Basically the help for HDRI in the SW Help is to say that you
can use hdr images.
So my first question is this. Is just the presence of a HDR image selected as the scene environment required to activate the HDRI based lighting or is there some other settings needed.
Secondly, after a quick web search on HDRI or HDRR I could not find a simple explanation of how MentalRay or other render engines actually calculated the light direction and other properties from the HDR image. Most of what I found had to deal with range of contrast and the clarity of really dark or really bright objects, but not the calculations of the light direction, etc. Do any of you have a link handy that could explain it? I'd really appreciate it.
Thanks.
So my first question is this. Is just the presence of a HDR image selected as the scene environment required to activate the HDRI based lighting or is there some other settings needed.
Secondly, after a quick web search on HDRI or HDRR I could not find a simple explanation of how MentalRay or other render engines actually calculated the light direction and other properties from the HDR image. Most of what I found had to deal with range of contrast and the clarity of really dark or really bright objects, but not the calculations of the light direction, etc. Do any of you have a link handy that could explain it? I'd really appreciate it.
Thanks.
In addition to having an HDRI image, you need to make sure Indirect Illumination is on (but it should be on by defualt .) If you turn all other lights off, including ambient, you should be able to light your scene from the HDRI environment by itself.
HDR images incorporate "Tone Mapping" and are a special image type that have values beyond the normal RGB ranges. HDR images have "power intensities" (sorry for lack of a better word) in areas of the image that are beyond just, say 100, but more in the 10 to 20 thousand percent range over other parts of the image. Rendering programs can take advantage of these images in a spherical environment to actual emit light into the scene. Please note that PW does not require HDR images in the environment tab, but can use regular images, yet the effect is greatly increase when they are HDR.