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Messages - GeorgeK

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Hi I don't believe this is a Corona issue, seems like a 3ds max inconsistency. After meddling a bit, my regular bitmap returns worse quality in the viewport.

You might also want to try altering CoronaBitmap interpolation and refresh the material in the viewport.

Lastly can you please clarify if you are using any corona-texmap nodes after Corona bitmap?

Hello Romullus,
Thanks for your response.
I uploaded the demo scene:

Successfully uploaded as


Thank you for submitting the scene, I am afraid I wasn't able to reproduce the issue the images render the same with each new render. Some things to consider.

  • On the scene file you are showcasing the issue, is it possible that there are faces overlapping each other and with each render you get a different face to render?
  • Make sure all of your textures don't have identical names, like f.e. "diffuse_pic_01" the same name shared for two different images. In the file you've shared with us I know that's not the case.

[Max] I need help! / Re: Roughness vs Glossiness in Corona 7
« on: 2021-07-23, 14:40:20 »
Don't use Corona color correct node to invert map, use standard output node instead. The former is inverting in sRGB space and the latter does that in linear space, which is what you need here.

I guess that's something that needs a note or clarification on the helpdesk article for CoronaPhysical mtl, thanks for pointing it out.

[Max] I need help! / Re: Light visibility in viewport
« on: 2021-07-22, 14:51:07 »
Got it. I’ll write a sticky. Do you know if this has been reported as a bug?

Thank you for reporting this, this is highly likely a bug, reporting it for further investigation by the dev. team.

(Report ID=CRMAX-833)

[Max] I need help! / Re: shadow amount
« on: 2021-07-22, 13:48:41 »
Why is it when the only thing I change from the default values is the shadow amount and save a png, the shadows look the same? Do I need to changes something else?
thank you

Hi, the Shadow amount parameter controls how much light is bounced off the shadow catcher onto other objects in proximity, increasing the value will force the shadowcatcher object to bounce less light, thus making shadows look darker.

A small example here is where the shadow catcher has a 3.0 amount against one with 0.1, the light source is directly above:

[Max] I need help! / Re: Round Edges Map - Physical Material
« on: 2021-07-22, 12:41:01 »
Apologies if already asked but cant find it in the search.

If you were making a material with a clear coat would you put corona round edges map in the base layer, clear coat layer or both?

Thank you in advance

Hi RenoJ, Corona Round edges will mostly work with the base bump in a case where you want two or more surfaces to look uniform/welded , but there are also cases where you'll need to apply it for both bumps, like f.e. a box or cube that needs to have its edges chamfered through the use of corona round edges.

Hello, new user here. I m downloading one material from quixel megascans but don't know what represents reflect map on their downlaod list (picture attached)?
Normally when I use Corona I only use bitmaps for diffuse/albedo, reflect, gloss, normal and displacement. Their download list is either missing reflect map or is it called something else over there?

That would be a specular map but it needs some treatment in order to be used for IOR, I would suggest using their bridge plugin it does a pretty good job converting their presets into Corona legacy material. If you are considering on using CoronaPhysical then the entire process is much easier with a single roughness map or Spec to IOR mode.  If you require any further assistance on this please don't hesitate asking.


In terms of physical correctness, the previous implementation allowed for non physically plausible results, you cannot have a single surface that's rough but also highly glossy at the same time.

That reminds me, does it now work if we apply different treatment (through material ID for example) to refractive glass (with real volume/thickness) ? Most frosted glass is simply sandblasted on one side and polished on other (when it's not glued to hide the sand-blasting in middle).

I remember this always created some kind of artifacts.

I believe it's doable with no issues but, I ll try it out :).


How do you deal with flossy refraction (not reflection) with the new PBR material ? In legacymtl, you have the glossiness in the refraction, but it seems to be different in the new pbr materials.


In terms of physical correctness, the previous implementation allowed for non physically plausible results, you cannot have a single surface that's rough but also highly glossy at the same time.

To achieve a form of coated frosted/etched(even sandblasted) glass you simply have to enable clear coat within CoronaPhysicalMTL, here is an example of a coated/non-coated lamp with base roughness 0.9. :

I hope this helps.

Today I noticed for the first time a difference in reflections when I changed the roughness IOR from 0.00 to 0.01.

I am not sure if this is already known. So sorry if this is a double post.

Simple reflective plastic material is used with no clear coat.
Everything looks fine at IOR 0.00. Once it goes above 0.01, the reflections change. It reminds of switching the reflection mode in UE4 from nonRT to RT.
Normally this wouldn't bother me at all, but I very often use a value of 0.00 to get softer highlights like from the sun. So almost all my materials are at 0.01. But this example shows why I had problems when creating my physical materials.

Please focus on the BMW badge.

Did more tests and I can narrow down the cause a bit. The material does reflect an HDR in Dome mode. When the mode is set to Spherical everything is fine.

In Dome mode it seems that the lower hemisphere is displayed as black for materials with a Roughness of >0.01

Updated with new images showing the issue with dome mode.

This was a known issue and I believe it's already addressed, unless I am missing something. Which version of Corona DB or RC you are using in these examples?

(Report ID=CRMAX-436)
Dome - (Internal id=311287120)

Hi, apologies I don;t think I can upload the scene due to Project NDA.

The GPU hardware I use is Zotac 2070 Super

Is it possible that you reproduce the issue in a non-NDA scene, or offer some reproduction steps?


Sent you the team's compiled list of feedback :)

Once again thank you very much for the detailed feedback. Marcin is on it :).

In your freshdesck website you have considered:

0.70 μm for Red, 0,55 μm for Green, 0.45 μm for Blue

But for wideRGB gamut like that:

Green belongs to 0,52 and blue 0,390. why is there this discrepancy?


I don't believe input values can be absolute, most approximations around the limits of the visible light spectrum will work just fine depending on, as said previously, "preferred visual outcome and on how much oxidation is introduced on the metal's surface" (excluding metal alloys - impure metals - although oxidization implies impurity, but let's just leave it at that).

Let's take the example of Pure Gold (Au) -  Generally, its electrons move at relativistic speeds (especially on its outer surface). The outer surface is responsible for its chemical behaviour and a lot of physical properties, including color. The human eye spectrum varies from wavelengths - approximately 390 nm (blue) to 700 nm (red), gold absorbs a lot of the low wavelengths (blue). So we’re left with the opposite (yellow - towards red when it's pure).

Pure Gold (au) does not get oxidised, hence pure gold should not appear green-ish, it should mostly reflect yellow with a minuscule tint of red. The following comparison showcases exactly just that, Complex IOR of Gold with 0.7-0.55-0.45 against sRGB limited values of 0.61-0.56-0.47: (Both outcomes can be described as Gold, but when thinking of recreating Pure Gold we should compensate for corresponding wavelength inputs, in order to remove the greenish tint)

So, to summarize, any approximations between 0.70 μm for Red, 0,55 μm for Green, 0.45 μm for Blue (~ +- within reason) will work great for most pure metals, in some cases, you might want to experiment with different wavelengths. I hope this helps, and it actually makes sense!

Rc4 Error.
tested in several scenes!

Please submit a ticket, consider archiving a scene where the issue is reproducible for you and if possible include your 3dsMax minidump produced after the crash. For submitting a ticket please check the link on my footer below.

Thank you

Hello, how have you decided the wave values ​​for RGB that are put in the complex IOR that appear here -coronaphysicalmtl-? Shouldn't they be equivalent to the ends of the sRGB triangle where Red corresponds to 0.65nm for example? (see link of the image)


Hi n2graf, please note that Corona is using color space with a wider gamut than sRGB, you will also find that approximations around 0.7-0.55-0.45 can produce a more favoured outcome depending on how much oxidation is introduced on the surface, and the type of metal.

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