CCSpriteBatchNode: Does the Child of Child receive drawing performance gains?

Question

I have a CCSpriteBatchNode with a configuration like this:

CCSpriteBatchNode
    ChildA1
        ChildB1
        ChildB2
        ....
        ChildB999
    ChildA2
    ChildA3
    ...

Where all children (ChildA1,ChildB1,ChildA2...) are CCSprite objects. The CCSpriteBatchNode and all children but ChildA1 is created via:

[CCSprite spriteWithSpriteFrameName:@"FileName.png"];

ChildA1 is created like this:

// Create Parent Sprite
CCSprite* childA1 = [[CCSprite alloc] init];
childA1.contentSize = CGSizeMake(37.5,37.5);
childA1.anchorPoint = ccp(0,0);
[batchNode addChild:childA1 z:0 tag:1];

// Add Child Sprites
[childA1 addChild:childB1 z:0 tag:1];
[childA1 addChild:childB2 z:0 tag:1];
[childA1 addChild:childB3 z:0 tag:1];
// Continue adding childB4-childB999

Note: This renders just fine, and I see the output I expect, where childB1's position is relative to childA1, and moving childA1 results in childB1 moving.

My question is this: Will I see a performance gain in the drawing each of childB1-childB999? From what I understand, the CCSpriteBatchNode optimizes the drawing of all children within a CCSpriteBatchNode by drawing all its child CCSprites together. Does this also apply to the children of those CCSprites?

For those who want to know why I'm doing this: There are many layers within this game and grouping CCSprites inside of a CCSprite within a CCSpriteBatchNode allows me to manipulate a group of CCSprites by manipulating only the parent of that group of sprites.

Answer 1

Short answer is, yes, CCSpriteBatchNode will make one draw call for all child nodes including all indirect descendants.

However, whether or not this performs better than using regular CCSprites depends on how often you are modifying the sprites. When you use a CCSpriteBatchNode, every time you modify a sprite, it will need to recalculate the texture atlas quad coordinates for that sprite and all its children using the CPU rather than the GPU. For your example, if you move the position of ChildA1, the coordinates for ChildB1 to ChildB999 will be recalculated before the next frame is rendered. In most applications, the reduction in openGL draw calls out weights the cost of the extra calculations, as draw calls are relatively expensive, but ultimately it will depend on your application and how it uses the sprites -- so I would suggest taking actual measurements for your application if this is a performance bottleneck.