The output format depends on both hardware and the context the
rendering is done in. If you have an intel GPU (i.e. macbook or mac
mini), you're stuck with 8bit integer because that's all the hardware
supports (this caused much head scratching for me last week), older
cards won't support 16/32bit float too but anything recent from ati or
nvidia will do it.
The next thing is the context: I think QC runs in an 8bit integer
context, so that's what you'll get from CI (it would be very slow if
it ran in 128bit (which actually means 32bit float, 4 (for rgba) x32 =
128) all the time when you're only targeting an 8bit render.
You can force 16/32bit float processing with a render in image - send
what you're doing to a billboard inside a render in image and set it
to 16/32bit and your processing will be done at that precision. 32bit
tends to be a lot slower than 16bit, and you lose things like
filtering which might be important, so 16bit is better if it's
accurate enough.
Chris
On 16 Oct 2008, at 20:53, Greg Best wrote:
I think I'm finally zeroing in on the causes of my headaches-- it
looks like the image that CI is spitting back to me is using 8 bit
floats. Actually, I think they're 8 bit fixed point values because
I'm limited to the range of [0,1]. My Core Image patch won't give
me an image back with any value less than 0.00392 (which is about
1/255).
0.002 gets rounded up to 0.00392, and dividing that number in half
gives me zero.
The Core Image docs say it treats everything like 128bit floats, so
am I facing a hardware limitation or a QC limitation? Is there
anyway to get more resolution?
Thanks--
Greg
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