Re: [Mesa3d-dev] HELP! with stencil... :)

[Brian P. <br...@pr...>]

io...@cr... wrote:
> 
> Hi everybody!
> 
> I'm doing this question in this list because nobody else could
> answer me in a way I can understand it.  Sorry if this is off-
> topic, but my project REALLY needs an answer to this question.
> Hope you, Brian, or any other GL expert, can finally tell me
> about it.
> 
> What happens to a stencil index value in the stencil buffer
> when I specify GL_INCR or GL_DECR as the stencil operations
> to do with glStencilOp() for any of the stencil tests, if I
> call glStencilMask() with a mask value different than all 1's?
> Does the stencil index gets just incremented/decremented? Or
> the value is gathered, incremented/decremented, and then masked
> to be written again to the stencil buffer?

The later, I believe.  In pseudo-code:

	Read stencil value, call it v.
	Apply stencil op to v, such as increment/decrement.
	Write v to the stencil buffer with write masking.

Masking is only applied upon writes.

-Brian