Trivia - why was the decision made to split spec light into reflection and specular?

[joconnell]

Heya Vlado!

For no other reason than trivia, with reflection and spec being the same thing, how come the decision was made in vray to split the two? Was it as support for the older 3ds max fakes or was there usability reasons thought of such as post glows / flares that had it split out into a separate channel?

Cheers!

John

[Alan Iglesias]

Heya Vlado!

For no other reason than trivia, with reflection and spec being the same thing, how come the decision was made in vray to split the two? Was it as support for the older 3ds max fakes or was there usability reasons thought of such as post glows / flares that had it split out into a separate channel?

Cheers!

John

I've had the same question on my mind for years, John. As soon as we had a way to perfectly reflect light sources in a scene it seemed like there was not so much of a need for anything "virtual" specular-wise.

But looking at all the various options you have with the "virtual" specular (like simulating surface properties) and its own native rendering pass you can see how useful it is for many folks - even mostly "in-camera" folks like me!

Getting beginners to understand the difference between the "virtual" specular operations and the more "natural" reflections of light sources in a scene can be a bit of a struggle at times, especially when I see folks wondering why their highlights are so "blown out" or uncontrollable because they are in effect layering two of them on top of each other.

But no big deal really. Just another good tool in the box, right?

Best,

-Alan

[Morbid Angel]

This has come up before. Consider specular and reflection split as means for performance to help speed up rendering. This is probably the main reason why we have specular. From what I remember, consider specular like direct reflection and reflection like indirect reflection. So, when rendered is tracing rays from camera, its not always going to hit every light immediately, especially the small lights in scene. It makes sense in this case to trace the light rays from light into camera since the renderer knows ahead of time about the lights and where they are in the scene etc.

But the same cannot be done for reflection. Since reflection is traced from surface normal, and almost every surface has some form of reflection. This is why specular is fast to render, and reflection is not.

[vlado]

For no other reason than trivia, with reflection and spec being the same thing, how come the decision was made in vray to split the two?

It was very easy to implement and it allowed for some additional creative freedom. For example, for some unfathomable reason, artists often wanted to just boost the "specular" portion without affecting the reflections strength.

However this separation is starting to cause us problems when we want to implement some more sophisticated sampling optimizations for light sources. We are considering merging the reflections and speculars of light sources into one render element (VRayLightReflection or something) for a future version.

Best regards,
Vlado

[PIXELBOX_SRO]

pleas vlado yes merge it it causes loads of confusion in the company
i ve never seen any difference while paying with them really too

[zeronove]

for me that separation is sometimes useful as it allows me to avoid lowering to much the reflection glossiness if rendertime is a priority ...but maybe I'm old school

[Morbid Angel]

for me that separation is sometimes useful as it allows me to avoid lowering to much the reflection glossiness if rendertime is a priority ...but maybe I'm old school

Actually, if you truly want reflection instead of specular, you must uncheck the specular/reflection gloss lock and set specular to 1, in that case only reflection would be traced for all lights (*citation needed from Vlado on actual accurateness of that statement).

Some of my artists prefere to use only reflection and this is what they do.

[Alan Iglesias]

Actually, if you truly want reflection instead of specular, you must uncheck the specular/reflection gloss lock and set specular to 1, in that case only reflection would be traced for all lights (*citation needed from Vlado on actual accurateness of that statement).

Yes, this. The first thing I do with any reflective material is to turn off that Lock button. I only add Specularity if the reflection/highlight I am getting in a "natural" way is not satisfactory.

One of the first things I instruct as well...

-Alan

[Alex_M]

Yes, this. The first thing I do with any reflective material is to turn of that Lock button. I only add Specularity if the reflection/highlight I am getting in a "natural" way is not satisfactory.

One of the first things I instruct as well...

-Alan

Why do you do this, isn't this physically incorrect? To me reflections look the opposite of natural if hglossines and rglossines are not locked together. Am I missing something here and can you explain the benefit of leaving hglossines at 1?

[Alan Iglesias]

Why do you do this, isn't this physically incorrect?

He-he...the age-old question, right?

Yes, if I need to create a specific Specular Highlight with qualities that are absolutely germane to a particular surface type that I am not getting by setting the Reflection Glossiness to match my targeted surface, then yes, this is when I use the Highlight Glossiness function which gives many "virtual" options to affect the specular look.

However, just the simple fact that the Reflection Glossiness control will diffuse any reflection (including in-scene light sources of course, which are by definition, Specular Highlights), in an equal and predictable way, is typically more than enough to "sell" the shots that I typically need to produce. So I always start this way first, adding the HGlossiness later if needed.

These "naturally reflected" Specular Highlights seem to render faster (the renderer is doing less work perhaps) and are not as prone to AA problems sometimes seen when using the Specular Highlight Glossiness function. And I can tell you I have "fixed" more than one rendering over the years where the speculars were "misbehaving" due to both kinds being "stacked" one upon one another.

And rest assured that using the HGlossiness function it is very easy to "blow out" speculars completely out of the realm of the physical!*

*(see Vlado's hilarious comment in message #4 in this very thread!)

I will never, ever claim to know anywhere near as much about a particular rendering's "physical correctness" as Vlado and his most excellent team do, and will always seek to use the ways that their extensive knowledge has been implemented in Vray as much as possible when rendering in 3D. However, I am a fairly observant person (my friends would call that an understatement!) and have a good feel for what looks right and what doesn't.

At the end of the day I suppose, it is up to the artist to decide and up to the client to approve. I consider Vray's HGlossiness tool to be just one of the many fine artist's tools we have to choose from and thank my lucky stars that I have such a fine, well-supported renderer to work with every day!

And, as always, YMMV!

Best to you Alex,

-Alan

[kosso_olli]

I'm not sure, but I think I remember Vlado stating that the rendering equation is incomplete without the specular, and therefore the rendering is incorrect. I agree that unlinking the HGlossines from the RGlossines is most of the time a very bad idea. Maybe that option should be removed.

[Alex_M]

Thanks for the lengthy post, Alan but I still didn't understand why you prefer to work with unlocked reflection and highlight glossiness values in your day-to-day work and if you consider this physically correct. Can you please give me an exact succinct answer? I think that if the Vray developers have made these two glosiness values to be locked then there's a good reason for it. In my tests blurry reflections without specular highlights, as you advocate, look really fake.

Also, check out what the help page of Vray says:

HGlossiness – Highlight glossiness. Determines the shape of the highlight on the material. Normally this parameter is locked to the Reflection glossiness value in order to produce physically accurate results. This parameter can be mapped with a texture in the Maps rollout.

Check this example I quickly rendered and let me know which looks more "natural" to you. Notice especially the completely missing bright sun hotspots that in the real world should be there:

[Alan Iglesias]

Check this example I quickly rendered and let me know which looks more "natural" to you.

Hi Alex,

You are using a Vray Sun/Sky system here, yes?

Absolutely, if you are working with exteriors and would like to create a specular that quickly represents the sun you can (and I have!) use the HGlossiness for these situations.

It can be just fine in some cases of course (yours is very nice!), but more often than not my exterior renderings are using HDRI for IBL as well as the Reflective pass and in these cases the reflection of the sun in the HDRI is usually quite beautiful and realistic. If it is not then I go ahead and either use the HGlossiness or I create a renderable sun stand-in object specifically to create a specular that I am looking for in a particular project. In these cases, the HGlossiness is not used of course.

And when it comes to interiors, well, then specularity is just usually automatic as I typically represent all interior lighting fixtures with a self-lit renderable entity which gives me further control over the specular aspect. And if it isn't working for some reason I have the Hglossiness to use as well!

And as I have said, Your Mileage May Vary which means that anyone might have their own way to approach things. I am merely saying is that this is what works for me and in no way am inferring that anyone else here should necessarily do things in this manner.

I hope this is clear,

-Alan

[Morbid Angel]

Thanks for the lengthy post, Alan but I still didn't understand why you prefer to work with unlocked reflection and highlight glossiness values in your day-to-day work and if you consider this physically correct. Can you please give me an exact succinct answer? I think that if the Vray developers have made these two glosiness values to be locked then there's a good reason for it. In my tests blurry reflections without specular highlights, as you advocate, look really fake.

Also, check out what the help page of Vray says:




Check this example I quickly rendered and let me know which looks more "natural" to you. Notice especially the completely missing bright sun hotspots that in the real world should be there:

[ATTACH=CONFIG]35620[/ATTACH]

Well its what I said earlier. You will not be able to trace sun which is a tiny dot from reflection surface without getting crazy speckle artifacts. Specular imho is just a performance optimization feature.

[Alan Iglesias]

Well its what I said earlier...Specular imho is just a performance optimization feature.

As usual, a very interesting take, Dmitry. Seems that there are a number of opinions regarding the whole Specular thing...

-Alan