Corona Renderer Forum

General Category => General Discussion => Topic started by: cjwidd on 2019-04-11, 23:20:32

Title: [RESOLVED] Why is HDRI lighting so effective?
Post by: cjwidd on 2019-04-11, 23:20:32
Why is HDRI lighting so effective?

As a 3d artist without formal training, my approach to lighting has mostly been a process of trial and error. On the other hand, I suspect that 3d production houses have a much more constrained approach to lighting that involves some best practices for lighting certain types of scenes, e.g. interior vs. exterior, product vs. characters, etc.

Despite the fact that I will often experiment with different combinations of physical lights, bounce cards, sunlight, (etc.) during the initial lighting pass, there is some major proportion of scenes that I will ultimately light with only an HDRI, often because it simply looks better and renders faster. After reading dozens of blogs from Corona, Bertrand Benoit, and others, it seems that HDRI (only) lighting is fairly common, and if additional light sources are included, it is mostly to enhance a particular highlight, or fill a dark patch.

At the very least I would curious to know if HDRI renders faster in Corona than physical lights.
Title: Re: Why is HDRI lighting so effective?
Post by: TomG on 2019-04-12, 12:52:31
I'd say HDRI lighting is effective because "that's the way the real world works" - in that there is light coming from all around, from the sky and surrounding environment. The two things are that using an HDRI simulates this as the first thing and that it includes things like trees, buildings, and ground to simulate reflected/bounced light from those; and the second is that because the way HDRIs work is a known quantity, it can be sampled effectively (compared to early approaches such as "create a dome of lights to pretend to be a sky sending light from all directions"). And the third that I just thought of is that it also adds realistic reflections, which a dome of lights does not.
Title: Re: Why is HDRI lighting so effective?
Post by: maru on 2019-04-12, 12:57:06
I am really not sure how to understand this thread. Generally something renders efficiently in a render engine, because it is designed to be efficient, or because it's a simple effect which is not expected to render slowly ever. :)

At the very least I would curious to know if HDRI renders faster in Corona than physical lights.
Again not sure how to understand this.

One Corona Light and one simple object will render quickly (meaning no noise in a short time).
HDRI and one simple object will render quickly too.

One Corona Light in a complex scene can render for ages.
HDRI in a simple scene can render for ages.
Title: Re: Why is HDRI lighting so effective?
Post by: Juraj on 2019-04-12, 13:20:09
Lot of people also use only single HDRi because they are lazy ;- ). Sometimes throwing simple light into space creates something magical straight away so the only choice is to decide what that light is. Other times, light needs to be shaped and I see many photographers being lot more proficient in this than Archviz guys who expect results without work, waiting for single magical HDRi to sort all their needs.

After 8 years, I still learn something new about light almost every single day, endlessly frustrating (almost painful sometimes) and rewarding experience at same time.
Title: Re: Why is HDRI lighting so effective?
Post by: maru on 2019-04-12, 13:50:38
After 8 years, I still learn something new about light almost every single day, endlessly frustrating (almost painful sometimes) and rewarding experience at same time.
With possibility to load multiple HDRIs and suns into LightMix and caustics, both coming soon, you will probably have to face a new wave of frustration and rewarding experience. :D
Title: Re: Why is HDRI lighting so effective?
Post by: Juraj on 2019-04-12, 13:54:20
After brief experimentation, I somewhat forgot LightMix exists (IR with denoise is decently fast previewer on its own). I need to get back into it.
Title: Re: Why is HDRI lighting so effective?
Post by: jms.lwly on 2019-04-12, 14:03:32
With possibility to load multiple HDRIs and suns into LightMix and caustics, both coming soon, you will probably have to face a new wave of frustration and rewarding experience. :D

*picks up jaw from floor*

Sounds amazing!
Title: Re: Why is HDRI lighting so effective?
Post by: actrask on 2019-04-12, 19:18:34
Quote
I still learn something new about light almost every single day, endlessly frustrating (almost painful sometimes) and rewarding experience at same time.

^^^
Title: Re: Why is HDRI lighting so effective?
Post by: cjwidd on 2019-04-12, 21:25:57
Maru, I understand your reaction, because on the face of it the post appears somewhat empty. However, I am asking about efficiency from a graphics implementation perspective. I understand that Render Legion is not obligated to share intimate details about how their software works, but I would be curious to read about technical details of the Corona renderer if they became available.