Sttencil Buffer Shadow Overlapping

If i have more than a single one point light, how to create real-visible effect of the shadow overlapping? I suppose using glBlendFunc() but dunno how.Please help!

You do a multipass solution:

For each light:

  1. Clear the stencil buffer
  2. Create a stencil mask from light ā€˜nā€™
  3. Add the light from light ā€˜nā€™ to the unmasked regions.