Pros and Cons of using HDRI domes for global illumination

#1

Im looking for a list of Pro’s and Con’s for using HDRI domes for global illumination.
Is it better than everything else, and in what way is it not better?
Iv googled “Pro’s and Con’s for using HDRI domes for global illumination” but found nothing that is close to what i need

#2

Im a bit confused by the question, a HDRI is just an image with mulitple exposures.

The technical equivilient is a sky environment - except a sky environment is usually linked to a 3D light (direct light/sun) as well. Both are good, depending on your needs.

The artistic equivilent is having a scene full of ‘things’ which reflect, bounce light, give light etc…

Examples:

  1. You take a photo in your backyard, you want the reflections, time of day and lighting to appear like the photo. It would be a good idea to also take a spherical HDRI at the same time so the lighting/reflections match.

  2. You want to match a particular style, color, time of day that suits the HDRI, and/or use the lighting as direct light instead of a 3D light.

  3. No HDRI- using a Sun/Sky instead or Studio Lighting, or whatever it is you are looking to achieve this can be created entirely in 3D instead of using a HDRI. It doesnt make a difference as long as you get the output required for the project.

#3

Yes i suppose some background information will help.
I work for a company that has its own in house interior design software that we sell.
Currently we use the sky environment solution i believe, for our global illumination, but its poorly optimized, and Developers are not keen to work on it.
After a workshop we decided to look into using a dome for global illumination, but our developers are asking what the end goal is. So i want to use the pro’s and con’s list as part of the motivation.

#4

I think this is a good question.

If the goal is to have better looking renders then its not going to change much, a HDRI is not a magic solution that makes things look more realistic. Lots of high end product renders, architectural renderings etc just use a sun/sky, or just a direct light with no need for a HDRI, its just another tool in the box.

It could actually do the opposite if you need consistency with previous renders you have done, matching them or updating old work could be a pain if you havent taken the time to ensure your assets look good in multiple lighting situations. For example using a direct white light is easy for architecture because clients can see the color of the timber, steel, fabric etc as intended, when using a physical sky you introduce kelvin temperature which is a fairly simple variable to offset (white balance), but this one variable can introduce headaches for consistency if you are not careful. Now lets introduce a HDRI, which casts many colors from the image such as the example below from HDRI haven. Now all of a sudden you have this rainbow fabric or the overhead lights appearing in some reflections and the client is asking “why is that there, can you photoshop that bit out” etc.

hdri
hdri.jpg1492x850 179 KB

The best way to conduct your test IMO would be take one of your current scenes, light it with a HDRI and then compare the results. If your heading in a better direction than where you are now then you can write a pro/con list from the outcome. Otherwise without a comparison for your specific situation its like telling your team we should be eating bananas instead of apples for lunch, I hear they are better for you.

#5

Thank you for all the assistance. It would definitely seem that both aspects have their own advantages.
The reason we are looking at using the dome is to create an immersive effect when our clients do virtual walk through of their designs. At the moment we have static images on the windows, and light is fed through these images. So what ends up happening most of the time is the outside can be SUPER bright in the renders.
Also the static images are really low res at the moment, max is sitting at 480p i believe. It would seem there is a lot to be considered when approaching this topic.

#6

If I understand you correctly, what you are saying is you want to have a ‘dome’ around your scene so when you see outside the windows you see an environment, instead of an image stuck to the window?

If thats the case a simple solution would be creating a hemisphere around your scene, map an environment texture onto it and give it an illumination material so its at the desired exposure. This should fix the low resolution images on the windows and the brightness problem as well as create some depth (these 3 variables would go into your Pro/Con list as a Pro).

The image you place on the hemisphere dome can be a HDRI, or any equirectangular panorama image that suits. Note the HDRI doesnt have to be used to illuminate the scene, it can just be used for the visual effect (another Pro for the list as it doesnt effect your lighting workflow). At a later point you can always think about introducing a lighting change if you are still not happy with the results, or want some influence from the exterior lighting - would require thorough testing however.

#7

Wow! Okay that sounds like really great suggestion.
Would you mind if i quoted you in some aspects of your comment when i reply to the developers.
I think having the correct usage of words strung together will make for a more compelling argument.

Again thank you for the assistance.

#8

Sure thing, glad I could help.