[REQ] Sky only EnvMap usage

[Zom-B]

I recently had a idea while playing arround with some high res HDRI for lightning from 3docean.

The thing about the most Sky EnvMaps is that the only use the upper 50% of the image for sky leaving the ground disorted or black.
I request a simple checkbox for exporters to use only the upper 50% of the image("use sky only").
By this we would save 50% of the RAM cost and also have a faster start up of the render.
Since professional EnvMaps are realy huge nowerdays, the saved RAM + Time isn't tiny...

Further thoughts about having a color for the ground part of the croped EnvMaps are maybe usefull, but a pure black replacement (no illumination!). would speed up rendering too, wouldn't it?!

[ENSLAVER]

Good idea. Shouldn't be too hard to crop the environment @ 50% height. I was using a 120mb hdri today, @4xSS it used pretty much all my ram lol

Not sure going further they could implement an option to use a low res version for lighting and/or reflections and a standard res for the background.

Low priority for me really though... I am sure they are working on lots more sexy things ;p

[Zom-B]

Good idea. Shouldn't be too hard to crop the environment @ 50% height. I was using a 120mb hdri today, @4xSS it used pretty much all my ram lol

Yes, exactly what I had in mind with this request. We all have a lot of RAM, but I prefer to use it for multiple Light Layers, higher res or AA etc...

Not sure going further they could implement an option to use a low res version for lighting and/or reflections and a standard res for the background.

I think this only makes sense if you want to have a LDR jpg image used as background, Otherwise you would pay both EnvMaps RAM wise and also rays need to use both, so why don't use the better one only
Smart IBL uses this approach http://www.hdrlabs.com/sibl/index.html
They use a lowres (blurred) HDRI for doing the lightning, a Higher res HDRI for the reflections and a High res LDR jpg for the actually visible background.

[SerNick]

+1 to both ideas.

[CTZn]

I request a simple checkbox for exporters to use only the upper 50% of the image("use sky only").

What would the image ratio be then ?

I don't know how to generate an hemispherical projection... ISL ?

[Frutiger]

What would the image ratio be then ?

I think it'd be something like 4:1 seeing as you'd still want 360 degrees in one direction, but only 90 in the other (lopping off the bottom half).

I don't know how to generate an hemispherical projection... ISL ?

Specialized software is the way to go. Alot of people use Hugin. There's also a program called panotools that works pretty well. I'm not sure if Indigo Shader Language would be able to do that for you.

[CTZn]

I'm not sure if Indigo Shader Language would be able to do that for you.

Me neither, but mapping a custom sphere, one could emit black if the world space normal is pointing up. However replacing native Indigo methods by custom ones will always impact performances negatively, furthermore when ISL is involved.

[Zom-B]

Me neither, but mapping a custom sphere, one could emit black if the world space normal is pointing up. However replacing native Indigo methods by custom ones will always impact performances negatively, furthermore when ISL is involved.

I also think that Indigo used quite some optimizations regarding EnvMap sampling, calculation and witchcraft. You'll drop these benefits using a handmade mesh based solution...