Can collide with sprite frame x but not with frame y

[xronn]

Hi,

 

I have a sprite trap that loops very slowly frame 0 its safe but frame 1 it's deadly, can you make a player collide with the same sprite but a different frame?

 

Also am I right in thinking that if you can do this you can make it remove health from the player on a certain frame?

thanks

[ram64]

You could add an if-statement in the update loop that checks the frame of the trap sprite and then do a collision:

update() {...if(trap.frame == 1) game.physics.collide(trap, player, onTrapHit, null, this);...}function onTrapHit(trap, player) {   // do trap damage}

In this example you can consider that the trap is deadly on frame 1 (you can test against any other frame or frames). The onTrapHit() is a collision callback in which you do all the damage logic. 

[xronn]

Thank you, extremely useful thanks again for your help, could someone tell me what each parameter does; 

game.physics.collide(trap, player, onTrapHit, null, this);

is this correct 

trap = sprite variable name
player = sprite variable name 

onTrapHit = call back for the next function 
null = not sure
this = to tell the game object what we refer too? 

[seiyria]

Adding to this, is there a way to do this with a group? I have a group of sprites that I want to check for collision during a certain frame. It's the same frame for all of them.

[seiyria]

I figured this out: had to use the second callback parameter in the collide function to check the frame.

[xronn]

Seiyria could you share what you wrote for the group collision as I'm trying that now.

 

I tried to just take some health every time the frame was active to see if I'm on the right path, I get no errors but has no effect:

if(trapGroup.frame == 2){   hero.health -= 1;}

[seiyria]

Sure.

this.game.physics.collide(this.game.player.ref, this.fadingBlocks, function(ref, block) {    if (ref.body.touching.down) {      return _this.game.player.onBlock = true;    }  };}, function(ref, block) {    return block.currentFrame.index === 0;  };});

This will not work verbatim, it's edited from my compiled coffeescript and likely isn't semantically correct. As for how it works, I make usage of the fourth parameter in the function to determine if the collision can happen with the group "fadingBlocks". Hopefully that helps.