Corona 12 crashes all previous Coronas

[Stan_But]

Hi,
do you know about the big problem that when trying to open a max file with Corona 12 in the 3dsMAx with Corona 11 or earlier than the 3dsMAX has been crashed? At the same time when re-save the scene with Corona 12 mats with set Product render as any other than Corona, Scanline for ex., than the scene will be open fine in the 3dsMax with Corona 11 or earlier.
Looks like there is the some conflict inbitween code of Corona 12 and other Coronas main menu.

[TomG]

I am not 100% clear what you mean - is it that a scene saved with Corona 12 will not open in Corona 11 and earlier? If so, forward compatibility like that is not guaranteed, only backward compatibility (ie you can open a scene from Corona X in Corona X+1, X+2 etc, but there is no guarantee you can open the scene from Corona X in Corona X-1, X-2 etc.)

This is because sometimes the data structures etc. change so much that earlier versions of Corona have no way of understanding them. As such, any errors when trying to open a scene saved with Corona 12 as the active renderer when Corona 11 or earlier has been set is the active renderer is not a bug, nor something we can fix (basically, the "old" version of Corona would have needed to know what was going to happen in the future with changes to Corona, and time travel is not one of our abilities ;) ).

As a note, if Corona is not the active renderer on saving the scene, then yes, the Corona data structures won't be saved (for things like tone mapping, lightmix, Corona Materials, etc. as the non-Corona engine won't understand or know about those) which means it might open in an earlier version of Corona - but all the Corona specific settings will be lost.

If you mean something different from the above though, let us know!

[Stan_But]

Hello,

Yes, its exactly about the Corona 12 crash affecting all earlier versions of  Corona. It would be very cool if it would worked as it did before - you just needed to reset F10 Corona render settings - and it was all.

But now it just leads to full crash of 3dsMax. And the only way to avoid this - its to change the current render and loosing all the global settings.

Its too sad if its impossible to fix. Because of these crashes all sites of models placing cant normally work with Corona 12 and have to reject such scenes and it doesnt help to popular of Corona 12 amomg model makers.

[Avi]

so, the crashes are very specific to a file which was made using earlier version of Corona? Is it possible for you to send us that file by starting a ticket here: https://support.chaos.com/hc/en-us/requests/new

[TomG]

Other way round Avi, a file made in new Corona crashes old Corona :)

Thing is, Corona 12 had significant changes to the VFB, tone mapping, automatic exposure, lightmix, and more. This is why it isn't as simple as F10 to reset settings, as there are things that the old Corona just know what to do with.

BTW, rather than "change to a different render engine and export", you can just save with Corona and try merging the new scene into the old version of Corona rather than loading it, because then Corona shouldn't try to read all the new things it doesn't understand (though you may still lose some settings, parameters, features, etc. in doing so).

If someone is making models to share (rather than scenes), it should be less of an issue than for sharing a whole scene, and they can carefully avoid using any new features to maximize the chance that it can be merged into an old Corona.

Beyond that, they'd then just make the judgment call - do they want to take advantage of new features in the latest version of Corona getting some results that couldn't be achieved any other way while narrowing the users who can use it, vs. do they want to maximize who can use it but give up on some new features that could make the model/scene better, and based on that choose to develop the model in an older or newer version of Corona (the multiloader makes it easy enough to be able to run Max with different Corona versions, so no need to be installing and uninstalling all the time).

The only way to "fix" it would be to stop working on Corona 13 or 14, and go back and edit code in 11, 10, 9... where would we stop too? Since development time is limited, that isn't going to happen (and indeed no software I know of does this).

[maru]

We have never ever supported this, it isn't possible due to technical reasons.

[Stan_But]

Hello, thanks you all for your attention to the issue.
I've got that the conflict attempt with two elements of the Corona Tone Mapping: the Lift Gamma Gain and the White Balance. If they are removed from the Tonemapping stack then everything works well and you can open scenes with Corona 12 in the 3dsMax with previous Corona.

Does it need to create the ticket or the theme is closed with it?

[TomG]

No need for a ticket as there is no bug or problem here - it is the expected result of new parameters being added in a new version of Corona, which means old versions can't open the file. Quite natural :)

[agorbachev]

Hello,

Yes, its exactly about the Corona 12 crash affecting all earlier versions of  Corona. It would be very cool if it would worked as it did before - you just needed to reset F10 Corona render settings - and it was all.

But now it just leads to full crash of 3dsMax. And the only way to avoid this - its to change the current render and loosing all the global settings.

Its too sad if its impossible to fix. Because of these crashes all sites of models placing cant normally work with Corona 12 and have to reject such scenes and it doesnt help to popular of Corona 12 amomg model makers.

Thanks for the interesting solution — we hadn’t seen it before, but we’ll definitely give it a try!

Hey corona team! 👋

We also wanted to share something important for the Corona team: if someone accidentally updates to Corona 12.1 or 12.2, they won’t be able to open the same scene in earlier versions (we tested with Corona 11).

We were a bit surprised to see so few discussions about this on the forum. When we ran into the issue, we expected it to be widely known and perhaps already resolved — but apparently not. In fact, our entire team encountered it.

The tricky part is that Corona becomes incompatible with all previous projects. So if just one artist updates, the whole team is forced to switch versions, regardless of where the current projects stand.

So, friends — if you’re planning to update, do it with caution.

By the way, based on our experience: if you merge the scene into an older version without the CoronaCamera, the global crash and 3ds Max shutdown don’t happen. In all other cases, it crashes every time.

Hope this helps other users — and maybe the Corona team — to improve future compatibility!

[TomG]

As mentioned earlier in this thread, this is the kind of compatibility that can never happen - we'd have to go and rewrite the earlier version of Corona to handle the new parameters and data structures of the new Corona, which would mean development time spent on rewriting old code, and that is not a wise investment of development time (plus where do we stop... we add 13's functions into 12 Update 2, and Update 1 as well, what about just 12, and what about 11, and what about.....) So there is nothing for the Corona team to "improve" here, it's the nature of software when it adds new features :) The only way to avoid this is to have a time machine, so that now we finished Corona 13 we can go back in time and code the same things into Corona 12 Update 2, Update 1, and so on ;)

It can be taken as read for any release of Corona that if you save a scene from Corona version X, it will no longer be loadable / renderable in Corona version X-1 (of course you can get into fine details, and say it will be loadable / renderable so long as it did not use any of the new features or anything where a parameter has changed, but it's just safest to assume it will not load or render).

Of course what we DO take care about and can do something about is making sure something created in Corona version X-1 will load and render identically in Corona X.