How to draw smooth line in OpenGL with antialiasing?

Question

I need to draw a smooth line in OpenGL and here is what I have done:

glEnable( GL_LINE_SMOOTH );
glEnable( GL_POLYGON_SMOOTH );
glHint( GL_LINE_SMOOTH_HINT, GL_NICEST );
glHint( GL_POLYGON_SMOOTH_HINT, GL_NICEST );
glBegin( GL_LINE_STRIP );
    for( UINT uiPoint = 0; uiPoint < iNumPoints; ++uiPoint )
    {
        const Coord &Node = vecPoints[uiPoint];
        glVertex3f( Node.x, Node.y, Node.z );
    }
glEnd();

What else I can do?

Answer 1

You can generate thin, screen-oriented polygons instead, and set the fragment's alpha according to the distance to the line.

Example :

   a (0,1)                                  b (0,1)
    +--------------------------------------+
  A |                                      | B
----+--------------------------------------+----
    |                                      |  
    +--------------------------------------+
   d (0,0)                                  c (0,0)

Suppose you want to draw segment [AB].

• Draw polygon abcd instead
• Map the UVs (the (0,0) , (0,1))
• bind a 8x1 black and white texture that is white only on the center
• render with a fragment shader that set gl_FragColor.a from the texture

(more or less the technique used in ShaderX5)

But do this only if you can't use MSAA.