Problem with views from model are either too dark or too bright

[caezar]

I am having a hard time to get nice images from my 3d max model using corona renderer which I believe because I am not expert in 3d Max. views collected from my model are varied from very bright to very dark as the exposure EV parameter goes fro 0 to -5. I have been advised to set the Exposure EV parameter to -2 or -4 because the scene is an outdoor scene. However, I think there is something missing here and I suspect its the lighting. I will attach the views that I collected via GUI rendering and Maxscript because I use MaxScript the most as well as the MaxScript used.

I will appreciate it if someone has any idea about this problem
I am running 3D Max 2019 and Corona 3.

[romullus]

There's nothing wrong with EV, if you'll set it to lower values, you'll get darker image and vice versa - higher EV will give you brighter image. That's how exposure works. On the other hand, i think there is big problem with your lighting setup. That giant light ball near the ground... is this supposed to be your sun? Corona has dedicated sun light object, which will give you physically accurate lighting. It can work with procedural Corona sky or with HDRI enviroment light.

I would recommend you to go to official Corona youtube channel and watch tutorials about scene setup and lighting. You can start with these:

list=PLt4UrWcQaAX_cwRESX7FYH7nNM5ZT-WzT&index=28&t=0s

list=PLt4UrWcQaAX_cwRESX7FYH7nNM5ZT-WzT&index=3&t=0s

[caezar]

Thanks for your help.
Basically, I removed the big ball to make sure everything is OK.
Next thing I tried to follow the two videos and here are the problems:
1- The difference in quality between the images in the interactive Rendering and hence the rendered Image and the saved one.
2- the overall quality of the images from the model is not that good comparing to Vray performance.
3- Images are still suffering from either too dark or too bright.
I am attaching the images I did collect under different circumstances: I have added a corona sun to the model based upon the videos and get images when there is only a corona sun and with corona cun and corona sky ( environment).

Am I missing something here as the images look not that good. I will attach all the images here

[romullus]

First of all, you should always use enviroment light, either HDRI or Corona sky or in some cases even plain white colour might do the job. Also, you shouldn't be fixated on some specific EV values - there's no single EV that fits all scenes. Simply drag EV slider untill you will see that your scene is not too bright and not too dark. It does'nt matter if rendering is in progress, or already stopped, you can always adjust EV interactively.
I noticed that your sun is located directly overhead. Unless you're trying to replicate lighting conditions in equator on noon, you should lower sun's angle considerably to get more realistic and more pleasing to eye lighting.

[sprayer]

You may share the scene so we can take a look.
Did you check environment dialog to make sure exposure control disabled?
About quality IR you mean displacement? It calculates at start rendering, if you rotate camera in IR you will see displacement only from starting view angle

[PROH]

Hi. I second everything that romullus said. I also noticed that you're talking about differences between the rendered image and the same image when saved to disk. If there's any difference in such case, then it's caused by saving the image with wrong gamma (f.ex. jpg Beaty should be saved with gamma 2,2).

[caezar]

@romullus, thanks a lot for your helpful notes. I just want to clarify some of the things in your reply:
I was careful when posting the images to show the effect of variable EV with and without corona environment light. Moving EV from -4 to -2 is showing how the image brightness changes from too dark to too bright so I guess the perfect EV is within this range, therefore I used those images as an illustration of the problem.
I did notice that there is no proper lighting in the scene and that's why I used Corona environment light which enhanced the collected images but still not so regular quality images.

Regarding the noontime, I purposely set up the sun so that I can get maximum brightness in the scene for comparison.


@sprayer, I am happy to share the scene.

https://drive.google.com/file/d/1Rcm3_D0mjdGn1m5cNzau1gXP6k0NWGj5/view?usp=sharing
here is a link for the scene please do have a look and tell me if I am doing something wrong.
Ps, there are a couple of map files in the subfolders.

@PROH thank you for your reply, I already have Gamma set to 2.2 and enable gamma/Lut Correction box is ticked .

thank you all for your reply
and I am grateful for your patience and understanding.

[sprayer]

It looks fine to me, there is some problems in your scene, scene infected with "virus" ALC.
You need to fix normal map gamma with corona converter. And do not need to render exterior with UHD. Also you have render elements from vray.
But scene light is fine, corona sun+sky and EV -4 good for starting exterior scene.
But you need to check materials, asphalt for example have too much glossiness and looks wet also have big scale


https://i.imgur.com/SO7EA4C.jpg

I was open in corona 4.1 maybe some settings was reset

[caezar]

@sprayer
firstly, thank you for your informative reply.
I have followed your advice, installed 3D max security tools which removed the virus, tried secondary solver as path tracing and none instead of UHD cache, removed the Vray elements in the scene and tried the Corona converter to fix the normal map. Although when using the corona converter ( Start Conversion) nothing happened compared to the tutorial video by Corona, I think its already set based on the startup screenshot attached here.
despite all the above the quality of the output image has been improved.
May I ask you if the image attached in your reply was from the IR or it was the image saved on the desk? because I get same image quality in IR but when I save them on the desk it degrades significantly quality-wise.
thanks again for your time and help again.

[PROH]

Your Bitmap output gamma is set to 1 in your file. Use the system settings instead.

[sprayer]

Yes material was converted and you need just to click on Fix CoronaNormal gamma.

At opening i choose to keep system gamma for bitmap 2.2.

I did not save image on disk, just copy to clipboard from IR menu and paste it in program for uploading image on image host.

I am also have problem with colors but in my case it's bug in all chromium browsers

[caezar]

Thanks alot @PROH
 it does work now.

May I ask you how to do that in MaxScript?  as it only working now with GUI mode?
I tried to save the model with those settings and use the MaxScript but still giving me the same old result ( Bitmap output gamma=1).

I also looked at the available functions of Corona scripts but No chance so I assume its more related to 3D max scripts' functions

[caezar]

Thank you @sprayer
I thought using the model setting would be better rather than keeping the system settings.

[romullus]

Paste

Code: [Select]

FileOutGamma = 2.2 line in maxscript listener. It will set bitmap output gamma to 2.2

[caezar]

thank you @romullus

I think I figured out the problem now, it seems that using the Corona compatible line :

[renderers.production=CoronaRenderer()]
[/renderers.current.colormap_additionalGamma=2.2]

 is not working as now I am getting this error :
'3ds Max is configured to use incorrect gamma X. Value of 2.2 is required for correct output'