Cocos2d Drawing App Making Lines - ios

Question

I am making a very simple drawing application. I got the lines to draw using the ccTouchMoved event. I am putting all the touch moved moved points into an array and then using a for loop to draw a line between all the points. Now, I do not want to join the points when I have lifted my finger and started new line drawing. I got that part working too but now whenever I begin a new drawing the whole screen flicker.
//
// HelloWorldLayer.mm
// DrawPuppets
//
// Created by Mohammad Azam on 12/11/12.
// Copyright __MyCompanyName__ 2012. All rights reserved.
//
// Import the interfaces
#import "DrawPuppetLayer.h"
#import "AppDelegate.h"
#import "PhysicsSprite.h"
enum {
kTagParentNode = 1,
};
#pragma mark - HelloWorldLayer
#interface DrawPuppetLayer()
-(void) initPhysics;
-(void) addNewSpriteAtPosition:(CGPoint)p;
-(void) createMenu;
#end
#implementation DrawPuppetLayer
+(CCScene *) scene
{
// 'scene' is an autorelease object.
CCScene *scene = [CCScene node];
// 'layer' is an autorelease object.
DrawPuppetLayer *layer = [DrawPuppetLayer node];
// add layer as a child to scene
[scene addChild: layer];
// return the scene
return scene;
}
-(id) init
{
if( (self=[super init])) {
// enable events
self.isTouchEnabled = YES;
self.isAccelerometerEnabled = YES;
index = -1;
canvas = [[NSMutableArray alloc] init];
// init physics
[self initPhysics];
[self scheduleUpdate];
}
return self;
}
-(void) draw
{
if([lineDrawing.points count] > 1)
{
for(int i = 0; i<([canvas count]) ;i++)
{
LineDrawing *drawing = (LineDrawing *) [canvas objectAtIndex:i];
for(int j=0;j<[drawing.points count] - 1;j++)
{
LinePoint *firstPoint = (LinePoint *) drawing.points[j];
LinePoint *secondPoint = (LinePoint *) drawing.points[j + 1];
CGPoint point1 = [[CCDirector sharedDirector] convertToGL:CGPointMake(firstPoint.x, firstPoint.y)];
CGPoint point2 = [[CCDirector sharedDirector] convertToGL:CGPointMake(secondPoint.x, secondPoint.y)];
ccDrawLine(point1, point2);
}
}
}
//
// IMPORTANT:
// This is only for debug purposes
// It is recommend to disable it
//
[super draw];
ccGLEnableVertexAttribs( kCCVertexAttribFlag_Position );
kmGLPushMatrix();
world->DrawDebugData();
kmGLPopMatrix();
}
-(void) ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
lineDrawing = [[LineDrawing alloc] init];
lineDrawing.points = [[NSMutableArray alloc] init];
[canvas addObject:lineDrawing];
}
-(void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint point = [touch locationInView: [touch view]];
LinePoint *linePoint = [[LinePoint alloc] init];
linePoint.x = point.x;
linePoint.y = point.y;
[lineDrawing.points addObject:linePoint];
}
- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
//Add a new body/atlas sprite at the touched location
for( UITouch *touch in touches ) {
CGPoint location = [touch locationInView: [touch view]];
location = [[CCDirector sharedDirector] convertToGL: location];
}
}
#end
Can anyone spot my mistake?

Answer 1

Try visiting it all down to a texture, there's going to be a time when your points array gets too large to be drawn nicely
-(void)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
// get the node space location of our touch
CGPoint location = [self getNodeSpaceTouchLocationFromUIEvent:event];
// draw with our current location and a random colour
[_canvas begin]; // our rendertexture instance
// do your drawing here
[_pen drawPenWithPosition:location andColour:_colour];
// end capturing the current pen state
[_canvas end];
}
Here's a simple example project written for iOSDevUK 2012 it uses GL_POINTS in Cocos2d v1 and is based on the approach we took when developing SketchShare