Vray light Affect specular vs Affect reflections

[dominikmateasik]

Hello,

ive come around this issue that doesnt make much sense to me

 

what is the exact difference(physically explained if possible) between the Affect specular and Affect reflections in vray light options.If i got it right,in real world, reflection is divided into two types 1.specular reflection(reflection from mirror-like surface) and 2.diffuse reflection(scattered reflection from rougher surfaces)

 

in vray though,these rules seem not be applied as whether i uncheck one or another on mirror like or rough surface the result is always same- the affect reflection option alone has always greater influence on light reflecting from the surface than affect specular option ticked alone

 

id like to understand this effect so if have any explanation thank u very much in advance:)

[Francisco Penaloza]

From what I understand, this check box the only function that have is to specify if the light affect specular or reflections rays on the materials.

So if you un-check one of them Light turn invisible for that channel. Of course if you object is perfect reflective with VRay you won't see much changes, but if you object has blurriness then you'll see the changes.

Now talking about physically correct, you need to understand that this software are designed to be as flexible is possible for high productions environment, so acting only under physical rules it does not apply, this does not mean that the whole theory under VRay is imaginary, it is pretty accurate, but with the advance of technology different approach need to be taken to mimic physical behaviors and be able to bend them or adjust to the artist desire.

[dominikmateasik]

thanks for reply,my next question follows though,maybe too primitive of me asking this but what is the specular and reflective channel then,does specularity consist of highlights and reflection of overall reflection of material?

[notamondayfan]

A specular highlight is where the light source is seen in the reflection of the object. ie the sun reflecting onto a metal building will be seen in the specular pass, but the sky and environment will be seen in the reflection pass. If you didn't want the sun "flaring" on the building side, you would untick "affect specular" and the sun wouldn't appear in the specular pass.

 

Dean

[dominikmateasik]

thanks! so basically specular pass is only for "light energy" to show on the object reflecting it? that means if i have a vray light as an rectanlge object radiating light from itself and uncheck affect specular i should see,on the reflecting surface, only a rectangle with really white colour as an Affect reflection is on alone but no highlights made of the light energy

[notamondayfan]

Yes I think that's how it works, you would see the white rectangle in the reflection. I'm a bit rusty on the exact science!

 

The only time I really use the affect spec and affect reflection though is when the specular is either too high and I need to fake it, or if the specular is appearing in a bad location, so I would copy the light, move it and have 1 for the light and reflection, and another purely just for the specular.

 

Dean

[dominikmateasik]

thank you Dean very much,this was very helpfull,now i know whats what:)

[Francisco Penaloza]

Sorry maybe the work channel was not the right one in this case, but what I meant is those check boxes only affect that effect or property, so as mentioned here, if you have a shinny metal with a rectangular light, un-checking this boxes, it will make the light invisible in that specific property.

You can only see the light as rectangle,(reflections) or only see the light as a blurry almost rectangular shape(depending of intensity) or you can not see it at all.

If you have a big interior scene with very reflective floors and maybe reflective walls, full of glasses and so on, this can be a ray tracing nightmare, so if your machine just can't render on time, you can turn off glossy and reflection visibility on some lights, and this will reduce your render time.

Well this may not sound right for some "purist real life setup" artist, but you gotta do what you can to meet your deadline right?

[Tommy L]

I real life there is only one kind of reflection.

In CGI its split into two, reflection and specularity, just so you can control the highlight. The high light is the reflection of light sources.

[dominikmateasik]

I real life there is only one kind of reflection.

In CGI its split into two, reflection and specularity, just so you can control the highlight. The high light is the reflection of light sources.

 

for some reason i found ur answer just now,tahnk u very much Tom,brings some "light" into that issue:)