Yes, I am convinced that IBA::normalize() would be useful to add. 🎣 Mackerel!
(somebody should start by filing an issue so we don't forget about this potential enhancement) On Thu, Jun 8, 2023 at 7:08 PM Vladlen Erium <shaam...@icloud.com> wrote: > Thanx Larry! > > I definitely will check ImageBuf::Iterator. And do my best. > Common or not, but if you'll check some of 3D format parsers, you can find > that they are by default normalize vertices normals. And even if most 3D > DCC apps do the same with normal maps inputs, and most normal maps > generator output normalized data, it still a good to have this function in > openimageio, well, just in case. :D > > Hi, Vlad. > > That's probably the simplest approach with the existing set of IBA > functions, yes. Maybe there is some optimizing you can do around the edges > -- like, `mul(img,img)` may be faster than `pow(img,2.0)`, I'm not sure, > and definitely you want to use the variety of IBA functions that takes a > destination image rather than returning an ImageBuf, in order to minimize > needless buffer copying. But those obvious tricks will only get you so far. > > If you're doing this a lot and it's performance critical, a better way > would be to write it as a single function that uses ImageBuf::Iterator to > traverse the image and do all the operations at once for each pixel, with > no extra buffer copies. Looking at the source code to any of the usual IBA > functions that take one input image and produce one output image will > provide you with a good example to copy and change the guts to make your > new function. > > I don't recall anybody asking for this particular thing before, but if you > think it is a commonly needed operation, then by all means propose a PR to > add this new function after you've implemented it. > > > > On Sun, Jun 4, 2023 at 6:28 PM Vladlen Erium <v...@hdri.xyz> wrote: > >> What should be most efficient way to implement normalizing vector data >> images (normals) using ImageBuffAlgo? >> >> For this moment I only see the way to do this in four steps. >> ImageBuffAlgo::madd for [0.0,1.0] -> [-1.0,1.0] >> ImageBuffAlgo::pow for power of 2 >> ImageBuffAlgo::sum_channels for vector magnitude >> ImageBuffAlgo::div (sec and magnitude) to normalize vector length >> ImageBuffAlgo::madd for normalize to [0.0, 1.0] range. >> >> This not only required to make so many steps but also required a lot of >> temporary buffers, that for huge textures can required lot of memory. When >> all steps can be done per pixel and perfectly parallelized (shaders, cuda). >> >> Maybe I missed some OIIO functions? 🤔 >> >> Best regards: >> Vlad >> >> PS: btw, looks like Google completely filter out all Larry messages if >> Gmail used for subscription to this mailing list. They even not in spam >> folder, where mail list messages quite often can be moved 😒 >> _______________________________________________ >> Oiio-dev mailing list >> Oiio-dev@lists.openimageio.org >> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >> > > > -- > Larry Gritz > l...@imageworks.com > _______________________________________________ > Oiio-dev mailing list > Oiio-dev@lists.openimageio.org > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org > > > > > _______________________________________________ > Oiio-dev mailing list > Oiio-dev@lists.openimageio.org > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org > -- Larry Gritz l...@imageworks.com
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