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

[lukx]

Vray manual states that sub-pixel mapping shoudl be off to get more realistic results... but when I have it off I got white noise problems and pixelated edges on bright objects (especially white reflections). How do you guys deal with it ?
I read on Peter Guthrie blog that he's using sub-pixel off ... but I never see those problems on his renders.

[PIXELBOX_SRO]

whats more...try to render with alpha and subpixel on....yuck
its a puzzle for me too

[rivoli]

who knows.. but I guess there's probably nothing fancy about it. just colour mapping, limit materials/reflections brightness, and render to a high enough resolution so that even aliased edges look ok once printed or down sized on a monitor..

[lukx]

whats more...try to render with alpha and subpixel on....yuck
its a puzzle for me too

yeah, alpha is horrible !

[PIXELBOX_SRO]

tried to render 10k image beacause of that...it wont sort the issue of the alpha.
wonder why this is...

[PIXELBOX_SRO]

BTW....PG doesnt seem to render anything that comes with alpha...he renders images together with background which is mostly a backplate from one of his EXRs/HDRIs

[rivoli]

tried to render 10k image beacause of that...it wont sort the issue of the alpha.
wonder why this is...

I never check subpixel mapping, what's the problem with that and alpha channels?

[PIXELBOX_SRO]

the alpha channel comes unfiltered and without any antialiasing......basically pixelated

so then you get a situation where you have the contrast between the building and the sky backplate you put in in post, youll see really ugly pixelation on the edges.
will post an example when i have a second

[vlado]

Can you get me an example for the alpha issue? I'm not sure it should be happening...

Otherwise, having the sub-pixel mapping on might produce different brightness of some effects like glossy reflections, especially if you use the universal settings or some variant. Some people use sub-pixel mapping, but clamp the colors not at 1.0, but at some higher value like 5 or 6.

Best regards,
Vlado

[prima]

So, are you saying that you must render images bigger than a certain size, to use subpixel mapping? And maybe then re-render the alpha channel without it?
It's a bit confusing... by eye, I must say that generally images are better with subpixel mapping checked, even if the log says the opposite.

[vlado]

It's a bit confusing... by eye, I must say that generally images are better with subpixel mapping checked, even if the log says the opposite.

It says that they may be incorrect, not that they will be worse The two things are not the same.

Best regards,
Vlado

[cecofuli]

And don't forget. In some situation (interior + o lot of GI with a few light source, a lot of dark area with glossy wall) the rendering time with sub off is 3x see my old post!

[3LP]

there is indeed a big difference in time, but, there is also a big difference in lighting...

does this mean that (even when we are working in LWF), with the sup-pixel off, we would have more "natural light" ?
that's a great tip, because I have got a lot of situation where LWF doesn't give me enough light and I have to cheat a bit.

What do you reckon for final output? Or, in another way, what do you use?

Thanks

Stan

[cecofuli]

This is the final rendering LINK
I don't remember, but in this situation i use Sub=OFF. For example, right now, in an interior room with a lot of artificial light (IES) I use sub=ON with CLAMP=OFF. Less rendering time and the difference is not so visible (for the client ehehe... ) And less artifact in the super-bright area (crome, metal and light sources). And yes, with sub=ON the rendering is in general a lot better, but = more rendering time and more artifacts. So, in production I prefer turn it ON.

[prima]

So what is the procedure to use subpixel mapping without artifacts? Thanks to all replies, so far.