Here is the setup. I have a orthogonal tile map made with Tiled. There are 5 layers. The bottom 4 comprise the background, while the top layer is the foreground that I will refer to as the “tree” layer. I have a hero sprite that I have added as a child of the tile map at the same node zorder as the tree layer.
The issue that invariably comes up with this scenario is that I want my hero to be in front of trees that he is “below”, but behind those trees that he is “above”. Below and above are determined by the Y coordinate of the hero versus the Y coordinate of any given tree.
The Cocos2d programming guide contains a section for tile maps, and in that section it specifically discusses how to achieve the affect I have described. This information can be found here.
http://www.cocos2d-iphone.org/wiki/doku.php/prog_guide:tiled_maps
The solution is pretty simple. Enable the depth buffer in my code. Add a cc_vertexz property with a value of -1000 to each layer that the hero will be above. Then add a cc_vertexz property to the tree layer with a value of “automatic” as well as a cc_alpha_func property with a value of .5. Then as your hero moves re-adjust its sprite’s vertexz value based on its position within the map.
I did all this and it worked great. However, a problem appeared as soon as I added other “enemy” sprites to this map. As with the hero sprite these sprites were added to the map with the same node zorder as the tree layer, and they too have their vertexz values changed based on their Y coordinate within the map. It should be noted that the hero sprite is added after the enemy sprites. In addition, both the hero and enemy sprites are animated and their textures are not part of the tile map textures. Based on the Cocos2d documentation this should not matter.
The problem is this. If my hero is below an enemy sprite on the map then everything looks and works fine. However, if my hero is above an enemy sprite on the map then as the enemy passes over the hero sprite the background comes through rather than the hero sprite. The best way to describe it is to say that as soon as the enemy sprite begins to pass over the hero sprite, the transparent areas of the enemy sprite begin to fill with the background and the hero sprite is partially obscured until then enemy sprite moves off the hero. It is like the hero sprite is not there.
I know this is related to the order that the sprites are added to the map, because if I change this and have the hero sprite added to the map before the enemy sprites, then the effect reverses in that the background comes through the transparent areas of the hero sprite rather than the enemy sprites. It is almost like the vertexz property is not absolutely determining the order that things are drawn.
Looking into this it appears to be a blending issue and I found what seems to be the solution, which is to subclass the CCSprite class and override the draw method with the following:
-(void) draw {
glEnable(GL_ALPHA_TEST);
glAlphaFunc( GL_GREATER, 0 );
[super draw];
glDisable(GL_ALPHA_TEST);
}
The problem however is that this code is not applicable to the version of Cocos2d that I use, which is Cocos2d 2.1. In addition this appears to be handled by the CCTMXLayer drawing function if automatic vertexz is enabled. As such I do not know if subclassing CCSprite would just be redundant. See below for how CCTMXLayer handles this:
// CCTMXLayer drawing function -(void) draw
{
if( useAutomaticVertexZ_ ) {
glEnable(GL_ALPHA_TEST);
glAlphaFunc(GL_GREATER, alphaFuncValue_);
}
[super draw];
if( useAutomaticVertexZ_ )
glDisable(GL_ALPHA_TEST);
}
I am not new to Cocos2d, but I am very new to anything related to OpenGL. So in short, is the solution just to subclass CCSprite and find the Cocos2d 2.1 equivalent to the above code snippet, or am I simply doing something wrong? I suspect the latter.
Any help would be very much appreciated. Thanks!
This has been resolved. The solution was to use the following on my sprites or sprite sheets as the case may be:
mySprite.shaderProgram = [[CCShaderCache sharedShaderCache]programForKey:kCCShader_PositionTextureColorAlphaTest];
This essentially takes the place of sub-classing CCSprite and overriding the draw method, which is the prescribed method for Cocos2d 1.x, whereas I am using Cocos2d 2.x.
Related
I am trying to create a simple platformer game in C++ with SDL, although am having trouble implementing animated sprites into the game. Linked is my git repo.
As you will see i'm currently having difficult trying to draw a single portion of the sprite sheet as the player sprite and looping through it to animate it. At the moment the entire sprite sheet that contains the player sprites is being squished into a 32 pixel rectangle. I have looked into SDL_RenderCopy although changing the variables that I pass to the method has no affect.
https://github.com/mountainfolks/Platformer_SDL
Have you stepped through your code to see which draw call you're hitting? AnimatedSprite inherits from Sprite, but you don't have Draw set as virtual in the base class, so you're actually calling Sprite::Draw. That would explain the behavior that points to the source rectangle being null.
I need to create an object that contains several sprites (2 for simplicity: the game object and its' shadow).
I need to compose them into the same class, so having the following questions:
what is the best ancestor class to the described one?
I used CCNode for this purpose. I overridden its draw method in the following way:
- (void)draw {
[super draw];
[_item draw];
[_itemShadow draw];
}
and suddenly found that need to change all other CCNode methods in the same way. For ex. change position, visible, etc. in order to change these properties in both Sprites my custom container aggregates:
#interface NBChecker : CCNode {
CCSprite *_item;
CCSprite *_itemShadow;
}
#end
There is the other way I see - to make both sprites parent property pointing to self. This should synchronise positions, visibility, etc. for these sprites.
Who has better ideas?
Would like to use aggregation and not sure I'm right in my thoughts.
Thanks!
Scrap the draw code. All you need to do is to add the two sprites as children of the CCNode subclass. Write your logic code in the CCNode subclass and have two ivars for each sprite for easier access (like you already have).
You don't need to draw the sprites yourself as long as they are part of the scene graph.
The sprites will move and rotate relative to their parent automatically. Move the node to move the sprites in unison, etc.
Does anyone know how to change the blending mode for a specific sprite in Cocos2d 2.x to GL_FUNC_SUBTRACT?
Ive tried a few things, but basically I'm trying to create a layer mask using a white (or black) circle and hiding the alpha.
You could try implementing your wrapper Sprite for that purpose. That class (let's say SubSprite) should inherit the CCNode class and have a single member, a regular CCSprite that you want to draw with GL_FUNC_SUBTRACT.
Override the draw method with something like this:
-(void) draw{
int oldEquation;
glGetIntegerv( GL_BLEND_EQUATION_ALPHA, &oldEquation);
glBlendEquation( GL_FUNC_SUBTRACT );
[targetSprite draw];
glBlendEquation( oldEquation );
}
I have not tried it out, but it should work and you do not have to rewrite the whole sprite drawing function.
I'm using cocos2d 1.0.1.
I've created a CCSpriteBatchNode, it includes a CCSprite (let's name it parentLayer) which includes some X number of childs(CCSprites).
The problem is - when I rotate parentLayer all sprites (childs) correctly displayed, however bounding boxes are at the same place (where they've been before rotation), so world coordinates of those sprites won't be changed.
Off course, all of the above works great without CCSpriteBatchNode. But, I would like to use batch node due to amount of sprites involved.
The question is, is there any way to update bounding boxes & child positions correspondingly?
How many sprites are we talking about? I would just go with a fast enumeration call to rotate each one individually. I nave never noticed a performance hit when doing this, have you?
CCArray *listOfChildren = [parentLayer children];
for (CCSprite *sprite in listOfChildren) {
[sprite setRotation:someValue];
}
In the isometric tiled map z-ordering example for cocos2d-iphone, they use an object that is already in the tilemap as the player sprite, which is rendered as moving through the trees.
Is there a way to use a random CCNode, created though code (not in the tmx file, and not part of the sprite sheet), and have it z-ordered correctly with the tilemap? addChild is not supported on a CCTMXLayer, and the gives an error when using that reads:'addChild: is not supported on CCTMXLayer. Instead use setTileGID:at:/tileAt:'.
There's got to be a way to have a CCNode (let's say a simple CCSprite) z-order correctly with a tilemap, either using cocos2d's API, or some z-buffer technique. Any pointers?
The CCTMXLayer doesn't support adding tiles at runtime because it's implemented with all sprites on a single spritesheet. Because of this implementation detail you also can't call setTexture on an individual tile.
The easiest solution would be to have the sprite you want to use on the spritesheet at the beginning. If you can't do this because it's generated at runtime or something, the next best thing (without touching cocos2d code) would be to modify the spritesheet.
Put a dummy tile in the spritesheet you're using for the TMXLayer and then, once you have the image you want to use, write it to the spritesheet using CCRenderTexture or something and use the newly generated Texture as your TMXLayer's texture.
You could also modify the CCTMXLayer to allow for your functionality but it sounds like you want to avoid that.
If you want to add a tile to say tile (x,y) ( (x,y) in Tiled Map editor coordinates ) then use the following code -
myTileMap is the reference to the CCTMXTiledMap object.
CCTMXLayer *layer=[myTileMap layerNamed:#"yourlayer"];
NSAssert(floorLayer !=nil, #"Ground layer not found!");
CGPoint tileAddPosition = [layer positionAt: CGPointMake(x,y)];
//Create your CCNode or CCSprite or whatever...say object name is **tileToBeAdded**
tileToBeAdded.anchorPoint = CGPointZero;
tileToBeAdded.position = tileAddPosition;
[myTileMap addChild:addedTile z:1];