weird colors in overburnt areas...

[gustavljunggren]

So recently i´ve been having issues with weird pink, blue and green colors turning up in overburnt areas of an interior render. clamping output fixes it but i really want to render this scene unclamped for post-prod. purposes. im using linear multiply. I can render the scene underexposed (gets rid of artifacts) and correct exposure in post but i really want to try and render it out properly. Im sure this has been up before but cant seem to find anything about it so hopefully someone can help me out.

[gustavljunggren]

BTW this was my first post so hello everyone

[Francisco Penaloza]

if you could post some screenshot of your scene and settings, it will really help to debug your problem.

What type of lighting are you using? HDRI or Sun/Sky?

are all your materials V Ray?

do not use extreme values in your colors such true white 255 or true black 0. same apply to other colors and textures.

If everything is correct and you still have strange clamped colors, needless to say there is nothing wrong to use some color mapping during rendering. You can setup reinhard instead of linear and reduce a little the burn value, be sure to select affect color mapping only, this will still give you a very wide depth image to post process later.

 

Be sure that in your V Ray buffer the button Force color clamping is always on.

[gustavljunggren]

Thanks for your reply Francisco. Im using a single HDRI for lighting. (Peter Guthries 1044 sky) My settings are nothing special. just for draft passes. i use adaptive DMC 1/16 with sample thresh at 0,02. linear color mapping with "dont affect colors" ticked. Brute force + LC GI. 20 brute force subdivs and 800 LC samples. All Vray mtrls with no extreme whites or blacks (White mtrls around 235.). Going with Reinhard and a low burn value fixes the problem as well but i really would like to try to keep it as linear as possible. But maybe youre right in going with reinhard and losing a little bit of depth wich i guess really wont matter that much in post anyway, it´s more about me being stubborn wanting to render unclamped and completely linear. i will try to post i pic of the weird areas later today

[Francisco Penaloza]

The thing is you should not get crazy color blotches, even if your image is over exposed you should just get over bright areas, burn bright. maybe some color spill but not weird colors circles and such. Then you can tone mapping outside of Vray and get a nice image.

Maybe you are "crunching" too much your HDRI?? I know lots of people lower the inverse gamma on the Gutrie HDRI to get sharp shadows. that can produce artifacts if it is too exaggerated.

again it is hard to pin point your problem without an image

[gustavljunggren]

Yup thats pretty much how i see it aswell. White overburns are fine since im planning to correct them in post and i need really bright overburns (especially in metal reflections) for bloom and glare. The gamma of the hdri is set at around .84 in this case so i dont think thats the issue. I´m in the middle of uppgrading hardware and therefor i havent been able to post i screenshot but i will as soon as i can. Found a thread from a while back (http://forums.cgarchitect.com/69941-odd-colors-vray-frame-buffer.html) where someone had the same issue and in that case it seemed to have been a texture issue??? really not getting that but anyway... pics coming up

[gustavljunggren]

I´m in the middle of upgrading hardware and therefor i havent been able to upload an image yet but will do asap. Regarding the HDRI settings i keep the gamma around .88 for this one so i don´t think thats the issue but i found this post http://forums.cgarchitect.com/69941-odd-colors-vray-frame-buffer.html from a while back where someone seemed to have the exact same issue and apparantly its a texture issue, however i dont understand how or why. The mtrls where the "blotches" keeps coming up does have a lot of texture-maps loaded but the amount of maps in a mtrl shouldnt really be restricted other than by RAM right?

[gustavljunggren]

hmm so while rendering out a test to post i realised that the saved image looked allright.

 

But in the vray VFB it looks messed up:

 

Must be some setting in the vfb i messed up

[Francisco Penaloza]

Gustav, click the button "Force color clamping" This has to be enable all the time, this does not affect your image, just let you see your render in Color within the depth of your monitor.

in your frame buffer bottom left, second button.

[gustavljunggren]

Thank you francisco but that leaves everything solid grey with white pixels in "the weird" areas. (Feeling realy stupid right now)

[Francisco Penaloza]

There may be something else that you already changed to compensate your early problem.

Do yourself a favor and reset all values of V Ray, go to render engine in Max and from the drop menu, select Scanline, then when it change the interface, change it again to V Ray, now everything should be default.

Just turn on GI and do a test render, it should work now.

on V Ray 3 by default it should render with no problems.

[gustavljunggren]

aaaaaaaand i figured it out... click and hold the force clamping button. somehow i must have chosen the questionmark force clamping tool by accident but now everything is working fine.... thank you again Francisco

[Francisco Penaloza]

No problem, glade to help

[Corey Beaulieu]

Just so you are clear, the "weird colors" showed up because you are overexposed in that area. They code the RGB channels and indicate which channels are above 1.0. When they all are, the color goes black.

 

You can, and maybe should, work with Force Clamping off most of the time and then fix these issues in your camera settings.

 

Just my opinion.