Corona output map render artifacts

[Phasma]

we have some very dark HDRI's here that produced some artifacts in the rendering when the camera settings were set to counterreact to that. I thought that this had something to do with the hdris themselfs but i could now reproduce these artifacts by just offsetting the hdri power using the corona output map like in this example

http://recordit.co/fYkGixaTML

at the end it seems that it has nothing to do with the corona output map though. A very dim hdri (taken during the night) will produce artifacts even without a corona output in between.

http://recordit.co/PzpC7kfJnU

I thought that this was a corona1.7 rc problem/limitation but it is present in 1.7 released today AND also occurs in Corona 1.6.

it would be nice if this could be fixed soon (maybe as an SP update or so)

[pokoy]

Probably something else, but what format is the map used here? If it's EXR, please resave in PS as HDR and try again. Not saying it will help but the EXR loader can produce artifacts with certain compression options.

[Phasma]

thanks, but all are saved as hdr already :-)

[pokoy]

Ok, thanks.

Make sure to include a repro scene here, looks like this should get fixed!

[Phasma]

ok. i did that. I could even reproduce this problem only using the corona sky... (1508941959_testszene.max)

[Phasma]

any news here?

[maru]

I can reproduce it on the reported scene, but I am afraid that the developers will need to take a look at this to provide explanations.

I may be wrong, but it looks like it has something to do with the enviro sampler in devel/debug. If you change from NormalDependent to Precise, it seems to render correctly. So if you need to have something like this rendered without the artifacts, you can use this as a workaround. See: https://coronarenderer.freshdesk.com/support/solutions/articles/12000021288
Just don't touch anything else! ;)

[Phasma]

Hey! thank you very very much for this tip! I will try it asap and report here! Thank you so much!

[Phasma]

This works! does this come with disadvantages regarding rendertime/memory? otherwise this is perfect and thenk you again very much!

[maru]

I am not really sure what is the difference. I cannot guarantee it will not render slower.

[Phasma]

it seems that rendertimes are not increased (at least not dramatically) so i think its all fine. Also all the other modes render fine except for this normal direction thing.... so it would be nice to have a little explanation of what these values do change in detail

[maru]

Generally nothing in the devel/experimental tab should be touched, unless it is suggested as a solution to some issue, like in this case. ;)

[mostafazayed]

please ,who use corona v4 have a solution to the problem of (corona output map) not appearing in corona version 4 3ds max?

[TomG]

The Corona Output map was replaced by the CoronaToneMapControl (to control whether something is affected by VFB processing or not) and the CoronaColorCorrect (for the color correction features). See https://corona-renderer.com/blog/corona-renderer-2-for-3ds-max-released/