[CCNode visit] got a darkEdge « cocos2d for iPhone

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[CCNode visit] got a darkEdge

(10 posts) (2 voices)

Started 1 year ago by kitdastudio
Latest reply from kitdastudio

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kitdastudio
Member
hi all

i've got a question about the [visit] function of CCNode

the original image is good with clear outline, nothing special
it composes of 5 leaves sprites inside

then I want to use [CCNode visit] to copy it
and here's the code
```
-(CCSprite *)flattenSprite:(CCSprite*)sprite textureSize:(float)textureSize {

    CCRenderTexture *rt = [CCRenderTexture renderTextureWithWidth:textureSize height:textureSize];
    [rt begin];

    // store the original sprite position
    CGPoint p=sprite.position;
    //set original sprite to a target point for open GL to "visit"
    sprite.position=ccp(textureSize/2,textureSize/2);
    // open GL visit
    [sprite visit];
    //original sprite return to original point
    sprite.position=p;

    [rt end];
    return [CCSprite spriteWithTexture:rt.sprite.texture];
}
```
by this function i can optimize the performance of the application by limiting the amount of the sprites existing on stage
but the "copied sprites" got a dark edge around it
it looks weird - especially when the sprites are ovelaping each others

please tell me if you have any clues / anywhere got useful information about this dark edge issue
thank you so much

best
Kit
Posted 1 year ago #
araker
Moderator

It's probably a blending issue, try

[[rt sprite] setBlendFunc: (ccBlendFunc) {GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA}];

after you create the render texture.

Posted 1 year ago #
kitdastudio
Member

hi Araker - thanks
have tried to put this line [[rt sprite] setBlendFunc: (ccBlendFunc) {GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA}];

after [rt begin];
or
after [rt end];
or
set the sprite returned [returnedSprite setBlendFunc: (ccBlendFunc) {GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA}];

both got the same result as the screen capture above
thank you

Posted 1 year ago #
araker
Moderator

You should check which blend function the sprite gets when you display it normally. The blend function of the sprite of the render texture must have the same blend function. When you display the sprite normally (without a render texture) does it render correctly? If that's the case then this is a blending issue.

Posted 1 year ago #

kitdastudio
Member

hi Araker

thanks for the hint
but i got no blendings for the original sprite

composed as follow

-(id) init {
    if((self=[super initWithColor:ccc4(255,255,255,255)])) {
        self.isTouchEnabled = YES;

        //
        leaveGroup=[[CCSprite spriteWithFile:@"blank512.png" rect:CGRectMake(0, 0, 64, 64)]retain];
        //leaveGroup=[CCSprite spriteWithFile:@"leaf00.png"];
        for(int i=0;i<5;i++) {
            CCSprite *l=[CCSprite spriteWithFile:@"leaf00.png"];
            [l setAnchorPoint:ccp(0.5,0.0)];
            l.position=ccp(32,32);
            l.rotation=i*36;
            [leaveGroup addChild:l];
        }
        leaveGroup.position=ccp(160,240);
        [self addChild:leaveGroup];
    }
    return self;
}

the leaveGroup sprite is a container sprite init with a portion of the totally blank PNG
to test if the issue wasnt related to this totally blank PNG
I've tested with the line leaveGroup=[CCSprite spriteWithFile:@"leaf00.png"];
which is a normal way to add a sprite to stage

but the dark outline issue is still here

Posted 1 year ago #

araker
Moderator
Okay so even when you add the sprite normally it still has the dark outline. Then there's no blending issue in the render texture at least.

Cocos sets the blending function for your sprite internally when you initialize it with a image. The function differs whether your image has the colors premultiplied with the alpha value or not. When you set a breakpoint after you create the sprite you can look at the properties of the sprite. You'll either see

blendFunc.src = 1
blendFunc.dst = 771

or

blendFunc.src = 770
blendFunc.src = 771

In the first case change the blendfunction to the one in my first post, in the second case change it to {GL_ONE,GL_ONE_MINUS_SRC_ALPHA}.

Another thing you can try is to set the color format of the EAGLView to RGBA8, that's done in your app delegate..
```
EAGLView *glView = [EAGLView viewWithFrame:[window_ bounds]
					pixelFormat:kEAGLColorFormatRGBA8                // RGBA8 color buffer
					depthFormat:0   // 24-bit depth buffer
					preserveBackbuffer:NO
					sharegroup:nil
					multiSampling:NO
					numberOfSamples:0];
						];
```
Posted 1 year ago #

kitdastudio
Member

hi Araker

thank you so much for your detailed reply
I've tried different combinations and finally one worked

1. color format: RGB565 is fine, RGBA8 works too

2. for the original sprite, it is by default with blendFunc as follow
blendFunc.src = 1
blendFunc.dst = 771

3. {GL_ONE,GL_ONE_MINUS_SRC_ALPHA} works but not in the [rt sprite]
need to set it at the final sprite returned

- (void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    // touch point
    UITouch *touch=[[touches allObjects]objectAtIndex:0];
    CGPoint point=[touch locationInView:touch.view];
    point=[[CCDirector sharedDirector]convertToGL:point];

    // copyLeave function called to copy the original sprite and return a "flattened" sprite
    CCSprite *s=[self copyLeave:leaveGroup textureSize:64];
    // set the returned sprite position
    s.position=point;
    // improper lazy scaling for returning the sprite in the same orientation
    s.scaleY=-1.0;
    [self addChild:s];
    // setBlendFunc and finally things work like a charm !!! thanks to Araker
    [s setBlendFunc:(ccBlendFunc){GL_ONE,GL_ONE_MINUS_SRC_ALPHA}];

}

Posted 1 year ago #

kitdastudio
Member

can't really understand how GL_ONE,GL_ONE_MINUS_SRC_ALPHA thingy works
but here's an online tool helping us to visualize the settings
it looking great and helpful

http://www.andersriggelsen.dk/glblendfunc.php

best
Kit

Posted 1 year ago #
araker
Moderator

Good to hear you got it working. Which cocos version are you using, because that blendfunction is the default one of the render texture sprite since the first beta release of 1.0.

Posted 1 year ago #
kitdastudio
Member

my version is
static NSString *version = @"cocos2d v1.0.0-beta";

thanks alot for your patience and help

Posted 1 year ago #

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