My Corona Questions.

[Lnt]

Hello,


I've recently decided to give it a try and learn Corona, so for the next months(?) i will concentrate my efforts on learning as much as i can.
I have average experience with 3DS max and Vray ( the software that i am planning to replace ), but i will not give up on Corona until i manage to learn it on a satisfying level.

I made this thread ( hopefully i didn't break any rules ) in order to have a place to ask various questions that i might come across.
I have already read most of the official tutorials and some other threads around here, but there are things that i could not figure out so i might need some help.


Question 1:

This is my first time i render something in Corona, and for some reason my image has a lot of noise.
I already added the direct and indirect passes like in the tutorial, but they both very noisy and i cant figure out why. ( i haven't saved them )
I am using a HRDI for the environment, corona sun, and portal lights on the windows.
So i would like to know, if this noise is because of the lack of light/bounces, or because of the settings, and how can i fix it?

image attached


PS: I did manage to get most of the noise out in a small resolution image, but it took around 9 hours or so ( is that normal?, m i doing something wrong? )


Specs:
Operating System: Windows 7 Ultimate 64-bit
Processor: Intel(R) Xeon(R) CPU E3-1230 v3 @ 3.30GHz (8 CPUs), ~3.3GHz
Memory: 8192MB RAM
Card name: NVIDIA GeForce GTX 650
Display Memory: 4043 MB


Thank you.

[romullus]

So i would like to know, if this noise is because of the lack of light/bounces, or because of the settings, and how can i fix it?

Neither. It most likely that your scene is incorrectly setup, e.g. bad geometry, wrong materials, incorrect use of lights, but it may be hard to pinpoint the source of the problem without seeing the scene.

I made this thread ( hopefully i didn't break any rules ) in order to have a place to ask various questions that i might come across.
I have already read most of the official tutorials and some other threads around here, but there are things that i could not figure out so i might need some help.

It would be better if you'd create new topics for each separate problem/question, instead of writing it all in one. That would make searching for an answers a bit easier task for future visitors.

[maru]

Hi, what are you using to load that HDRI? Is it by any chance Vray loader? Is the scene converted from Vray or made for Corona from scratch?

I am using a HRDI for the environment, corona sun, and portal lights on the windows.

There are no portal lights in Corona :) - so just to make sure - what did you put in there? Here is the official guide: https://coronarenderer.freshdesk.com/support/solutions/articles/5000501660

Also, remember to put portals in all windows - not only the ones which are visible to the camera.

[Lnt]

Neither. It most likely that your scene is incorrectly setup, e.g. bad geometry, wrong materials, incorrect use of lights, but it may be hard to pinpoint the source of the problem without seeing the scene.

It would be better if you'd create new topics for each separate problem/question, instead of writing it all in one. That would make searching for an answers a bit easier task for future visitors.

Well i haven't changed much from the default settings or lights.
I loaded the HDRI in a corona bitmap without changing anything. for the sun i reduced the intensity to something like 0.05 and increased the size to 15
The materials are mostly converted or created by me, with simple corona materials and small changes on the reflection and bump.
I haven't tried to do a render with an override material since i began importing more models in, i will give it a try and see if it works.

I agree on making more topics for different questions, hopefully i wont spam to much.

Hi, what are you using to load that HDRI? Is it by any chance Vray loader? Is the scene converted from Vray or made for Corona from scratch?

There are no portal lights in Corona :) - so just to make sure - what did you put in there? Here is the official guide: https://coronarenderer.freshdesk.com/support/solutions/articles/5000501660

Also, remember to put portals in all windows - not only the ones which are visible to the camera.

I used Corona bitmap to load the HDRI.
The scene is a mix, some models were imported with vray materials, but i tried to look at each of the converted material to see if everything looks right, is there anything special that i should look at once i convert a vray material?

I apology for my bad habits :D, i meant to say portal material on some simple planes. I added them on every window, on the exterior side of the window.

I will add the portal again and see if that helps


Thanks a lot

[maru]

Also please make sure that all window glass is set to thin mode.

[Lnt]

Hello

Im back with a quick question.
Does it matter if i set the render time to 25 hours compare to simply letting the render with no time limit or setting a higher time?

For example: i had a scene and the time limit to 25 hours, and when completed the render was ok. However after that, ive set the time to 40 hours for the same scene, and at the 25 hour mark the render was still very noisy.

Hope that made sense, thanks

[maru]

It does not make sense - this definitely shouldn't be happening. Setting time limit has exactly the same effect as manually clicking "cancel" at given time. Please check if you are not getting any error messages or warnings from Corona. If you are still experiencing this problem, you can submit a new support ticket: https://coronarenderer.freshdesk.com/support/tickets/new

[Lnt]

Hello,

Back with another question about an error i keep getting

I looked at https://coronarenderer.freshdesk.com/support/solutions/articles/5000675886 and did what was there, but there was no change
i also deleted every map for this material and i re added them without any luck.

I would also like to ask if this kind of problems can increase the render time by such a huge amount, since in 12 hours it barely render 6 passes of a noisy image. ( used to render the same scene in 3-4 hours before this problem )

[romullus]

What do you mean by saying there was no change? If you fulfil one of the three suggested solutions, there should be no warnings about that anymore and you should see correct shading of affected material in your renderings. And no, incorrect gamma of normal maps shouldn't affect rendering times. Well, certainly not to such degree.

[Lnt]

Unfortunately the warning was still there even after i deleted and added a new Corona Normal with a Bitmap ( loaded the map with 1.0 gamma  and enable the Add Gamma to input in normal map )
But eventually i deleted the model which was causing this issue, and now i get no more warnings.

However the render time is still very high compare to previously.
I can't figure out why the render time is so big now, since i actually fixed the portals to cover every opening perfectly, and i fixed every white shading with Albedo.
Is there a common mistake that i could've done to increase the render time so drastically? the settings are default

[romullus]

Warning will stay even if you fix a problem. You need to manually clean CEM window and warning messages shouldn't reapear, that is if you fixed given problem. I had requested that Corona should recognise obsolete warnings and automatically would delete them, but my request was declined. Can't recall exact reasoning, though.

As for long render times, it's hard to tell without having actuall scene. Does your windows has glass? Sorry if it was asked before - don't have time to re-read whole topic now.

[Lnt]

I manage to get rid of the error by removing the fault model completely.

As for the render time, you actually pointed out something that i forgot. I had 2 "planes" of glass for my windows and i also forgot to check the Thin option on the glass material. I just did and the result is huge, thank you very much.

I also have a side question that might be more max related then Corona, but: how can i export a single material or a single 3D model out of my scene? So far if i want to extract a material or model i simply delete everything else and save the remaining model/model with material with a different name.

[romullus]

I manage to get rid of the error by removing the fault model completely.

I wouldn't call it a solution then. You could select your model and in slate editor press material>get from selected. You should get actual material that is applied to that model, then you could inspect that material and see if it contains wrong map.

As for other questions. You can save individual models or groups by selecting them and pressing save as>save selected. It will save only selected models and will leave all render settings intact. However often it will save many unnecessary things like unused maps and other invisible garbage that was present in old scene, so i prefer just merge needed objects into new scene.

Materials can be saved in material libraries. You can read more about that in max help.

[Lnt]

I did change the normal and the maps of the material causing the issue, but it didn't help at all, so the only option was to delete the model since i really need to start this render.

There another thing i don't understand about Corona. It seems to be very "random" when it comes to final renders ( 3000+ px )
I use 2 PCs to render, ( not DR ) both have the same 3ds max and the same demo version of corona installed, one is an older model of Xeon E3, the other an i7 4790 i think( which is should be better ) both 8gb ram. I render exactly the same 3D since i work on a google drive folder, yet the render time is acting weird.

Currently exactly the same 3D on Xeon took 4 hours with 120 passes, on i7 after 4 hours it has 12 passes and it looks like a 5 minute render on the xeon.
And sometimes on the i7, closing and reopening the same exact 3D causes a totally different time of the render.
Yesterday, i left this i7 overnight, and in 12 hours i had a very noisy result, then i simply closed and reopened the model and simply pressed render. In 5 minutes it produced a better render then the 12 hour one. The xeon seems to be more stable.

I did a huge progress on Corona since i start working with it and with help on this thread, im just trying to understand it better, its really a great engine.

Sorry for the long posts.

[romullus]

Something is causing problems on your i7 machine. Are you getting any error messages, like FHT or low memory?

[Lnt]

I always get low memory, on both PCs, they have only 8gb.
I removed the FHT for 3dsmax.exe on both PCs.

The main confusion about this is how random the render time is sometimes. I understand that my PCs aren't that great, but why the such a behavior difference between the renders.

[Lnt]

Unfortunately i have to come back to this thread because the render on my i7 doesn't want to go above 3 passes. After 3 hours is as noisy as it was after 30 minute and still has 3 passes.
The same model on Xeon reached 142 passes in 5 hours.
I have no idea what to do.

[maru]

Hi, some time ago I advised you to start a support ticket (https://coronarenderer.freshdesk.com/support/tickets/new) - have you done that? If yes, then what is your nickname/email in the support portal? If no, then please do it. This is the best and most convenient way to debug such problems.