10 replies to this topic

[vann]

The manual suggests that you can also define collisions using collision events (as opposed to seeting two fixtures in the same group).

1) I am wondering how to make two objects collide (and interact accordingly - like bounce) which arent in the same group through using a collision event - I can't seem to find a function to do this.

2) Is there a way use the collision events for collisions between objects with fixtures and objects without fixtures? Ortherwse whats a good way to test these? collision_circle etc. or place_meeting?

[JAk HAk]

I haven't encountered #1 or a solution to it yet, but #2 is easy enough. Physics objects still retain their sprite masks, just like any other object, so you can use place_meeting() with them or any of those collision detection functions. Just be mindful to update image_angle to phy_rotation so that it uses the orientation that it looks like it has (physics objects update phy_rotation instead and use that to draw their orientation by default).

[vann]

JAk HA, thanks for that, I was using this method, but thought I should check in case I was missing something more obvious

As for number 1 then, anyone else care to comment? Is this supposed to be possible? The manual makes it sound so.

I guess I need a Box2d equivalent of move_bounce_solid() but for two objects with fixtures which are not in the same collision group.

[vann]

bump

[vann]

Anyone? Is this (1) just not possible at the moment?

Edited by vann, 02 May 2012 - 11:34 AM.

[ChefDavid22]

Here is how I did it with my game here: http://www.eodongame...?ID=virustroids

Take a look at the game first to make sure that's the type of physics you are looking for. When you bounce into what I call the virus - both you and the virus float away from each other.

First off in the collision event:

while (place_meeting(x, y, other)) 
{ 
x -= lengthdir_x(1, direction); 
y -= lengthdir_y(1, direction); 
} 
move_bounce_all(true);

Then add the same thing in the collision even BUT make sure you click on the radio button "OTHER" at the top.

Then step 2:

My code only works if you are not holding down what ever button you coded in to make the player move forward. So what I did was add a variable called "cannotmove" set it 0 on creation then set it to 1 in this collision....

if cannotmove = 0
{
while (place_meeting(x, y, other)) 
{ 
x -= lengthdir_x(1, direction); 
y -= lengthdir_y(1, direction); 
} 
move_bounce_all(true);
cannotmove = 1;
alarm[0]=room_speed*1.5;
}

Then I made an alarm[0] that puts cannotmove = 0 after 1.5 seconds.

THEN in the code where I press "UP" to move forward I made sure to check first to see what the value of cannotmove is

if cannotmove = 0
{
speed = 1;
etc 
etc
}

I wouldnt say my code is perfect by any means but for my game and its theme it works fine enough for me.

Edited by ChefDavid22, 02 May 2012 - 03:00 PM.

[mrsmes]

that reminds me there is this one thing that really annoys me in the beta version of game maker studio, it has the time line actions but not the functions.
Back on topic: if your trying to make it roll and bounce that could take some experimenting.

[vann]

ChefDavid22,

Thanks for you reply but this isn't what I am looking for, I am wondering how to envoke physics collisions from box2D in the collision event, specifically how to do this without having two objects in the same collision group.

In the manual the caption for the third image in the entry for physics_fixture_set_collision_group(fixture, group) says:

These balls belong to different collision groups and they collide based on their collision event

What I can't work out is how to make them collide and react accordingly (using the physics engine) in their collision event.

Are any of the devs able to help clarify this, seems noone else has needed this functionality?

Thanks for any further help

[mrsmes]

i think it's so they can set a variable in the collision event to 1 and if the user clicks it the objects in the group with the variable set to one vanish or explode.

[vann]

I wouldn't get that it was limited to this from they way they have worded the manual. It says:

These balls belong to different collision groups and they collide based on their collision event

The picture which accompanies the third image specifically has a ball from collision group -2 colliding (ie, bouncing) with a ball from collision group 1.

Can someone please explain how to acheive this, or put me out of my misery and tell me its actually not possible (yet?)...

Thanks again.

[Joeben123]

I have just encountered this problem and after combing the forums I couldn't find anything useful. There is nothing in the guide or the wiki that explains it either. I am pretty surprised no one else seems to have this problem. Is everyone just putting objects in the same collision group if they want them to collide with physics?