I better explain more over the issues of designing the user interface. I have already had the opengl scene as an underlay and i am trying to have the UI grouped into a translucent (opacity : 0.1) and rounded rectangle.

I want to have two sliders along with two text items well-aligned in a grid-layout and stuffed inside the translucent rectangle. Initially i had all the items inside the rectangle and i found that the transparentcy that is applied to the rectangle is also applied to all the of the children. This is not what i wanted. Then i was suggested that i should put the items(Text, and Slider) as siblings instead of children. Now how should I align the grid layout with the rectangle so that it moves along with the rectangle ?