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Stencil buffer, the inner workings?

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I'm a bit confused regarding how the stencil buffer works. I know the basic stuff but I'm a bit uncertain how the different masks are applied. Consider: D3DRS_STENCILPASS = D3DSTENCILOP_INCR D3DRS_STENCILWRITEMASK = 0xf0 I'd be under the impression that the gpu would perform: X = (X + 1) & 0xf0, right? This means that the content of the buffer will never change? Another question, about D3DRS_STENCILMASK, the docs states "Mask applied to the reference value and each stencil buffer entry to determine the significant bits for the stencil test." Does the gpu perform (X & 0xf0) op D3DRS_STENCILREF? So: D3DRS_STENCILMASK = 0xf0 D3DRS_STENCILFUNC = D3DCMP_GREATER So for all X < 0x10 the stencil test will fail, or? Can someone shed any light on the eaxact behaviour, or a link?

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Ahh.. found the following in the docs:

Quote:

performed using the following steps.

1 Perform a bitwise AND operation of the stencil reference value with the stencil mask.
2 Perform a bitwise AND operation of the stencil buffer value for the current pixel with the stencil mask.
3 Compare the result of step 1 to the result of step 2, using the comparison function.

These steps are shown in the following code example:

(StencilRef & StencilMask) CompFunc (StencilBufferValue & StencilMask)

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