Z-Buffer FAQ?

[Quitch]

So, what is the downside of all this additional precision? Larger memory hit? Takes more bandwidth?

 

[Cryect]

Basically, and really you definately don't want to be using 16 bit Z-Precision anymore (well unless you are messing around with something that is really low poly count where as well the polys aren't close together).

 

[Quitch]

Okay, but say then 24bit compared to 24bit 8bit. What's the up and down sides to going with the additional 8bit stencil over plain old 24bit?

 

[Cryect]

Heh as far as I know just that you get a stencil buffer. Either way you have to read you data 32 bits at a time. It could be possible those 8 bits really get used in some other way to help performance but I don't know. Also not sure on this but it might be easier to do Z-Buffer compression when you don't have stencil bits since thats 8 less bits you have to worry about trying to compress.

 

[KimB]

The stencil buffer is a programmer's tool. It's not related directly to turning on any performance or effects.

 

[Mendel]

The stencil buffer is a programmer's tool. It's not related directly to turning on any performance or effects.

So even if I select a mode in radlinker, where there is not this 8 bit stencil listed, I will still get stencil shadows when game requests such a thing?

 

[Simon F]

Okay, but say then 24bit compared to 24bit 8bit. What's the up and down sides to going with the additional 8bit stencil over plain old 24bit?

I think it's likely that you'll find that, in the above cases, if you haven't enabled the stencil, the 24 bit Z data will still be put into 32bit units and the remaining 8 bits ignored. Its the same with 24bit colour.

 

[KimB]

The stencil buffer is a programmer's tool. It's not related directly to turning on any performance or effects.

So even if I select a mode in radlinker, where there is not this 8 bit stencil listed, I will still get stencil shadows when game requests such a thing?

I don't think the game would be able to run its stencil algorithm if the stencil buffer is disabled, no.

 

[Quitch]

From what I can gather, there seems little point in selecting anything other than 16,24,8bit stencil?