MyLittleSomethingExperimental

[lacilaci]

An early wip. I'm still having a little problem with those white dots appearing in the rendering. This is ca. 3hr+ rendering. I'm using "rawafake" sky and sun with manualy set color to 200,200,200 using any color(even just a little saturation) only with this setup I get low presence of those fireflies. Using latest legacy build...

[lacilaci]

Hi... testing new dec07_2012 legacy build to see how it handles those white spots... and no luck here. Maybe I'm doing something wrong, but it looks that lots of very dense geometry with reflection component is enough to make these fireflies appear.

[lacilaci]

I've simplified the material so it has only a diffuse color and a bit of reflection.. no masks no translucency, refraction... And I tried several different render settings nothing makes it go away. They're less prominent if I use low sky and sun intensity values but still appear here and there plus the longer the render goes the more of them seem to appear. Turning image filtering off makes them smaller turning it on with default values(cone 1,5 + internal res 2) makes less of them appear but they're bigger :D....

So either I'm doing something very wrong. Or there is a problem with reflection and lots of dense geometry...

Btw can't run assert version of corona(max will crash, not able to load plugins)

[Ondra]

ok, post the scene - http://corona-renderer.com/upload/

[lacilaci]

Ok, uploading now... Let me know if somethings missing. There is a max file and 2 proxies which goes into the Cscatterer and a ground texture... it's 2013(64bit)

[Ondra]

ok, mystery solved: you have perfect mirror reflections on the grass leaves. This combined with the geometric complexity of scattered grass causes random speckles to appear where the grass blade aligns to reflect the sunlight. You need to blur or remove the reflection on the leaves.

[Chakib]

Did you use Progressive mode or VCM here ?

Keymaster : so the reflection with scattered objects and opacity are the problem ? will remove its reflection  in my scene and see

[lacilaci]

Well... It does happen even at glossy values around 0,5 for refl. I have to blur the reflection so much that it really doesn't matter if I use any...
So, there is no way to make corona sample away this kind of artifact?

[Ondra]

Well... It does happen even at glossy values around 0,5 for refl. I have to blur the reflection so much that it really doesn't matter if I use any...
So, there is no way to make corona sample away this kind of artifact?

It is not an artifact. What you are doing is scattering tiny mirrors on the ground - it makes sense you'll see random bright flashes all over the ground where it aligns to reflect the sun. So you need to either dull the reflection, or make the sun not be visible in it (probably impossible with current set of fakes, but will be in the future)

[lacilaci]

I get it I get it!! Don't yell at me :D:D:D lol... I was just thinking that reflection would be much less visible using very low values for sun (color and intensity) and yes, hiding sun worked only for direct visibility but is seen in reflection. Thanks for help with this :) I'll make some adjustments for the materials then...

[Ludvik Koutny]

This is a bug, just not in raytracing, but in the way samples are averaged and filtered. Other renderers filter them correctly, but unfortunatelly corona just splats the superbright value onto surrounding pixels creating large white dot with very sharp border.

[lacilaci]

That makes sense since there was larger amount of smaller bright spots without image filtering and less amount but bigger spots with 1,5px cone filter. However I partially solved the issue with very low glossiness values as well as reflections so it's ok but in some cases it might be pretty tricky to correctly tonemap lightsources visible directly or in reflections to get rid of aliasing.

I'm thinking, how would you solve a situation like: night street view after rain with lots of light emiters and tons of wet reflective geometry in the background? I need to try this :D

[Ondra]

DOF the shit outta it and apply some artsy bokeh :D

[Ludvik Koutny]

I hope it will be solved soon. I consider it a bug... Other renderers handle it correctly so that you don't see such artifacts :)

[lacilaci]

DOF the shit outta it and apply some artsy bokeh :D

What a solution!! :D You should add that at the end of some future manual "...And if anything else fails DOF the shit outta it and apply some artsy bokeh..."

[lacilaci]

I hope it will be solved soon. I consider it a bug... Other renderers handle it correctly so that you don't see such artifacts :)

Definitely... I don't even know, is this an image sampling error in corona, or image filtering? Or does it need some advanced alien technology from this guy?

[Ondra]

I consider it a bug...

I don't, so good luck getting it "fixed" ;). The proper solution would be probably disabling the visibility of sun in reflections.

[Ludvik Koutny]

I consider it a bug...

I don't, so good luck getting it "fixed" ;). The proper solution would be probably disabling the visibility of sun in reflections.

So now you like ugly fakes, huh? As i already shown you on iRay examples, sun is there, but the dot is correctly dim, it doesn't splat white on the surrounding pixels, but properly averages the value. It's about what is pleasant to the eye. If you don't consider it a bug, or intend to fix it by completely disabling sun reflection, then good luck selling your renderer.

[lacilaci]

Ok, seriously now. This might be a big issue in animation of some complex environment. We have not seen a full featured CGI environment with all sorts of artificial lights to enhance the atmosphere during an animation with lots of moving objects etc and all extremely sharp in 1080p. If corona continues doing so well and have all the popular features as hair and sss and so on(Btw I can imagine some furry stuff:D having shader with sharp reflections where it could be pretty problematic to avoid this issue) it will face situations like this.

Cause if some popular studio decides to try corona out doing some crazy shit, then avoiding direct and in reflection visibility of lightsources because of some aliasing or image filtering issue is out of question. You can't change the look of the scene in animation and tell the client it can't be done this way. As a studio you would have to choose another renderer and your product reputation goes down.

And this is something you know of. How much can appear once it goes commercial what you don't know about cause it has not been tested? You won't know how and suddenly there will be tons of people arguing with you why the product they bought is not working as expected. This is not a missing feature you can make your future client aware that it does not have. How would you explain to them that the white overkill:D is normal and how would you make customer aware of this. Would you state this behavior in features category?

Like it or not, once you get this commercial you will be sooner or later forced by some client to make this go away cause money plays. Why not do it before it is commercial to save time for future not known issues you will face? I don't know who do you want to aim your product at. As an individual you can live with this, not a really big problem. But as a studio with lots of bought licenses and some paid courses(big studios will gladly pay you to come there and teach their people how to use corona more effectively etc) you would be much less tolerant to stuff like this.

I wish you the best, don't think of this as a complaint, I love corona it has massive potential. I don't care, I haven't paid for corona now and I don't care how you do your stuff. But try statement "good luck fixing it" to someone who buys your product :D good luck with that man:D

[Chakib]

Ok, seriously now. This might be a big issue in animation of some complex environment. We have not seen a full featured CGI environment with all sorts of artificial lights to enhance the atmosphere during an animation with lots of moving objects etc and all extremely sharp in 1080p. If corona continues doing so well and have all the popular features as hair and sss and so on(Btw I can imagine some furry stuff:D having shader with sharp reflections where it could be pretty problematic to avoid this issue) it will face situations like this.

Cause if some popular studio decides to try corona out doing some crazy shit, then avoiding direct and in reflection visibility of lightsources because of some aliasing or image filtering issue is out of question. You can't change the look of the scene in animation and tell the client it can't be done this way. As a studio you would have to choose another renderer and your product reputation goes down.

And this is something you know of. How much can appear once it goes commercial what you don't know about cause it has not been tested? You won't know how and suddenly there will be tons of people arguing with you why the product they bought is not working as expected. This is not a missing feature you can make your future client aware that it does not have. How would you explain to them that the white overkill:D is normal and how would you make customer aware of this. Would you state this behavior in features category?

Like it or not, once you get this commercial you will be sooner or later forced by some client to make this go away cause money plays. Why not do it before it is commercial to save time for future not known issues you will face? I don't know who do you want to aim your product at. As an individual you can live with this, not a really big problem. But as a studio with lots of bought licenses and some paid courses(big studios will gladly pay you to come there and teach their people how to use corona more effectively etc) you would be much less tolerant to stuff like this.

I wish you the best, don't think of this as a complaint, I love corona it has massive potential. I don't care, I haven't paid for corona now and I don't care how you do your stuff. But try statement "good luck fixing it" to someone who buys your product :D good luck with that man:D

I agree with Lacilaci, hope the major issues will be fixed soon.

I'm planning to buy the final release of Corona or the beta stable one if it will be for sell, so guys i'm waiting for your big effort to improve and fix this baby and limit the fakes inside it, Good luck !

[Ondra]

But try statement "good luck fixing it" to someone who buys your product :D good luck with that man:D

That was meant specifically for rawalanche, because he can be quite annoying when something is not done his way ;). Here is more part of the development team than a customer ;).

[maru]

Here's a very quick scene with a 4min render and almost no fireflies. You must be doing something wrong with your materials, environment or render setup. Maybe it's because your grass geometry is so dense and there are some reflection artefacts where two blades interpenetrate.

[lacilaci]

Here's a very quick scene with a 4min render and almost no fireflies. You must be doing something wrong with your materials, environment or render setup. Maybe it's because your grass geometry is so dense and there are some reflection artefacts where two blades interpenetrate.

I already fixed that issue changing the materials... And unless those white spots on your trees and on the ground are some flowers, then you might have this problem aswell :)

[maru]

No, they are reflections, but when I zoom I can see they are soft. Your renders have very strong, one pixel sized fireflies.

[Chakib]

Here's a very quick scene with a 4min render and almost no fireflies. You must be doing something wrong with your materials, environment or render setup. Maybe it's because your grass geometry is so dense and there are some reflection artefacts where two blades interpenetrate.

Dense or not, it should be good for any kind of clean geometry man !

Try your scene at night lighting and put some glass and emitters, and show us the result

[lacilaci]

Well that was in fact reflection aswell... The problem was more apparent because I used high glossiness values and I got rid of it by tuning down reflections a lot. Here it's not a big deal cause you wouldn't expect to see in scene like this some objects reflected on the grass blades or so.. But you might come across a situation where you would need to see some clear reflections from lots of objects and there if you had a refleced lightsource it may be tricky to fix that.

Even in your case let's say that you are ok with those overbright spots etc. But it's a still render. I'm wondering how would those white spots in reflections behave in motion. I'm guessing they would randomly appear and disappear during animation since they're very visible small sharp and seen on very small area only in a specific angle where the refl. sees the sun/light so I doubt that the transition would be smooth with wind blowing animations over trees and grasses and camera in motion. But again. For vegetation where it doesn't matter, tuning down relfection works ok.

[lacilaci]

I wonder if some implementation of physical camera with the ability to tonemap overbright pixels would solve the issue. Or maybe a feature in post processing category to limit somehow framebuffer max intensity.... You know, somehow limit those overbright values intensity. Cause it looks like a regular situation when aliasing appears in overbright parts of scene and you need to tonemap the image to get rid of it.

[Ondra]

You can do that even now, just use VFB internal resolution > 1 AND aggresive tone mapping (high value of white multiplier)

[lacilaci]

I'm actually testing that now :).... I hope this will work.

[lacilaci]

No luck. The sky and overal image goes darker/less contrasty but even with highlight burn at 5000 and internal res at 3 its those overbright pixels are still there when using highly reflective material even though due to the overall darkening they're darker aswell :D. It's like those values are out of range no matter what you do. I'm gonna try some highlight fixing on this in post to see if it's even possible to tone them down.

[Ludvik Koutny]

I have never experienced this kind of issue on a foliage rendering, mostly because i have set up foliage materials in a realistic manner. Non the less, i get unacceptable artifacts when rendering glass objects under direct sunlight. :(

[lacilaci]

I have never experienced this kind of issue on a foliage rendering, mostly because i have set up foliage materials in a realistic manner. Non the less, i get unacceptable artifacts when rendering glass objects under direct sunlight. :(

Sure, I agree that my original setup was too reflective, not very real... I've fixed that but I have that scene right now at disposal so I'm trying stuff on the foliage with high reflectivity, so even if not real, it's good enough example to get that bug happening.

[tomasd]

The one drawback of physically based renderer is that if you throw at it physically incorrect materials, it will blow up in your face.
The real pro solution is to yell at your modelers to get it correct (true story).

Glass under direct sunlight can be really really tricky with many internal reflections.

[maru]

I know nothing about supersampling in Corona, don't know how it works, but in vray you have a setting that would probably fix issues with high contrast between pixels like in grass reflections - it's called "sub-pixel mapping" and basically it averages the colour value between X points BEFORE they get represented as a single pixel in output rendering.

[tomasd]

Corona can do the same, and it definitely helps.

The other problem however is, that, as far as I understand the scene settings, flickering bright spots are actually correct.
If you have a lot of complex geometry (grass) that is highly reflective (mirror-like), then it is pretty much exactly the same as when you look at a road covered in broken glass on a bright day.
We don't have that many bright days now, but the ball season is coming, so maybe a better yet example would be a sequin dress like this:


Lot of tiny reflective surfaces, whenever anything moves it will flicker. And, thinking about the dress, I guess everyone will agree this is what should happen on it. Now if you model grass that (from distance) it looks pretty much like this, it will (and should) behave the same. Bottom line is, physical grass is not highly reflective, so neither should be its material in physically based renderer.
(I know it has been fixed, but I like the explanation with sequin dress, so there)