The new Corona Converter feedback thread

[OH_BOY]

+1

[selene]

The RC 6 version of the converter constantly badly detects metal / non-metal materials when converting, Very annoying situation, e.g. in the case of many objects, such as books .Link to the scene after converting, original vray materials in the editor  https://drive.google.com/file/d/1QV2Bx3_FdbIcoBxPBFkn4r9vbNAEY-mY/view?usp=sharing

Hello Skalpel3d. Thank you very much for your feedback. To be honest the metal / non-metal detection was probably one of the most difficult things to implement in Corona Converter, since CoronaLegacylMtl has no "metalness" parameter (and for a long time also VRayMtl had not "metalness" parameter), therefore there is no "clean" / "exact" way how to determine whether the original material was intended to represent a metal or not. As a result, Corona Converter can only make some "educated guess" based on available parameters which sometimes unfortunately leads to false negatives or false positives. We are aware of this limitation and we are already working on some improvements, however we decided not to include them in V7 anymore, since it will require huge amount of testing to make sure the new heuristics works better in all / most cases than the current one. Once the testing will be finished, we'll include these improvements to Corona Converter bundled with Corona Renderer 8 daily builds.

[kino_unico]

in addition to detecting false metals, when you manually convert from metal to non-metal it creates an IOR value: 1.01 the problem is that if you had written that value down, you have to manipulate it again.

[selene]

Thank you!
RC7- now the shader tree looks much simpler and reasonable. No more unnecessary Mix maps - that's good :)! (Converter7_vray-corona_mat-structure_RC7.jpg) and rendered result is visually the same as it was with RC5 and close to original look of the shaders (Converter7_vray_original-converted_mat-RC5-7.jpg)
This time material structure is much cleaner for further work with it which is great, now I understand how almost all maps were converted in order to use all aspects of Vray 2sided material within single Corona Physical material using FrontBack maps (Converter7_vray-corona_mat-structure_RC7-1.jpg), but:
1. could you explain, please, the meaning of use maps in Vol. adsorption and Vol. scattering of leaf material and why the map which was used in Vray material to map translucency (Map #11) is used here, not in translucency slot of Corona Physical material (Converter7_vray-corona_mat-structure_RC7-3.jpg)?
2. Why IOR parameter of the trunk material is mapped with some Mix map? Is it the way to imitate mapped reflection parameter of Vray material (Converter7_vray-corona_mat-structure_RC7-4.jpg)? And would be interesting to know about the usage of CoronaColor map with applied Solid HDR color higher than 1 in IOR mapping, like IoR map from this example has.

Also would be interesting to hear what do you think about the way of conversion of Vray 2 sided material which I used in my experience. I used two Corona materials plugged in to Corona Layer material with Corona FrontBack map used as mask. Here is a very quick example of this kind of conversion (Converter7_converted_mat_RC7-layerd_2sided_mat_strc.jpg). Material structure is pretty simple, render results you can see also here (Converter7_vray_original-converted_mat-RC7-layered_mat.jpg and Converter7_converted_mat_RC7-layerd_2sided_mat.jpg)

Hello Bormax!

Answer to question 1:

The same phenomenon which is defined by Translucency Fraction parameter in CoronaPhysicalMtl is defined by Translucency color in VRay2SidedMtl (not by VRayMtls' parameters connected to the VRay2SidedMtl).

The Map #11 is not used in Translucency color slot of CoronaPhysicalMtl, because VRay2SidedMtl automatically uses base color of the opposite side as a translucency color (that's why we pick Map #10 and Map #16).

CoronaPhysicalMtl ignores both Volumetric Absorption and Volumetric Scattering parameters when its Thin-shell parameter is enabled, but Corona Converter always propagates all maps from the original material, even when they do not contribute to look of the converted material. If VRayMtl uses some other Translucency modes - e.g. SSS, we plug the corresponding maps to these slots so we decided to do the same in this case to be consistent.

Answer to question 2:

Because the original VRayMtl uses reflection amount parameter / reflection amount map, however this parameter is not physically plausible (that's why it's not present in CoronaPhysicalMtl). Since the only CoronaPhysicalMtl's parameter which may affect its reflectivity is IoR (if the material is not metal), we try to create a new IoR value by decreasing the original material's IoR using the reflection amount parameter / reflection amount map in order to preserve look of the original material. However note that this is a "hack" created to preserve look of the original materials. Alternative (more strict) method would be to ignore / drop such parameters / maps, but this could lead to many look-breaking changes during the conversion.

Answer to question 3:

To be honest I have never tried this before, but it looks like a good idea :) May I ask you whether the results look identical? And which approach leads to better render times?

[Bormax]

Hello Bormax!

Answer to question 1:

The same phenomenon which is defined by Translucency Fraction parameter in CoronaPhysicalMtl is defined by Translucency color in VRay2SidedMtl (not by VRayMtls' parameters connected to the VRay2SidedMtl).

The Map #11 is not used in Translucency color slot of CoronaPhysicalMtl, because VRay2SidedMtl automatically uses base color of the opposite side as a translucency color (that's why we pick Map #10 and Map #16).

CoronaPhysicalMtl ignores both Volumetric Absorption and Volumetric Scattering parameters when its Thin-shell parameter is enabled, but Corona Converter always propagates all maps from the original material, even when they do not contribute to look of the converted material. If VRayMtl uses some other Translucency modes - e.g. SSS, we plug the corresponding maps to these slots so we decided to do the same in this case to be consistent.

Answer to question 2:

Because the original VRayMtl uses reflection amount parameter / reflection amount map, however this parameter is not physically plausible (that's why it's not present in CoronaPhysicalMtl). Since the only CoronaPhysicalMtl's parameter which may affect its reflectivity is IoR (if the material is not metal), we try to create a new IoR value by decreasing the original material's IoR using the reflection amount parameter / reflection amount map in order to preserve look of the original material. However note that this is a "hack" created to preserve look of the original materials. Alternative (more strict) method would be to ignore / drop such parameters / maps, but this could lead to many look-breaking changes during the conversion.

Answer to question 3:

To be honest I have never tried this before, but it looks like a good idea :) May I ask you whether the results look identical? And which approach leads to better render times?

Hello Selene!

Thank you for so detailed answers! Now it's clear for me how converter works in this case. Great!

As for the way I used to convert Vray 2sided material, I've done some quick tests. Basically I've used converted by Converter original Vray scene, pictures of single tree and small forest made with Forest Pack. Adaptivity ON, noise limit 4%. Here are results:

Converter7-single_tree_converter.jpg - Passes 25, rendering time 1.38
Converter7-single_tree_manual.jpg - Passes 25, rendering time 2.24
Converter7-FP_converter.jpg - Passes 115, rendering time 14.25
Converter7-FP_manual.jpg - Passes 110, rendering time 23.15

Material structure is a bit more clear and easy to control in manually converted version, but rendering time grows really much. But if you want to test it yourself, I've uploaded scene with private uploader, there you can find all 3 types of materials assigned to different trees and forests.
1627342416_converter7-vs-manual-2sided.zip

Edit:  1627358880_converter7-vs-manual-2sided.zip

[INVIZ]

Installed offical 7 release... My converter saying 2.0??? That normal? not converting properly

[rowmanns]

Installed offical 7 release... My converter saying 2.0??? That normal? not converting properly

Hi,

That's the correct converter version. What is not converting properly? Do you get some error?

Thanks,

Rowan

[INVIZ]

Installed offical 7 release... My converter saying 2.0??? That normal? not converting properly

Hi,

That's the correct converter version. What is not converting properly? Do you get some error?

Thanks,

Rowan

Vray2sidedMtl not converting, nor vray lights.. was fine on corona 6

[INVIZ]

No errors from what can see

[selene]

Vray2sidedMtl not converting, nor vray lights.. was fine on corona 6

Sorry to hear that INVIZ. Please could you send us the scene which manifests this problem?

[maru]

Installed offical 7 release... My converter saying 2.0??? That normal? not converting properly

Hi,

That's the correct converter version. What is not converting properly? Do you get some error?

Thanks,

Rowan

Vray2sidedMtl not converting, nor vray lights.. was fine on corona 6

I am guessing it could be too old V-Ray version. You need V-Ray 4 or newer. It doesn't have to be purchased or activated, just installed.

[INVIZ]

Installed offical 7 release... My converter saying 2.0??? That normal? not converting properly

Hi,

That's the correct converter version. What is not converting properly? Do you get some error?

Thanks,

Rowan

Vray2sidedMtl not converting, nor vray lights.. was fine on corona 6

I am guessing it could be too old V-Ray version. You need V-Ray 4 or newer. It doesn't have to be purchased or activated, just installed.

I see, so I installed demo of lastest vray.. now cannot see or select corona renderer in choose renderer??

[maru]

I see, so I installed demo of lastest vray.. now cannot see or select corona renderer in choose renderer??

That's definitely not expected... Can you try reinstalling Corona 7?

[INVIZ]

I see, so I installed demo of lastest vray.. now cannot see or select corona renderer in choose renderer??

That's definitely not expected... Can you try reinstalling Corona 7?

Tried that first, tried uninstalling, then deleting all files.. no luck..

Then uninstalling 3ds max, clean install, clean install of corona 7... still nothing. going nuts D: Mid project and 2 days gone going round in circles.

[maru]

I see, so I installed demo of lastest vray.. now cannot see or select corona renderer in choose renderer??

That's definitely not expected... Can you try reinstalling Corona 7?

Tried that first, tried uninstalling, then deleting all files.. no luck..

Then uninstalling 3ds max, clean install, clean install of corona 7... still nothing. going nuts D: Mid project and 2 days gone going round in circles.

Sorry about that. Please try following this guide step by step:
https://coronarenderer.freshdesk.com/support/solutions/articles/5000694496

If it doesn't help or you are having some difficulties, please contact us here https://coronarenderer.freshdesk.com/support/tickets/new and we will assist you ASAP.