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Help ! Funny banding in shadows and darkspots !


Liquid_Moments
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Hi all

 

Ok so my problem is. When I render a scene with dark areas or a flat dark colour I get this kind of bad gradient effect without enough gradient lines to make it smooth. I have attached an image have a look at the dark wall it starts where the light hits. I have used IR+LC with high settings and vray lights with a sample rate of 30. I am useing vray 1.5 sp2. PC is quadcore2 9550 2gig of ddr3 ram and a nvidia 260.

 

Please if anyone has any ideas please let me no. If you need a better image demonstrating this let me no. Thanks !

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It's an artefact known as "banding" which occurs when there is insufficient bit-depth to represent tonal gradation, that is, there's not enough data in an 8-bit image to render smooth tonal gradients.

 

Best workaround - render your images at 16-bit or higher, keep this depth throughout the entire workflow and only convert to 8-bit when you've finished.

 

Here's a bit of reading to let you know what's going on...

 

http://articles.j-roumagnac.net/english/digital-photography-postprocessing/basics-opening-the-raw-file-in-photoshop-why-16-bits/

 

 

Oh, and welcome to both CGArchitect and the world of "dynamic range, linear-workflow and more info about digital colour than you ever wanted to know" ;)

 

Plenty of great info on the following thread too...

 

http://www.cgarchitect.com/vb/35112-color-modes-will-drive-me-crazy-some-day.html

Edited by shaneis
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Thanks for the reply shanies.

 

How would I go about setting up max or Vray to render at 16bit ? I have my desktop settings running at 32bit I thought the program would run at that bit rate ? It's not just the rendered output file it shows up in. It's also the render before I save it as a tiff jpeg etc !

Edited by Liquid_Moments
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Thanks BrianKitts for taking the time to reply. But I already have that setup ! Ok I have attached a zip file with the test scene in it, if anyone could hit the render button and take a close look at the dark wall to see if the same thing is happening. It is subtle but it's there. That would be great thanks gal's and guy's.

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Thanks for the reply shanies.

 

How would I go about setting up max or Vray to render at 16bit ? I have my desktop settings running at 32bit I thought the program would run at that bit rate ? It's not just the rendered output file it shows up in. It's also the render before I save it as a tiff jpeg etc !

 

Don't get display settings confused with the image file's depth. When you render, you're simply creating a file. Your monitor's/ OS's display settings simply determine how that file shows up on-screen. As Brian pointed out, just make sure your display is set to 32-bit. Calibrate your monitor as best you can. Here's a basic one to get you going http://www.3drender.com/light/calibration.htm

 

As for rendering to 16-bit in Max, sorry, can't help you there - I don't use Max. Somewhere amongst the global render settings, you'll be able to choose "RGB" or "RGBA" and also 8-bit, 16-bit or 32-bit... You'll need to choose a file format that supports 16-bit colour, best would be a 16-bit TIFF.

 

One other thing when I enlarge one of the materials in max's material editor the banding shows up on that to. Hmm I may have to look into my video card. any suggestions would be great.

 

You may need to fiddle with the way your video card displays Max's viewport. Direct3D or OpenGL. Search these forums for info on the preferred setup. Maybe look into the Maxtreme driver? (spelling could be wrong).

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Thanks for the big reply shaneis great stuff. I have spent abit of time researching and playing with my video card setting's, max and vray's different settings, still nothing has changed. Seems you cannot setup a 16bit or 32bit render in max or vray but you can with mental ray ! also I have found that max seems to think my renders are in 64bit RGBA is this possible with the 32bit version of Max ? I wonder. Also I have found if the scene is like a daytime lighting solution you don't get banding. I have been useing max since version 2.0 and I have been able to fix any problems I have come across but this has me stumped !!! I will continue to research I think !

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