jagged lines where lights are used

[stayinwonderland]

I remember I had this problem in Vray 2.x and there was some kind of retract threshold (that might be a guess) which solve this problem.

 

It's basically if you have a really bright light next to a contrasting dark area and it comes out really jagged and aliased.

 

Since using Vray 3.x I can't seem to figure out which setting to use to get rid of that.

[Corey Beaulieu]

Can you post an example?

 

I've never had this issue. What are you saving as? I have seen banding here and there, but usually with 16-bit tiffs or EXR it isn't an issue.

[stayinwonderland]

 

Here you go, excuse small size (under NDA).

 

It's mainly where I have a vray light material.

[Nicolai Bongard]

This is a problem with the antialiasing having trouble since there is a high difference in intensity (The light is really bright next to a surface that is darker) and thus it has a problem smoothing out the difference of the pixels. From a quick google, the clamp output in the color settings seems to be the recommended fix.

 

You could also try enabling :

 

Max ray intensity – Suppresses the contribution of very bright rays, which may typically cause excessive noise (fireflies) in the rendered image. Its effect is similar to the Subpixel mapping + Clamp output options of the Color mapping section, but the Max ray intensity is applied to all secondary (GI/reflection/refraction) rays, as opposed to the final image samples. This allows fireflies to be effectively suppressed but without losing too much HDR information in the final image. Similar to the Subpixel mapping option, the Max ray intensity introduces bias in the rendered image, as it may turn out to be darker than the actual correct result.

[stayinwonderland]

Thanks. I turned on clamp output but it didn't really change anything until I set it to 1.5 which helped with certain lines reasonably well.

 

Max ray intensity was already on by default and set to 20. Not sure what value would be appropriate there though.

[Francisco Penaloza]

This is the thing when you use visible lights or self-illuminated object. If you take the same situation in real life a photo/video camera will display a soft/blurry transition between both areas, this is part of the glow we see.

 

In your case, if you turn on Bloom and Glare effect in VRay Framebuffer that will help you to recreate better that situation.

 

Having said that, the problem is antialiasing, so the first solution could be rendered larger, so you have more pixels working in those areas, sub-pixel mapping and clamping will also help. reducing the amount of light information in the bright areas.

 

Max Ray intensity was created to resolve this issue and also firefly from brute force method. You need to decrease the default value to something under the Max brightness of your material/light.

 

As a rule of thumb I never set my self-illuminated material to a very high value, just bright enough to differentiate and the use a self-illuminate pass to enhance in post-production, also glare a bloom is recommended.

 

Vlado also recommends using progressive rendering instead of bucket in these situations to have a better antialiasing solution.

[Chris MacDonald]

As Francisco said the issue is with the antialiasing filter and using floating point values (which clamping removes).

 

If you have (for example) a window frame that returns a value of 0.5 and the outside/light returns a value of 5 then the antialiasing sampler will subdivide between these two points of high contrast and try to find a more reasonable (less contrast) value. If no such value can be found then it will return an average between the two pixel values so 0.5 + 5 / 2 = 2.75 - still brighter than 1 (255,255,255 in 8 bit RGB).

 

Obviously if you clamp these values then the average pixel values become something that the antialising filter can deal with, but this is at the cost of losing the dynamic range of the image which is useful in post. I find rendering at higher resolutions (thus downscaling the effect) and using bloom/glare to be preferential to clamping the output, and using a soft antialiasing filter too (the VRaylancosz with a value of 2.5 to 3 produced soft results). Sharpening filters always exacerbate the problem and even cause ringing artefacts.