How to plot a point or small sphere onto a TH3D drawing with OpenGL?

With openGL, i would like to superpose the picture of a point (or a small sphere) at some coordinate (x,y,z)
with an iso-surface of a function previously drawn by TH3D::Draw(“gliso”) .
I tried many things using tutorials, but with no success.
(my objective is to see a point moving on a surface :smiley: )
Thanks in advance,

Have a look at $ROOTSYS/tutorials/eve/glplot.C and similar examples. Other than combining objects in Eve/Gl-viewer - it’s not possible, gliso in a pad is gliso and it knows nothing but surface data.