Author Topic: Material is changing colour in render  (Read 6683 times)

2019-07-25, 01:52:15

Tanya_00

  • Active Users
  • **
  • Posts: 12
    • View Profile
I have an acoustic panel (a felt -like material) in my scene. It is a really dark green colour. What I found is when I want to brighten up a scene or increase intensity of the lights the panel changes colour to bright green (misrepresenting the actual colour). Please see attached image.  I don't think this effect would happen in real life. Doesn't matter how much light I would shine on the panel it would still remain dark green. Would anyone be able to help me? I greatly appreciate it.

2019-07-25, 08:40:24
Reply #1

sprayer

  • Active Users
  • **
  • Posts: 780
    • View Profile
that's where you need post processing and use masks


2019-07-25, 15:25:36
Reply #2

maru

  • Corona Team
  • Active Users
  • ****
  • Posts: 10186
  • Marcin
    • View Profile
Why wouldn't a material become brighter as more light is cast onto it? Do you have some kind of real-life reference that would confirm this?

2019-07-25, 17:20:33
Reply #3

dzintas

  • Active Users
  • **
  • Posts: 26
    • View Profile
This should be expected behavior. Just setup your exposure and lights then adjust your material to desired effect. Or use corona ToneMapControl node.

2019-07-25, 20:25:52
Reply #4

Hilmar

  • Active Users
  • **
  • Posts: 14
    • View Profile
not sure if I got it right.... your problem is the dark green, that does not get lighter, although you crank up the light, right?
Are you using an overridematerial or a rayswith? Maybe the object is excluded from your light? Is the rest getting lighter? Are the normals facing out? 

Hilmar

2019-07-30, 14:46:51
Reply #5

Tanya_00

  • Active Users
  • **
  • Posts: 12
    • View Profile
Hi All, thanks a lot for your suggestions. I will try the mask and Tonemap control mode and see what works better.

To answer Maru's question, I do agree that the material should light up some when it is close to a light source and change its tonal value (?).  But it seems like it my render it becomes a different hue (a much brighter green) when it is close to the light. I may be wrong...
Here is the acoustic panel I would like to use. Please find attached. You can see it is lighter on one side (you can see that it is actually green) and almost black on the other (on the side that is further from the light source). But there is no bright green in there...

Thanks again :)

2019-07-30, 16:37:30
Reply #6

sprayer

  • Active Users
  • **
  • Posts: 780
    • View Profile
that's  because real material have micro holes what absorb light, but in 3d it is useless to make so small detail you can try rayswitch material for that and override darker material for GI, this is also recommend for bright material close to light to avoid much noise

2019-08-08, 15:55:40
Reply #7

Tanya_00

  • Active Users
  • **
  • Posts: 12
    • View Profile
Thank you! I will have a look into this as well.

2019-08-08, 17:00:17
Reply #8

Juraj

  • Active Users
  • **
  • Posts: 4116
    • View Profile
    • studio website
Tanya isn't wrong when she says materials don't get so much more saturated and hue-changed with higher saturation, it's been discussed that the Reinhard tonemapping (Highlight compression) that Corona uses doesn't resemble how cameras capture reality.

Not sure why Rayswitch in GI was suggested...the issue is how the material looks, not what light it casts. Best trick for consistent colors would be if Corona's 'CoronaMix' node featured "Color" mode from Photoshop, that was nested inside 'Tonemap control' so that HSL never changes and that color was on top of greyscale (or highpassed) albedo.
I am writing this complicated nonsense here just in case someone wants to lobby in Request thread to include more modes into CoronaMix ;- ). It's still lacking at least 4-6 from Photoshop.

Simple solution for now:
- Make the Diffuse color actually darker than you think it is. The true physical color of something before lights and reflection adds up is often quite different.
- Have good bump map and use correct reflection (Full white color 255/255/255 and IOR 1.52). Then adjust roughness until it looks like in reality. The reflection will desaturate your material as you will increase exposure. So it will never become so toxic.
- Last step, as I said in first sentence, Corona "renders" colors wrong when they near highlights. In Photoshop, add new Vibrance/Saturation layer with empty mask. Click on the mask, Click on 'Select'/'Color Range' from top menu, then select 'Highlights mode', set the 'Range' value somewhere between 220-255 and 'Fuzziness' until you get nice gradient that covers highlights of your image. Then use negative Vibrance (not saturation) until it looks better and you get rid of any toxic colors.
talcikdemovicova.com  Website and blog
be.net/jurajtalcik   Our studio Behance portfolio
Instagram   Our studio Instagram, managed by Veronika

2019-08-14, 12:26:16
Reply #9

maru

  • Corona Team
  • Active Users
  • ****
  • Posts: 10186
  • Marcin
    • View Profile
Maybe using filmic highlights/shadows in the VFB post could help too?
I guess to get "correct" results, similar to what happens in real life, we would need some kind of advanced "velvet-like" shader?

2019-08-14, 12:31:31
Reply #10

Juraj

  • Active Users
  • **
  • Posts: 4116
    • View Profile
    • studio website
Maybe using filmic highlights/shadows in the VFB post could help too?
I guess to get "correct" results, similar to what happens in real life, we would need some kind of advanced "velvet-like" shader?

'filmic highlights/shadows' is just broken, nobody please touch this :- ). We should just get rid of it finally and make real filmic.

We absolutely need fabric shading. It's all there, 'Sheen' parameter in the big PBR renderers like Pixar Renderman.

Cautiously waiting for both for years.
talcikdemovicova.com  Website and blog
be.net/jurajtalcik   Our studio Behance portfolio
Instagram   Our studio Instagram, managed by Veronika

2019-08-15, 14:22:08
Reply #11

maru

  • Corona Team
  • Active Users
  • ****
  • Posts: 10186
  • Marcin
    • View Profile
'filmic highlights/shadows' is just broken, nobody please touch this :- ). We should just get rid of it finally and make real filmic.
How exactly? Do we have some good description of the issues with it?
What I found out (just visually in a few random scenes) was that filmic highlights and shadows both set to 0,8 look similar to Dubcat's photographic LUTs.

2019-08-15, 17:26:00
Reply #12

Juraj

  • Active Users
  • **
  • Posts: 4116
    • View Profile
    • studio website
I thought it was common knowledge and well agreed it works completely wrong : /. At least for two years.

Well, I'll make a new thread about it later then. The tonemapping is really holding Corona back.
talcikdemovicova.com  Website and blog
be.net/jurajtalcik   Our studio Behance portfolio
Instagram   Our studio Instagram, managed by Veronika

2019-08-16, 11:51:33
Reply #13

maru

  • Corona Team
  • Active Users
  • ****
  • Posts: 10186
  • Marcin
    • View Profile
I thought it was common knowledge and well agreed it works completely wrong : /. At least for two years.

Well, I'll make a new thread about it later then. The tonemapping is really holding Corona back.

I think it was discussed indeed, and the devs are aware of it, but it won't hurt to start a new thread with nice explanations and examples. Thanks! :)