Overbright antialiasing

[Garryclarke]

Hi,

I'm a bit of a newbie with VRay so appologies for posting what may be a simple question.

I'm having a problem with overbright colours not antialiasing the way I want them to.



The antialiasing around the light and it's reflection are very rough looking. I understand why this is happening (a very bright pixel antialiased against black is still very bright), is there any way to get a nice smooth edge on these bright objects.

- Garry

[joconnell]

You can use one trick to make renders quicker if you're sending out render into a linear comp package, are you doing any layer based compositing afterwards? If so, nuke / fusion / afx or are you going straight from the render and treating the beauty afterwards?

You have three choices, Raise your max aa samples (probably a bit slow overall), Turn up your light samples (have a look at the shadow behind the teapot to see is your shadow clean, if it is then your shadow samples are possibly okay) or lastly and probably more precisely, raise your reflection samples on the material of the teapot. Don't be afraid to go up to big numbers on it as it's only setting a theoretical limit for vray to use, not an absolute number that it will use.

[Garryclarke]

Hi,

Nope, none of that is working. I don't know if I have anything else set up wrong, I've attached the file if you want a look.

I'm using a linear workflow but saving my images as 8bit per channel. So that the saved images are good to go. I'm not doing any fancy compositing.

I'm getting a lot of this in reflections of HDRI skies on an ocean surface, so far I've managed to keep the client happy by not pointing the camera into the bright refelections but I would like to get this problem solved.

https://dl.dropbox.com/u/32876363/overbright_test.zip

[zeronove]

I quote everything joconnell already suggested and...
...maybe you can make the sampler work easier just using a softbox texture as lightplane ...as you noticed the problem is ultrabright pixel against black background ...so just put a gradient in the middle, it should be even more realistic

[samuel_bubat]

Hi,
turn on "sub-pixel mapping" and "clamp output" from the environment dialogue.

[Garryclarke]

Hi,
turn on "sub-pixel mapping" and "clamp output" from the environment dialogue.

Brilliant!

That's exactly it. I'd tried Sub-pixel mapping and clamp output but not both together.

Many Thanks

[joconnell]

Gary - could you pop this out as a max 2012 file?

Last thing I'd suggest is if you're using the files as 8 bit you can go to the colour mapping tab and use the sub pixel mapping set to on, and then also turn on clamp and set your value to somewhere above 1. What Clamp will do is kill the pixels bright values at whatever value you choose (1 being normal white - go by the values of your light multiplier as a guide). If your light is up around 30 or something quite bright then turning on a clamp of 1 will chop the spec / reflection values down to 1 before they get sampled / anti aliased. It'll make like easier on the sampler but it'll kill the dynamic range of your image - you still want to get some clipping for it to look realistic, so maybe experiment with values between 2 and 5 to see what gives you a good combination od speed but also the correct look.

Of course if you were doing a heavy float based compositing workflow you'd want to keep some of those really bright values for nice streaky motion blurred highlights or those cool puffy out of focus circles, but if you're going right for the render then this might be a better compromise.

[Garryclarke]

Hi

Here's the file in 2012 format.
https://dl.dropbox.com/u/32876363/ov..._test_2012.zip

Thanks everyone for the help, there's a lot in VRay that's new/different than what I've been used to.

Cheers
Garry