Clamp output option at frame buffer

[Micha]

Hi,

often I use the unclamped output and the frame buffer curve control to simulate an analog film gradient curve to catch the brightest parts of an image. Something like a manual adjusted burn value at frame buffer level. Works fine and I use it daily, but ... I miss the antialiasing of the "clamp output" option. Could it be possible, that this calculation is placed at the framebuffer too. If I can save a 8 bit png from the curve corrected frame buffer image, why not with clamped output?

Thanks,
Micha

PS: I use Vray for Rhino, maybe there is a difference.

[sv]

isn't the anti-ailising calculated during the render depending on a lot of factors and values?
I don't think it could be just 'added' as a post thing as you suggest.

'Poor' anti-ailising of high dynamic range pixels in an image is only evident because there is so much variation between adjacent pixel values - you have alising because the AA filter or image sampler is trying to ailise between values way greater than 1 still, or often the 'inbetween' values which would produce anti-ailising are still greater than 1.0 float, so it's displayed as a pure white pixel which leads to ailising.

Are you suggesting doing AA based on clamped values even for un-clamped images? >how would you be able to calculate what those 'inbetween anti-ailised' pixel values were - i think it would lead to incorrect results.

I think the only way would be to just render with clamped output on....

[Micha]

Only I mean to clamp unclamped VFB images. You mean, the clamp calculation makes that more samples a shot? I hope Vlado will tell more.

An additional wish: it coul be good to get the reinhard burn control at the frame buffer too.

[DaForce]

Wouldnt Vray for Rhino requests be more appropraite over at the Vray for rhino forums?

[vlado]

Well, since the V-Ray VFB specifically is the same everywhere, I suppose it doesn't matter where it gets posted... I will see it here more likely than on the Rhino forum

Best regards,
Vlado

[Micha]

Thats my experience too, if Vlado and general Vray request than Chaosgroup.

... and don't forget please: is it possible, to get a VFB clamp and burn option?

EDIT: Some weeks befor I post at the VfR forum, that the snap-to-grid of the frame buffer curve dosn't work. Is it a VfR problem or Vray general? Is it on the bug list?

[studioDIM]

When you clamp, you reduce the values to 0-1.
Since this is done before rendering, the speed of the AA also changes (do some simple test. you'll see that's what happens), due to a restricted range, and less data to be taken into account.
While it's easy to discard data (going from unclamped to clamped, for instance) it appears fairly impossible to me to go the other way around.
Vray would have to redo the AA pass -at least- on the fly, if those unclamped pixels were somehow stored away, and were brought back.

My 2 cents, Vlado will have a wee bit more to add, i reckon.

Lele