[Mihai]

I've found that's not entirely true Voidmonster. I still use it for walls, with a second bsdf for subtle reflections.

[Voidmonster]

At least based on the test I just completed, it would be about 1/5th faster to use high roughness rather than Lambert.

[Mihai]

Yes, that's a good thing about it A bad thing is I get too dark corners if I use 99 roughness, opposed to lambert. You can see it in your pic as well.

[Boris Ulzibat]

Yes, that's a good thing about it A bad thing is I get too dark corners if I use 99 roughness, opposed to lambert. You can see it in your pic as well.

Is it normal that i get about 3x speed increase using 99 roughness instead of lambert in all objects in the interior scene?
I tried to render 4000*3000 it gave me 28.9 benchmark on 2 sl
while in 640*480 with lambert it gave me not more than 15.
Now i'm doing a preview render of the interior in 1280*1024 - bemchmark says 50 on sl 4.5...
I'm feeling lost, the scene i posted in the gallery section contained some lambert materials and was rendering 3600*2700 at 20 benchmark...
It's a pity i didn't knew that before

[Mihai]

It depends a lot on how bright your lambert materials are. From 220 and up the noise can increase a lot, especially if everything in your scene is assigned this same material.

[Voidmonster]

Examining the results I got even further, I also notice another paradoxic effect.

While the Lambert material took longer to reach SL18, the roughness 99 material shows slightly more noise at that SL.

I take back what I said about Lambert. Now I'm just looking at it with my head cocked to one side like a dog that heard it's name called from far away.

[mverta]

About Lambert:

It's actually faster, cleaner, assuming that you're not using overly-bright values. However, I have often said that you should not use Lambert mode as it is distinctly unphysical looking. What I should have clarified is that you shouldn't use a SINGLE LAYER Lambertian as a material, unless you want rubber, for which it seems perfect. Even then a second layer is great.

A dual layer material, with one layer lambertian, and a "sheen" layer of varying intensity is great for any non-metal surface, like cloth, plastic, wood, etc. The choice between using Additive and Normal blending modes for those materials is personal preference, but many times, additive provides a better blend.

The problem with a lot of archviz renderings I see here is that they use single layer Lambertian materials, and the whole image looks irreperably fake as a result. Personally, my concrete and bricks are dual layer, with one lambertian (color) and a sheen layer, weightmapped. The fall-off nature of the sheen layer reintroduces shading characteristics that Lambertian mode doesn't have.

As soon as you uncheck Lambertian, you're in "metal" mode. If you made two identical materials - dual layers with a sheen - but substituted one Lambertian layer for a roughness 99 layer, you'd see immediately the difference between Plastic and Metal.

For my carpaint, I use roughness 99 base (or lower) with a 2nd BSDF for sheen, because the paint itself is metallic. This is how I did R2-D2's body and dome paint, for example, because they're both metallic-based auto body paint. But for knobs and switches, which are plastic, I use a base Lambertian with low-roughness sheen. Cloth I use dual layer, as well, Lambertian with a high roughness sheen layer on top. Only pure metals, or purely metallic-based materials, or glass/transparents do I use Roughness control for.

_Mike

[The Pixel Artist]

Nice post Mike, thanks for the good incite (as always). I’ve been started to figure this out myself lately since I’ve gotten back into M~R a bit.

[andretto]

thanks Mike,
straight explaination as always


Andrea

[hyltom]

About Lambert: It's actually faster

If I remember well, this seems not true with V1. I already mentioned that long time ago to Mihai.
http://www.maxwellrender.com/forum/view ... highlight= (6th post)

[mverta]

To be honest, it's been awhile since I used 1.0, so that's possible, but doubtful. If 1.0 single-layer lambert materials with reasonable values render more slowly than single-layer roughness 99 materials, well... that won't always be the case.

_Mike

[hyltom]

To be honest, it's been awhile since I used 1.0

Don't say this to me, you make me jealous

[superbad]

To be honest, it's been awhile since I used 1.0

Does that mean you've gone back to beta? Great explanation on the lambertian layered materials, that's a big help, and you've given me some things to try.

[mverta]

Here's an entirely concrete scene (?!)... Just wanted to illustrate the profound difference that Lambertian vs. Roughness 99 can have on a 2-Layer BSDF material in a scene. Whichever one you like, there's no question they're completely different.

_Mike

[mverta]

I use a 90-degree reflectance-only high-roughness sheen with bump and a weightmap. I don't want my concrete to have any straight-on reflection, only at grazing angles.

_Mike