Hello Constantin,
Constantin Müller wrote:
>>> I'm wondering if nobody ever did a readback of the Stencilbuffer, or
>> it's quite possible, since the stencil is usually only needed when
>> trying to achieve a specific effect and even then readback is often not
>> required - for performance reason most people will usually try quite
>> hard to leave the data on the GPU only ;)
>>
>
> how can I get access to the stencil data from the image?
> I got the packed depth/stencil image, but how can I readout the stencil data?
> Is there any functionality available for that?
as far as i understand it the stencil data should be in one of the four
bytes that make up every pixel in the image. Calling img->getPixel(i)
you can access the individual bytes:
UInt32 stencilByte = 0;
for(UInt32 h = 0; h < img->getHeight(); ++h)
{
for(UInt32 w = 0; w < img->getWidth(); ++w)
{
UInt8 p = img->getPixel(stencilByte + 4 * w + (h * img->getWidth()
* 4));
}
}
I don't know in which of the four bytes the GPUs store the stencil
value, but changing stencilByte between 0..3 you can try them all.
Cheers,
Carsten
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