whahs the difference tween HDR and IBL lights? in ds and ca
Mistara
Posts: 38,675
do hdr lights make shadow?
i think IBL lights do in poser.
and ibl lights are spheres.
are ibl lights supposed to be 32-bit?
DS can use hdr now? doesn't have to be tif?
is there something to convert tif to hdr?
thanks. :)
Post edited by Mistara on
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Comments
IBL is image-based lighting. Basically that means using an image to provide lighting information for your render.
HDR is an image format. It stands for High Dynamic Range.
Often, IBL that uses HDRs is just referred to as HDR lighting...when in reality, it still is IBL.
IBL lights are not necessarily spheres...that's just one of three common ways of doing it...Cube maps and latlong (latitude/longitude) are the other two...
32-bit maps are better, but not necessary.
No need to convert it. 3Delight handles that at render time (that pause before the render starts when it says "Optimizing x/y images"...that's what it's doing. And really, 3DL has understood hdr formats for quite sometime and auto-converted them.
hdr has more color depths than tif.
doesn't seem to make sense
It makes absolute sense. The "HDR" means "High Dynamic Range". i.e. brighter brights and darker darks. In order to achieve high dynamic range you need more levels of brightness. So, instead of three integer value 8-bit color channels yielding a 24-bit pixel (RGB) as in TIFF, with only 256 levels of brightness for each channel. The various HDR formats use a 16 or 32 bit floating point value color channel for each color with more room for brightness information.
Image formats is an extremely complex subject. Brain strain and neural knots are a risk when considering all the possibilities and limitations.
It makes absolute sense. The "HDR" means "High Dynamic Range". i.e. brighter brights and darker darks. In order to achieve high dynamic range you need more levels of brightness. So, instead of three integer value 8-bit color channels yielding a 24-bit pixel (RGB) as in TIFF, with only 256 levels of brightness for each channel. The various HDR formats use a 16 or 32 bit floating point value color channel for each color with more room for brightness information.
why convert hdr to tif?
i would think hdr be more desirable?
why convert hdr to tif?
i would think hdr be more desirable?
In what situation? A true HDR image in HDR format is far too much information to be represented on paper or on a display. I don't mean the volume of information, I mean the brightness depth information. Few applications are prepared to work with the huge color values of an HDR image. Ink on paper can represent about 7 brightness "zones" where the light intensity of each higher zone is twice the previous one. (Ansel Adams pioneered this terminology with his marvelous b/w photographs). A computer display can manage to represent about 9 zones. An HDR image easily handles 12 to 15 zones. Everything from the black snake in the dark shadow to the sun clearly defined in the brightest of skys.
In order to view that snake/sky image on paper or on a display you need to compress the brightness information from 15 zones to 7 zones. You could keep the information in HDR format but for use by most applications you should convert it to a standard 8-bit color channel-triple system like TIFF. I admit that I don't know if DAZ Studio or Poser can natively handle HDR formats for IBL lighting. I do know that Photoshop can read HDR format images and give you a way to view the extended "zones" by selecting which range of brightnesses you want to see on the display. Photoshop can also apply compression curves to the brightness information to let you attempt to squeeze all the zones down into the viewable 9 or 7 zones and convert the image to a "Tone Mapped HDR Image and store it in TIFF format. If you're not trying to "view" the image then if the application can use the full HDR information to create light then if you the application permits it by separating lighting and image display you can apply the 15 zone HDR image to the lighting mechanism and put the corresponding 7 zone Tone Mapped image or a standard image the visible channels.
and since a true HDR image with say, 15 zones of brightness is capable of representing shadows as well as spotlights distinctly, an HDR image is usually preferred as the lighting source in an IBL lighting situation rather than just a standard 8-bit channel TIFF image. However, technology and mathematics can perform near miracles so it's possible that an 8-bit image could be used to simulate a 15 zone dynamic range by expanding the luminance information at the expense of luminance resolution. But that might be OK for IBL lighting situations whereas the rough luminance jumps might be noticeable if the image were used as a visible image.
Argh..., I think I'm getting a neural knot.
Tiff conversion used to be necessary for earlier versions of DS (and I think they were initially limited to 16bit float.)
I've just checked in the DS runtime and the Uberenvironment tiffs are now all 32bit float.
Though I mostly just use the EXR files from sIBL sets.
poser uses hdr. but not sure if poser is converting .hdr in the firefly render process.
you using exr files with DS? CA?
EXR files directly in DS.
And that's an example that technology moves on! Faster than old people can run. :-(
I surfed the waves of technology for many decades and had a very good ride. Now I just flounder in the whitewash.
And that's an example that technology moves on! Faster than old people can run. :-(
I surfed the waves of technology for many decades and had a very good ride. Now I just flounder in the whitewash.
You're only as old as renderer you feel. :coolsmile: