Why visual effects artists love this shiny ball
evacyn
Posts: 961
in The Commons
Just wanted to share this interesting video from Vox on the use of HDRIs. Nothing groundbreaking, but it gives a history and the different ways it's being used:
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..interesting. The issue I have with most HDRIs though is the sun is often slightly dimmer than the Iray Sun.
Here are two rednerings of the exact same scene using the same render settings. In the first one I used the Iray Sun/Sky (employing the Sun Chain as I didn't want to mess around with the, time date,and location settings). The second sample used an HDRI Notice how the HDRI "sun" seems to have a lower luminosity than the Iray "sun" even though the exact same tone mapping settings were used.. Also in the HDR image the girl's shaodw is sharp edges and darker while it has more of a "cool" lighting temperature, whereas with the Iray sun, the edges are more diffuse and the colours appear more natural. The HDRI i part of a commercially purchased set, not a freebie.
Kyoto kid, unless I'm missing something here I'm not sure why you would expect two different light sources to have the same properties as each other, regardless of the same tone mapping and render setting. I would expect them to be different.
HDRi and 360 Panorama are not always the same thing though,
I was using IBL lighting in Carrara and Poser before I even knew what a HDR was, what I did use was 360 spherical renders
which incidently don't work well in iray which needs high dynamic range
...the Iray sun/sky setting is supposed to faithfully represent natural sunlight.. The only downside, is I only get a clear blue sky so to have any cloud or other atmospheric definition requires using an HDRI .A while ago I purchased the Cloudscape Creator bundle figuring I could finally get cloud planes and individual clouds to use with the Iray Sun/Sky setting, but I discovered they also include an HDRI sky and sun as well that also seems dimmer.
This is where I am having difficulties with the "realism" as when I change the tone mapping settings to match the luminance of the Iray Sun the scene begins to look washed out (and the shadows still unnatural). The issue with IRay is you cannot just use the skydome and it's GI lighting as the dome blocks out the Iray Sun. In 3DL you can use a distant light and turn shadows off for the dome (which is what I did for the scene below). This uses one of the HDRIs from the same set in the image above, and IBL Master for 3DL in place of the UE component for the HDRI to reduce render time along with AoA's Advanced Distant Light. for the sun at 100% with shadow softness adjusted to 90%. The shadow quality of an HDRI sun is fixed and cannot be changed, neither can the luminance Only the total environment lighting can be adjusted (Sun and GI).
This looks like what happens when you use a non-HDR image as a sphere. Is the image you are using as a sphere actually high dynamic range? That would explain these results. It's possibly a normal image saved in an HDR format, but without actually having a high dynamic range.
...yes, the HDRI I used in the second image is a full sphere with sun (IBL Skies). Everything else in the scene is geometry. This is still a WIP as I was going to remove some of the background flora to reduce render time until I saw that the HDRI's sun wasn't as lumimous and warm as the Iray Sun/Sky and the edges of shadows were too sharp. The product page mentions the HDRIs are High Dynamic Range Environment images and they were released in late September, 2017 so they should work for Iray.
I rarely use HDRIs with foreground scenery and a ground plane (except when reflections in interior scenes are needed) as there is no displacement or bump for the ground plane, (particularly in outdoor scenes).