GameMaker Collision with one object precise and one not-precise

[Skull_k]

Hi,

I use IDE V2.1.0.212 and run time 2.1.0.136.
In GMS2 manual, we can find the following sentence with the picture for place_meeting :
"This will work for precise collisions, but only if both the instance and the object being checked for have precise collision masks selected otherwise only bounding box collisions are applied. "

I tried to reproduce the example but i didn't have the result expected :
-I created two sprites : a cricle with precise collision ( i chose "precise (slow)" in collision mask)
a rectangle with not precise collision (i chose "Rectangle (fast)" in collision mask).

-I create two objects : a circle with the circle sprite (collision mask is "Same As Sprite")
a rectangle with the rectangle sprite (collision mask is "Same As Sprite")

In circle object step event, i put this code (it is my only code in the game):
if place_meeting(x,y, O_Rectangle) {
show_message("Collision") ;
}
And i placed the circle and the rectangle like this in the room :


I expected to have a message "Collision" but game maker does not detect the colision.
When i put sprite circle with not-precise collision mask, it detects a collision...

So, does someone could explain why i have this behaviour ?

 

[Jakylgamer]

because when using precise the circle in your image is not colliding with the square its off by like 2 or 3 pixels.
precise will use the shape of the sprite along the edges.
when its not precise it will use a square for collision mask.

example img

Spoiler

 

[Skull_k]

Hello,

Thank you for your reply, but my point is that it is in contradiction with the manual. In the manual, we can see the following picture :


So, if i understand well the manual, in my example, game maker should "switch the circle to not-precise collision" because the rectangle is not precise when we apply place_meeting. But this is not the case in my example.

So, is there a mistake in the manual or i don't understand well the manual ?

 

[Jakylgamer]

i think the manual is saying if one has precise collision checking and the other doesnt it will still cause a collision between the 2 but it will not appear to be precise because one is not using precise collision checking.

 

[CloseRange]

The only way to alter the mask in the code is to change the mask_index and even then you cant say 'precise' or 'not-precise' that only changes the sprite_mask to refrence.

place_meeting will always check if the masks are touching each other. If you set both masks to be not-precise then yes you would get a message saying "Collision"

 

[Skull_k]

Thank you for your response.
I just tried to reproduce the example, and i didn't have the result that i expected.
Anyway, i understand that GM will check the collision mask seting up in sprite editor.