Question

There is this site…

… where they explain how to draw an antialiased line.

Exactly what I want!
but…

I don’t understand how to achieve that for a simple line. I have found the online version of the book (the article is kind of derived from the book), i have downloaded the sample code (showing a stick figure doing fancy moves), but there is so much mambojambo going on… some strange python script… circles as png-images and as header files, almost everything is written in cpp, files i copy to my project produce lots of errors that i can’t resolve properly and so on and so on. And I think I don’t need all of that fancy stuff, since I only want to draw lines in a simple cocos2d based app [Btw…. I didn’t want to use AA, but my lines are thicker than 5px which makes them have ugly holes when connected (f.e. in a circle made of several lines) so that I must use AA as it seems].

So does someone have or found a tiny little piece of runnable sample code using the principle explained in the linked article ?

---

Notes:

1. In the picture you see the holes:
   http://pimml.de/circles.png

2. Here you will find the code of the mentioned stickman (AA Lines): http://examples.oreilly.com/9780596804831/readme.html#AaLines

3. This is how I draw my circles:

   int segments = 80;
   CGFloat width = 100;
   CGFloat height = 100;
   CGPoint center = ccp(800,200);  
   
   glDisable(GL_TEXTURE_2D);
   glDisableClientState(GL_TEXTURE_COORD_ARRAY);
   glDisableClientState(GL_COLOR_ARRAY);
   //glEnable(GL_LINE_SMOOTH); // doesn't work on device
   glTranslatef(center.x, center.y, 0.0);
   glLineWidth(3.0f);
   GLfloat vertices[segments*2];
   int count=0;
   for (GLfloat i = 0; i < 360.0f; i+=(360.0f/segments))
   {
       vertices[count++] = (cos(degreesToRadian(i))*width);
       vertices[count++] = (sin(degreesToRadian(i))*height);
   }
   glVertexPointer (2, GL_FLOAT , 0, vertices); 
   glDrawArrays (GL_LINE_LOOP, 0, segments);
   
   glEnableClientState(GL_COLOR_ARRAY);
   glEnableClientState(GL_TEXTURE_COORD_ARRAY);
   glEnable(GL_TEXTURE_2D);    
   

Answer 1

I ran into that issue as well. I spent a while figuring this out… I used a solution similar to this one for a while (via walterBenjamin on Apple.com):

https://devforums.apple.com/message/264670

This works, it is easy and it looks nice, but it still isn’t the best (for what I am doing). In the end, I wrote my own solution that combined GL Paint particle drawing with his solution of point-to-point line drawing.

I made an array and at touchesBegin, touchesMoved, I added a point to it:

[currentStroke addObject:[NSValue valueWithCGPoint:point]]

Then I iterate through the strokes, such as you see in GL Paint using GL_Points.