Selection mode and Stencil buffer

OpenGL OpenGL: Advanced Coding
1

Hi, the opengl manual says that “in selection mode, no fragments are rendered into the framebuffer”.
What does “rendered” mean :

  1. The polygon is rasterized into fragments, per-fragment tests are done (as usual), but no pixels are commited to the (color) framebuffer ?
  2. The polygon is not rasterized at all, no fragments are generated and nothing is written into the framebuffer.

The reason I am asking all this is that I want to be able to select polygons inside a bitmap region (using the Stencil buffer). Does anybody have any ideas?

If (1) is true, then is it hardware-accelerated, or is it just a trick the software layer (OpenGL), above the 3d-hardware driver, does with the stencil buffer to find which polys are actually written?

Thanks in advance…

2

(2) is true.
2. The polygon is not rasterized at all, no fragments are generated and nothing is written into the framebuffer.

Selection