Chaos Corona Forum
Chaos Corona for 3ds Max => [Max] Feature Requests => [Max] Resolved Feature Requests => Topic started by: maru on 2014-11-08, 19:32:23
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In some cases like lots of reflective surfaces + intensive lights, fireflies appear and don't go away after many passes. A quick way to get rid of them is to use the rayswitch material, put the reflective material into direct visibility slot and put material's copy without reflectivity into GI slot. How about automatizing this process? Like a "no caustics" checkbox next to material's reflectivity. Or something like additional MSI for reflective materials? Quick example in attachment. Better example here (https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-xpf1/v/t1.0-9/1461814_724583307622896_5744691908998782418_n.jpg?oh=aebbf734751c727eb9bc81ce08d17d0f&oe=54E27E1F&__gda__=1424448478_7176d561b5b4fd25670a3de23d7f02d9) (picture by Tanakov).
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Could you attach this scene, maru? I have one thing in my mind that i'd like to test.
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Here it is, slightly modified. I noticed strange things are happening to these objects when they are reflected or refracted ad messed up a little with their settings but generally it's the same thing.
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Now this is getting a bit hardcore when you want to do this with a glass object with absorption.
+10 to hardcore if it's reflected/refracted in another object. :/
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yep
you cut all secondary reflections without reflection in GI slot
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Ok, actually it looks quite fine with:
-the material without reflectivity in GI slot
-the normal material in all the other slots
Sometimes interactive rendering acts strange when switching materials in rayswitchmtl and this was the cause of my problems. It looks ok in final rendering.
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You can try also decrease MSI to 10 for example. It helps too in same cases
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As far as I remember Keymaster once wrote that MSI does not affect caustics generated by materials with 1.0 glossiness. But I may be wrong.
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I think this is bug, at least i reported it some time ago: https://forum.corona-renderer.com/index.php/topic,5169.msg35149.html#msg35149
I attached two pictures. both are rendered with exactly the same settings. The only difference is that clean version is rendered with normal exposure from start to finish and second one is started with -20 EV and after few passes exposure was set back to default.
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As far as I remember Keymaster once wrote that MSI does not affect caustics generated by materials with 1.0 glossiness. But I may be wrong.
Of course. MSI 1 is bad. But MSI 10 may be a good solution in this case. In the past MSI 10 even was default
I think this is bug, at least i reported it some time ago: https://forum.corona-renderer.com/index.php/topic,5169.msg35149.html#msg35149
I attached two pictures. both are rendered with exactly the same settings. The only difference is that clean version is rendered with normal exposure from start to finish and second one is started with -20 EV and after few passes exposure was set back to default.
You mean if EV was changed during rendering then we get extra noise?
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Kind of. Also, i've found that extreme overexposure is harmful as well as underexposure:
feature=youtu.be
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I think this is bug, at least i reported it some time ago: https://forum.corona-renderer.com/index.php/topic,5169.msg35149.html#msg35149
I attached two pictures. both are rendered with exactly the same settings. The only difference is that clean version is rendered with normal exposure from start to finish and second one is started with -20 EV and after few passes exposure was set back to default.
I don't think this is a bug. Pardon my lack of technical knowledge but as far as I remember and understand, sampling is "optimized" based on initial exposure settings so changing it during rendering will always result in some quality loss. You should find the exposure you want and then hit render again.
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Good to know.
I always thought there was something fishy with changing the exposure.
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I don't think this is a bug. Pardon my lack of technical knowledge but as far as I remember and understand, sampling is "optimized" based on initial exposure settings so changing it during rendering will always result in some quality loss. You should find the exposure you want and then hit render again.
Where did you read this ? I thought progressive mode in Corona simply samples identically each pixel, since there is no adaptivity. The "initial" (what is that ? 0 ?) exposure thus wouldn't matter at all. It works the same way for Progressive mode in Vray, which would otherwise sample adaptively based on pixel's brightness in set exposure, but in Progressive, it just oversamples everything equally.
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the MSI value is relative to the initial exposure... so changing exposure by 20 stops after starting render will produce weird behavior
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Where did you read this ?
Here:
https://forum.corona-renderer.com/index.php/topic,608.msg4587.html#msg4587
the max sample intensity parameter is relative to the current color mapping, so starting render with different exposures will result in different max sample intensity, and in turn to different amount of bias in the picture. This is so that for example MSI 10 results in the same amount of bias in dim interior shot and in bright exterior one. But once you change exposure after the render has started, you cannot change the already rendered bias.
:)
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And here comes the test:
*MSI is intentionally changed to 1
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Ok that's bit different thing, but still wasn't aware of that. Will mind it next time as I often like others start and keep renders under-exposed for post-production reasons, but this could cause some heavy bias in highlights.
Just changed default MSI in Vray3 (from 20 to 100) in current animation project which is already sampling based on quite natural exposure and I was shocked how dramatically everything improved. But I guess that's just flawed integration of all these new features there..
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So what difference are you seeing directly? I guess I currently haven't gotten my head around what those MSI values really mean in terms of visual change. Default at 20 seems.. okay?! what do I know. But is 100 considered high? slower? what kind of change do you expect to see?
Cheers
Edit: randomly found this through google! thanks :)
https://forum.corona-renderer.com/index.php?topic=3708.0
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Just remember that MSI does not affect only caustics but also GI. It cuts off intensity of light being bounced off of objects. The conclusion coming from this thread is that it's not a good idea to hit F9 and then significantly change exposure value. It's best if you set your desired exposure value first, and then render image.
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this topic got derailed... but either way it wont be implemented - MSI needs to be relative to stay consistent, and I wont implement more oldschool light transport hacks