what is the trick to render corrctly with sub-pixel mapping off?

[PIXELBOX_SRO]

tried to replicate the problem but i am not succesfull....perhaps it has been fixed??? dunno...will try to find the older scene

LUKX: can you show the alpha issue on a sample?

Ta

[cecofuli]

If you turn ON the sub, some artifacts disappear near a bright edge and near some crome shaders.
But the light is a lot, a lot different, especially with LWF with universal setting (QMC + LC , AA 1 / 100 blah blah)
and rendering time is, with Universal setting 3x. So, what do you prefer?

SOLUTION A (LWF + Universal setting + SUB OFF)

. Quality due to the Universal setting and BF
. Fast setting (Only noise threshold)
. Possibility of artifact (Sub is OFF)
. High rendering time (x3 or x6 times)
. great light distribution


SOLUTION B (LWF + Universal setting + SUB ON)

. Quality due to the Universal setting and BF
. fast setting (Only noise threshold)
. no artifact (Sub is ON)
. low rendering time
. worse light distribution

SOLUTION C (LWF + classic IM/LC + SUB OFF)

. Less quality (we don't use BF)
. slow setting (we need to play with subdivision for shader, lights etc...)
. Possibility of artifact (Sub is OFF)
. fast rendering time
. great light distribution (with sub ON or OFF, in this case, the light distribution is very similar)

SOLUTION D (LWF + classic IM/LC + SUB ON)

. Less quality (we don't use BF)
. slow setting (we need to play with subdivision for shader, lights etc...)
. No artifact (Sub is ON)
. fast rendering time
. great light distribution (with sub ON or OFF, in this case, the light distribution is very similar)


Original rendering resolution is 320x200. Resize in PS to 800x500 for better view.



PS: in the older versions of VRay, subpixel was not exposed and was enabled by default

[prima]

Cecofuli, that is some good insight. But, do we have to deal always with a "possibility" of being artefacted, or there's a certain, assured way to avoid it?
I could use subpixel off, if the result is better, say for a production, but I must be sure of the result.
I mean, what origin have those problems?
I'm speaking with in mind LWF, IM+LC and clamp on.

[PIXELBOX_SRO]

i use C or D

PLUS

i sometimes check sample visibility for IM and go for 1 for retrace threshold in LC
i check the "dont affect colors" in color mappind and use 2.2 gamma and SRGB button ON in the VFB

this gives me result almost like universal method and is way faster

[cecofuli]

In my experience, as you can see in the screen, for interior LWF + IM/LC + Sub ON and Clamp on at 4-5 is ok for avoid artifacts and sure of the result.

But, in some situation, like my exterior, I use LWF + USetting (QMC+QMC or QMC+LC + SUB ON) due to the high detail, a lot of geometry, trees and grass.
Yes, on the trees, the glossy is better with SUB OFF, but rendering time will be too high for my taste... And the difference is only in the highlight in the trees foliage and grass...

Oh, yes... retrace threshold and Detail enhancement could help the final quality (not the rendering time!)