highlight specu

[lightingparty]

Hi,
i'm trying exterior render because i see a lot of interior renders with corona (which are fantastic).
i have a little problem with highlight specular reflection:
http://www.lightingparty.com/eric/highlight.jpg
the only way is to wait a long time in rendering to have a good antialiasing in highlight.
corona is very fast and It's sad to wait to wait along time only for good aliasing in highlight
is there an other way ?
thanks for this render engine which is for me the perfect one! i would like to finish this picture the next week and maybe it could be possible to have a daily buid to make some other test and also to finally suppress vray !
best regards
eric

[Ondra]

looks like problem with color mapping, try increasing the highlight burn in postprocessing rollout

[lightingparty]

when increase highlight compression i also loose global contrast and this is not what i want. for exemple if i put  a value of 5, i loose too much color and contrast in the sky ... there's some tips in vray to avoid this kind of highlight but of course it's not perfect too...

[Ludvik Koutny]

You can lower PT samples to focus more sampling into AA.

[lightingparty]

thanks for your answers.
i tried that and it's a little bit better, but i made other tests and the only way i found was to use hdri in old style : 1 map in environment, 1 sun (reflection off), and one map in reflection environment (with clamping).
this is exactly the same problem in vray in highlight reflection. In vray there are two option (one is to use subpixel mapping + clamp) or a new option in vray 3.
i think it's could be nice to have something similar in corona because it's terrible to wait render just for specular problem.
I don't want to criticize corona because i know that's what you want is to have the more realistic image. But  i'm not sure we would have these kind of highlights in real world. of course If we made a photo of this scene, we would have lens and glow effect in highlight, buti i think highlights are a little bit to high generally in corona even if reflection are not very high in materials.
i did the same test with vray and the options i mentioned.(exactly the same problem than corona but with the little help of subpixel and clamp it becomes more cleaner and faster.
http://www.lightingparty.com/eric/highlight2.jpg)

[astudio]

I think your HDR file just "overtweeked". Did you get same issue with other hdr files?

[lightingparty]

thanks astudio.
i have this problem with all hdri files.
i made a lot of tests whith different kinds of lighting (i mean , 1 test with only hdri, 1 test with 1 hdri + sun, and finally hdri clamp to 3 ).
and when i made test with corona sun it was the worst .

[astudio]

My feeling, that you (or somebody other) tweaked your hdri in photoshop. There is a lot of direct light vs GI here. May be it's a reason. Try free hdri from viz-people with multiplier 3-5. They give a lot of contrast. You'll no need color correction at all. In my example there is pure hdri.

[lightingparty]

thanks for all replies astudio.
maybe the hdr is tweaked but all my peter gutherie map and  all cg skies do the same!
and when i tested simply rendering with corona sun and sky i have the same problem....:(
each time i have a small rounded corner on polygon i've got the same result...

[astudio]

I'd change HDRI anyway, cause now it looks flat with lack of GI as for me.
1. You may rotate your hdri map left and your specs will go out, you'll receive longer shadows and more GI areas.
2. If you want to store your shadows, you may use rotated hdri only for reflections. This will not 100% physically correct, but will solve the problem.
3. You may use darker color in reflection slot.
4. You may use anisotropy to reduce spreading light in horisontal direction.

[AnubisMe]

try changing the gamma of your HDRI to 0.8

[astudio]

try changing the gamma of your HDRI to 0.8

No. It will give more contrast for sure but with more artifacts.

[Sam75]

Have you tried to reduce "max sample intensity" ?

[lightingparty]

thanks much to every one
Astudio, sorry i don't want this kind of solution . i m thinking "animation" and rotate hdri isn't a good way for me (but sincerely i appreciate to much you're help)
i 'm looking at your image and i m sure you would have the same problem if you add some rounded edges on some polygons which take the sun light. you havn't got any problems because of there is no rounded edges on corner surface.
i'm sure it's like in vray: highlight bright on corner when camera isn't near the object always makes white dots .solutions are to over sample AA, or option to clamp.
Sam75 i tried "max intensity" and it didn't change anything.
It's a common problem of rendering engines when highlights Exceed 1 value. I didn't made test whith the new option in vray 3 for that, but there are the subpixel and clamp option which are not perfect but allow to make good AA in highlight corner without over sampling. It's a pity because I think this kind of problem costs to many rendering time ...but i'm sure corona would be better in the futur.

Astudio , you ve got to try to add some rounded edges on geometries and put a camera as far as possible from objects and make the same test whith hdri or just corona sun/sky. You will have the same problem.