Qt + OpenGL rendering MetaBall using Raytracing -- 2

Hi, I have an example of rendering a number of spheres using raytracing (Qt nad QOpenGL). I want to edit the code to render the spheres as a Metaball (connected ball) with smooth surfaces. See the images: The first image represents the spheres. They seem connected but in fact, their surface is disconnected surface. The second images (step 2 and 3) shows a metaball. What exactly I want is that making all the balls appear connected like step 2 in the second image. Here you can find an example of the metaball. [login to view URL]