glStencilFunc(GL_NEVER, 0, 0) still renders?

Question

I have problems utilizing the stencil buffer, and it's seems to boil down to not work at all. Given the following code:

  glEnable(GL_STENCIL_TEST);
  glClearStencil(0);
  glClear(GL_STENCIL_BUFFER_BIT | GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glColor4f(1, 1, 1, 1);
  glStencilFuncSeparate(GL_FRONT_AND_BACK, GL_NEVER, 0, 0);
  glStencilOpSeparate(GL_FRONT_AND_BACK, GL_INCR, GL_INCR, GL_INCR);
  glBegin(GL_TRIANGLES);
  { draw something }
  glEnd();

The triangles are still drawn!? Am I missing something trivial here?

Note: I'm not rendering to a frame buffer, I'm using glStencil...Separate just to make sure it's not related to front\back, I've kept bits of code that to me doesn't seem related.

"*I'm not rendering to a frame buffer*" Then what are you rendering to? — Nicol Bolas, Nov 20 '12 at 17:59
What I mean is, I am rendering directly to the screen, ie no framebuffer objects are activated. — Viktor Sehr, Nov 20 '12 at 17:59
@NicolBolas: They are cleared (updated the code, and retested) — Viktor Sehr, Nov 20 '12 at 18:02

score 3 · Accepted Answer · answered Nov 20 '12 at 18:08

3

You don't have a stencil buffer. And by the specification (from 4.3 core, folio page 432):

If there is no stencil buffer, no stencil modification can occur, and it is as if the stencil tests always pass, regardless of any calls to StencilFunc.

answered Nov 20 '12 at 18:08

Nicol Bolas

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You mean I have to render to a frame buffer object with a stencil buffer attached? – Viktor Sehr Nov 20 '12 at 19:19
@ViktorSehr: No; you have to ensure that whatever framebuffer you use has a stencil buffer. If you're rendering to an FBO, then that means you need to use a packed depth/stencil buffer. If you're rendering to the default framebuffer, then you need to use a pixel format that provides a stencil buffer. That's platform-specific, so unless you mention how you're creating your context, I can't really help. Also note that "framebuffer" is *one word*, not two. – Nicol Bolas Nov 20 '12 at 19:40
Seems I didn't provide a stencil buffer to the default-\screen frame(no space)buffer. Thanks! – Viktor Sehr Nov 21 '12 at 15:20

glStencilFunc(GL_NEVER, 0, 0) still renders?

1 Answers1