this function, lie on top of a solid instance when placed at these coordinates?" Make sure that in addition to the sprite, the object running the code also has a bounding box the same size as the instances you're trying to place. You might also consider collision_rectangle instead of instance_place, so you don't need an actual instance with a bounding box to run the check.

 

[Posho]

What is the bounding box of the object running this code? Is it an obj_water, or an object that has the same bounding box as an obj_water? Or is it something else?

For some reason it started working as intended when I added a sprite to the object. It didn't save the first time but it's working now.
THANK YOU

 

[Sabnock]

Hello,

I'm stuck with the simplest of things. I'm looping through the whole room to add objects on empty spots like this:

for (var i=0; i<room_width; i+=len)
    for (var j=0; j<room_height; j+=len)
        if (place_free(i, j))
            instance_create_depth(i, j, 8, obj_water);

^ THIS works, but if I change the if condition from if (place_free(i, j)) to if (!place_free(i, j)) to add objects on top of non-empty spots it doesn't do anything. Why?

Looks like you forgot your {}

for (var i=0; i<room_width; i+=len) {
    for (var j=0; j<room_height; j+=len) {
        if (place_free(i, j)) instance_create_depth(i, j, 8, obj_water);
   }
}

although i have just tried some code without {} and it works so go figure ???!!!

 

[RefresherTowel]

Looks like you forgot your {}

for (var i=0; i<room_width; i+=len) {
    for (var j=0; j<room_height; j+=len) {
        if (place_free(i, j)) instance_create_depth(i, j, 8, obj_water);
   }
}

although i have just tried some code without {} and it works so go figure ???!!!

If there's only a single line to be executed after an if, for, etc statement, you can omit the curly brackets and it will run fine. IMO, though, it's better to be consistent and always include curly brackets just so you don't cause yourself an unnecessary bug by doing something silly while omitting the brackets, but that's just me.

 

[Sabnock]

it's better to be consistent and always include curly brackets just so you don't cause yourself an unnecessary bug

i couldn't agree more. it looks confusing to me and would make it much harder to read if looking for errors but each to their own. if it works it works.