Is the stencil buffer still relevant in modern OpenGL?

Question

Me and a friend have been having an ongoing argument about the stencil buffer. In short I haven't been able to find a situation where the stencil buffer would provide any advantage over the programmable pipeline tools in OpenGL 3.2+. Are there any uses to the stencil buffer in modern OpenGL?

[EDIT]

Thanks everyone for all the inputs on the subject.

Answer 1

It is more useful than ever since you can sample stencil index textures from fragment shaders. It should not even be argued that the stencil buffer is not part of the programmable pipeline.

The depth buffer is used for simple pass/fail fragment rejection, which the stencil buffer can also do as suggested in comments. However, the stencil buffer can also accumulate information about test results over multiple passes. All sorts of logic and counting applications exist such as measuring a scene's depth complexity, constructive solid geometry, etc.

Answer 2

To add a recent example to Andon's answer, GTA V uses the stencil buffer kinda like an ID buffer to mark the player character, cars, vegetation etc.

It subsequently uses the stencil buffer to e.g. apply subsurface scattering only to the character or exclude him from motion blur.

See the GTA V Graphics Study (highly recommended, it's a great read!)

Edit: sure you can do this in software. But you can do rasterization or tessellation in software just as well... In the end it's about performance I guess. With depth24stencil8 you have a nice hardware-supported format, and the stencil test is most likely faster then doing discards in the fragment shader.