How to use openGL line drawing in cocos2d - cocos2d-iphone

Question

I like to draw a line, but cocos2d inside ccDrawLine serrate, how to draw a blurring of the line, who can help me?
ccDrawLine( ccp(StartP.x, StartP.y), ccp(EndP.x, EndP.y) );

Answer 1

I did not use ccDrawLine but I created a line with a Sprite and I animated it (see code below). In this way I was able to use custom line images made (but nevermind. that's how I did).
If you want to stick to primitives I guess you should set the opacity of the line primitive (see this post which explains how) and then you could create a sequence of action that set the opacity level (e.g. start with opacity at 100%, then 75%, then back to 100% like I did with my images but using the method in the link above) to get the blurring effect..
Code using images:
CCSprite * string = [self getChildByTag:tag];
[string setOpacity:100];
NSMutableArray* frames = [[NSMutableArray alloc]initWithCapacity:3];
NSString*lineFrame = [NSString stringWithString:#"line0.png"];
CCSpriteFrame* frame = [[CCSpriteFrameCache sharedSpriteFrameCache]spriteFrameByName:lineFrame];
[frames addObject:frame];
lineFrame = [NSString stringWithString:#"line1.png"];
frame = [[CCSpriteFrameCache sharedSpriteFrameCache]spriteFrameByName:lineFrame];
[frames addObject:frame];
lineFrame = [NSString stringWithString:#"line0.png"];
frame = [[CCSpriteFrameCache sharedSpriteFrameCache]spriteFrameByName:lineFrame];
[frames addObject:frame];
CCAnimation* anim = [CCAnimation animationWithFrames:frames delay:0.1f];
CCAnimate* animate = [CCAnimate actionWithAnimation:anim];
//CCRepeatForever* repeat = [CCRepeatForever actionWithAction:animate];
[string runAction:animate];
[string setOpacity:75];
Hope that this helps..

Answer 2

#import "cocos2d.h"
#interface CClineSprite : CCLayer
{
CCRenderTexture * renderTarget;
NSMutableArray * pathArray;
CCSprite * pathBrush;
CGPoint prePosition;
}
-(void)setLinePosition:(CGPoint)position;
-(void)setLineOpacity:(GLubyte) anOpacity;
-(void)setLineScale:(float) scale;
-(void)setLineColor:(ccColor3B) color;
#end
#import "CClineSprite.h"
#implementation CClineSprite
- (id) init
{
self = [super init];
if (self)
{
CGSize s = [[CCDirector sharedDirector] winSize];
renderTarget = [CCRenderTexture renderTextureWithWidth:s.width height:s.height];
[renderTarget setPosition:ccp(s.width/2, s.height/2)];
[self addChild:renderTarget z:1];
pathBrush = [CCSprite spriteWithFile:#"dots.png"];
pathBrush.color = ccWHITE;
[pathBrush setOpacity:100];
[pathBrush setScale:0.5];
pathArray = [[NSMutableArray alloc]init];
}
return self;
}
-(void)setLineOpacity:(GLubyte) anOpacity
{
[pathBrush setOpacity:anOpacity];
}
-(void)setLineScale:(float) scale
{
[pathBrush setScale:scale];
}
-(void)setLineColor:(ccColor3B) color
{
[pathBrush setColor:color];
}
-(void)setLinePosition:(CGPoint)position
{
[pathArray addObject:[NSValue valueWithCGPoint:position]];
[self renderPath];
}
- (void) renderPath
{
[renderTarget clear:0 g:0 b:0 a:0];
[renderTarget begin];
for (int i = 0; i < pathArray.count-1;i++)
{
CGPoint pt1;
CGPoint pt2;
[[pathArray objectAtIndex:i] getValue: &pt1];
[[pathArray objectAtIndex:i + 1] getValue: &pt2];
float distance = ccpDistance(pt1, pt2);
if (distance > 1)
{
int d = (int)distance;
for (int i = 0; i < d; i += 10)
{
float difx = pt2.x - pt1.x;
float dify = pt2.y - pt1.y;
float delta = (float)i / distance;
[pathBrush setPosition:ccp(pt1.x + (difx * delta), pt1.y + (dify * delta))];
[pathBrush visit];
}
}
}
[renderTarget end];
}
#end
USAGE:
CClineSprite* streak = [CClineSprite node];
[self addChild:streak z:999];
[streak setLinePosition:associatedTurtleObject.position];
[streak setLineScale:0.4];
To dynamically update or extend the line just use
[streak setLinePosition:ccp(x,y)];
Hope this will give you more flexibility for use