qt 4.8 with qglviewer (opengl interface) is producing jagged images while some code produces fine images using glut interface

[Manju]

Hello everyone,
I am developing visualization tool using Qt with qglveiwer opengl interface.
I have generated 3 different sets of image using both glut and Qt.
The images produced by glut are fine, but the images generated using Qt show some kind of jagged effect.
I have attached 3 pairs of images. In each pair one image is generated using the glut interface and other image is generated using Qt (qglviewer interface.) The names of images are intuitive to understand.

This problem is highlighted using black colored lines around the area in attached images generated by Qt. The code and logic used for generating both images is same. I have even tried using Qglwidget interface with Qt. But similar problem exists.

I feel interpolation is not happening properly in case of Qt. In case of image pair 3, you can see stripes generated between 2 adjacent rows of quadrilaterals drawn to create a rectangular surface.

The system specifications used are :

Qt version : Qt 4.8.0 (64 bit)
Ubuntu 12.04

1_glut_output.jpg (http://s13.postimg.org/929ay3bon/1_glut_output.jpg)
1_qglviewer_output.jpg = http://s22.postimg.org/qy5c75fzl/1_qglviewer_output.jpg
2_glut_output.jpg = http://s1.postimg.org/wxvwv1gjz/2_glut_output.jpg
2_qglviewer_output.jpg = http://s15.postimg.org/ixpchc3sr/2_qglviewer_output.jpg
3_glut_output.jpg = http://s30.postimg.org/ngmnl6lkx/3_glut_output.jpg
3_qglviewer_output.jpg[link text = http://s24.postimg.org/m09zr1wz9/3_qglviewer_output.jpg