Detecting Collisions With TMXTiledMap?

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Detecting Collisions With TMXTiledMap?

(32 posts) (7 voices)

Started 2 years ago by SDKTutor
Latest reply from mchawla

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SDKTutor
Member

I am making a game where it scrolls and you have to jump on these platforms, and if you don't, you fall and die. This is my code for detecting if on a platform:

CCTMXLayer *layer = [tilemap layerNamed:@"Layer 0"];
int posX, posY;
posX = sprite.position.x;
posY = sprite.position.y - 25;
unsigned int tile = [layer tileGIDAt:ccp(posX,posY)];
if(tile == 0){
// standable
}
else {
// not standable
}

When I do that code, the sprite is always standable. What is wrong?

Posted 2 years ago #
exorcyze
Member

I'm not sure why you have the postion.y - 25, but there are a couple things to note:

1) tileGIDAt takes in a *tile* position, not a pixel position.
2) You likely set the registration for the TMXTileMap to 0,0 which means bottom left of the map is 0,0 position, and y increases the higher up on the map you are. This is great, except that the tileGIDAt references from the top left, so 0, 0 is the top left tile on your map.

To get your tile position you will need to take the (tilemapPixelHeight - spritePixelPositionY) / tileSize and the spritePixelPositionX / tileSize and pass those into the tileGIDAt.

Hope that helps. =)

Posted 2 years ago #
SDKTutor
Member

So I have changed the code to this:
posX = (480 - sprite.position.x) / 32;
posY = (320 - sprite.position.y) / 32;

It is still does the same thing. Where am I going wrong?

Posted 2 years ago #
exorcyze
Member
You shouldn't need the 480 - for the x position unless your registration point for your map is 480 pixels from the left.

Have you tried a loop to see what tiles reside where?

IE:
```
for ( int y = 0; y < 10; y++ ) {
    for ( int x = 0; x < 10; x++ ) {
        int mygid = [layer tileGIDAt:ccp( x, y )];
        NSLog( @"GID at %i, %i = %i", x, y, mygid );
    }
}
```
Just to verify the output is what you expect. =)
Posted 2 years ago #
SDKTutor
Member

When I did that. It says it is ALWAYS 0. Never anything else. Do you know why that is happening? Also, in the code CCTMXLayer *layer = [tilemap layerNamed:@"Layer 0"];
What should the layerName by?

Posted 2 years ago #
exorcyze
Member

The layer name that you pass in should match what you see in tiled. And I can't remember offhand, but I think that tileGidAt returns 0 if a tile isn't found there ( I was looking at your code backwards, reading it as != 0 is standable ). Try putting another tile type on your map to verify. I actually have my first spot in my tileset blank hence me not recalling offhand. =)

Posted 2 years ago #
SDKTutor
Member

This is what my map.tmx file says:

<?xml version="1.0" encoding="UTF-8"?>
<map version="1.0" orientation="orthogonal" width="1700" height="10" tilewidth="32" tileheight="32">
<tileset firstgid="1" name="t" tilewidth="32" tileheight="32">
<image source="t.png"/>
</tileset>
<layer name="Layer 1" width="1700" height="10">
<data encoding="base64" compression="gzip">
H4sIAAAAAAAAA+3ci47jIAxA0XT6//88D......."shortened up a lot"==
</data>
</layer>
</map>

So should I put the layer name to be "Layer 1"?

Posted 2 years ago #
exorcyze
Member

Yup, that should be your layer name =)

Posted 2 years ago #
SDKTutor
Member

It doesn't quite work. 99% of the time it says 0. Occasionally is says 1,2, or 3.

Posted 2 years ago #
riq
Key Master

meta suggestion: try to use a more descriptive subject like: "Detecting collisions with TMXTiledMap". Thanks.

Posted 2 years ago #
SDKTutor
Member

Can someone please help me figure this out?

Posted 2 years ago #
SDKTutor
Member

Bumb.... anyone??? Please help.

Posted 2 years ago #
Questor
Member

Quote:
It doesn't quite work. 99% of the time it says 0. Occasionally is says 1,2, or 3.

0, 1 2, and 3 are all valid tile values. So not sure what the issue is.

However, according to your previous post, your tilemap is 1700 blocks wide...it is going to be very hard to debug something that large. Just create a 10x10 block tilemap and put a different tile in each location (or to start just fill each *row* with a different tile so it is even easier to debug). Then use exorcyze's loop and you should be able to understand how the parsing of tiles is done. Once you understand the layout of a small 10x10 tilemap, you make it as big as you need (within reasonable limits of course).

Regards,
Q

Posted 2 years ago #
SDKTutor
Member
Ok thanks. I see how it works now. It works if it is just stationary... but if I were to let's say do this:
```
id moveBy = [CCMoveBy actionWithDuration:3 position:ccp(-320, 0)];
	[tilemap runAction:moveBy];
```
It doesn't work. If I can't move the tilemap by doing that... then how am I supposed to move it?
Posted 2 years ago #

neophit
Member

If the tilemap's position is not (0,0) then you need to calculate the sprite's position relative to the tilemap's position. This can be done using convertToNodeSpace.

CCTMXLayer *layer = [tilemap layerNamed:@"Layer 0"];
int posX, posY;
posX = sprite.position.x;
posY = sprite.position.y - 25;
CGPoint nodeSpace = [tilemap convertToNodeSpace:ccp(posX,posY)];
posX = floor(nodeSpace.x / tilemap.tileSize.width);
posY = floor(tilemap.mapSize.height - (nodeSpace.y / tilemap.tileSize.height));
unsigned int tile = [layer tileGIDAt:ccp(posX,posY)];
if(tile == 0){
// standable
}
else {
// not standable
}

I have not tested this code.

Posted 2 years ago #

SDKTutor
Member

I have just tested it and it doesn't work. It crashes once it scrolls a certain distance...... the part that has me puzzled is that if I use the for loop at the beginning to get the grid id of all the places and then move the tilemap 100 pixels to the left and then get them again, it doesn't read out new ids of them. It doesn't change. They are exactly different even though the tilemap has moved.

Posted 2 years ago #
SDKTutor
Member

Anyone?

Posted 2 years ago #
leothenerd
Member

SDKTutor
It doesn't quite work. 99% of the time it says 0. Occasionally is says 1,2, or 3.

How could that happen?
You meant each time you loop through the tileset, the tile ID will be different?
Does your code change tile ID at all?

Posted 2 years ago #
neophit
Member

The for loop above is getting the GID for the first 10x10 tiles in your tilemap. Moving the tilemap will not change the GID for those tiles.

Take a look at the programming guide for a visual illustration of the tile coordinates.

Posted 2 years ago #
SDKTutor
Member

@leothenerd
No it doesn't. Not at all. I took the readings before it moved and then after it moved and compared them, not one difference.

Posted 2 years ago #
SDKTutor
Member

Please help....

Posted 2 years ago #
Questor
Member

SDKTutor,

I don't understand why you are even trying to move the tilemap. Why don't you use a parallax view and simply scroll the view?

If you have not already done so, I would strongly suggest running the cocos2d testbed and look at the examples. Alot of information and helpful coding practices can be gained by going through them all and finding ones that demonstrate the functionality you are looking for. As a matter of fact there is a example in the testbed that uses TMXTileMaps in conjunction with a parallax scrolling view.

Regards,
Q

Posted 2 years ago #
SDKTutor
Member

How would I then check to see if the stick figure is on the tile then because you couldn't use the CCTMXLayer *layer = [tilemap layerNamed:@"Layer 1"];

Also I searched in the testbeds and couldn't find the example with "TMXTiledMaps" in them.

Posted 2 years ago #
Questor
Member

In the testbed it is called the TileMapTest. It has both tga and tmx tilemaps.

As for knowing whether a figure is on a particular tile, that is really not dependent upon the position of the tilemap (as scrolling the tilemap is really just an adjustment in the view position of the CCLayer or the Parallax view). In your example, it is the change in the position of the character sprite vs the GID of the tile beneath the sprites coords.

I cannot tell you much more than that as I prefer to use a physics engine for collision detection, etc.

Regards,
Q

Posted 2 years ago #
SDKTutor
Member

Just wondering. How would you go about doing that in a physics engine (the one that you use)?

Posted 2 years ago #
Questor
Member

SDKTutor,

The box2d (physics engine) testbed is included in the cocos2d testbed. Take a look at those examples. The documentation is a little outdated, but between the documentation and the test examples, you should have all the info you need to learn how to use the collision detection (as well as everything else).

Documentation: http://www.box2d.org/manual.html

Also, if you google box2d and cocos2d you should find numerous tutorials and articles.

Regards,
Q

PS (The other physics engine included inside cocos2d is Chipmunk, I don't know alot about it, but it is considered excellent as well.)

Posted 2 years ago #
SDKTutor
Member

Thanks for the help. I wish I could get someone to help me with collisions without a physics engine.

Posted 2 years ago #
SDKTutor
Member

Can someone please answer how to scroll using the Parallax node and still be able to get the GID of something in a TMXTiledMap????!?!?!?!?

Posted 2 years ago #
SDKTutor
Member

Someone? Anyone? Sorry for necro-posting but I need help!

Posted 2 years ago #
SDKTutor
Member

Please help!!! I will be willing to send the source code of the game for you to look at if you need it but I need to trust you to not use the idea or give anyone else the code.

Posted 2 years ago #

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