Are HDRIs faster rendering?

AndyS

Hi,

just curios:
Are HDRIs speeding up render compared to conventional environment settings?
How is "HDRI Daylight Clean Skies" compared to "Sun-Sky only", for example?

Is there even a chance for a meaningful statement?

My personal impression, using some of the HDRIs out of the TerraDome-3 product, the HDRIs need longer to render. At least on my i5 CPU-only Win7 PC.
But we all know it can dramatically depend on the camera perspectives. In the same set only a little different camera position caused over 40% more render time due to the different angle it looked on an indrectly lighted area to get rid off those awefull gainyness on the skin.

Serene Night

I find sun-sky render  faster than hdri for me.

xyer0

I can't say generally, because I almost always use an hdri, but I can say that the UltraHD line of hdri's appear to cause a scene to render noticeably faster than other hdri's. This is not scientific, however. And the lighting of UltraHD is also crisper and more pleasing to my eye.

AndyS

OK,

but those HDRIs do have a general problem:
Shadows of your characters are not correctly transferred to the "structures" of the environment. I already noticed it in the promos of a different HDRI product.

Faster rendering of cause! Because you don't have any additional props to build a detailed environment. So the absence of additional complex structures saves the time to render it (and a lot of memory).

RobotHeadArt

HDRIs are basically images so they need to be loaded into memory much like a texture map.  Different HDRIs are made at different resolutions and with different lighting baked in so it's probably hard to make a general statement about their speed.  Indirect lighting is always going to be slower than direct lighting.

Richard Haseltine

If you want plausible ground shadows you need a mesh of the right shape to act as a shdow catcher, which can be done by making it a Matte object via the advanced iray node properties script in Script>Utilities.

AndyS

Yes, of cause, well known.

But you have to try to adjust the geometry almost fitting to the background/underground structure.
And it is every time depending on the new camera position (if you do shots from different points of view in one set).

That's why I prefer a real environment.

Mattymanx

They can render faster.  Their main bennefit is that you have a complete environment for your scene which will show up in reflections.

AndyS

Yea, agreed,

but ...
Only faster because of the not additional objects to be rendered too.
And the rest - Please read above. -> no really complete environment

cdpro_2831bbd990

You can use an HDRI environment of say, a forest, as you background, and a few detailed trees and structures in the foreground.  The HDRI will provide matching lighting for the environment and will fill the scene with sky and distant horizon.  The select models of trees and other props will provide the up close environment, allowing easier interaction with your figure.  Using an HDRI for the big fill in background takes up much less memory that a whole bunch of detailed models.

AndyS

Yes, you can do.
As far as the picture fits to the topic of your scene. Otherwise you can only arrange scenes depending on the HDRI products you purchased.
But as you could read above, there're some problems to be solved.

The original question was, whether the pure clear sky HDRIs render faster compard to the sun-sky only setting.
And with sun-sky only you are free to position the sun regarding inclination, azimut and season.