Author Topic: Yet another critical problem with bump mapping  (Read 4101 times)

2020-04-16, 12:55:34

sirio76

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Is this the expected behavior??
Specular highlight vary wildly depending on the size of the render/distance from camera, seems also related to MIP mapping. It happens on both preview and real scene.


2020-04-16, 13:36:14
Reply #1

maru

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I think this one would be the same in 3ds Max. It's just how things work.
Marcin Miodek | chaos-corona.com
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2020-04-16, 13:53:44
Reply #2

Nejc Kilar

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I think this one would be the same in 3ds Max. It's just how things work.

Em, its just how things work in Corona or in real life as well? :)

Thanks for reporting, sirio76!
Nejc Kilar | chaos-corona.com
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2020-04-16, 14:25:46
Reply #3

maru

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I think this one would be the same in 3ds Max. It's just how things work.

Em, its just how things work in Corona or in real life as well? :)


In Corona/Max/C4D/other, anywhere where there is texture filtering involved. But of course a dev's opinion would be more relevant here.
Marcin Miodek | chaos-corona.com
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2020-04-16, 14:27:18
Reply #4

sirio76

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It's just how things work.
Not in real life ;) I'm building all my shaders using physical samples of material inside a real calibrated setup and a 3D equivalent scene, also calibrated using correct exposure and light intensity. Results are mostly close to real life(below just a couple examples) but when I use a material with strong bump, results are inconsistent. Simply take several shots of a leather at different distance, the highlights is consistent no matter how you look at it, in Corona is just wrong and it's worrisome that you do not consider this a critical issue. It needs to be investigated and fixed. Sorry for the rant but I'm investing time and resources in Corona and I want things to work properly ;)
« Last Edit: 2020-04-16, 14:33:41 by sirio76 »

2020-04-16, 14:38:32
Reply #5

sirio76

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Also, it's not the same with Cinema materials, no matter if I use MIP or other sampling methods. I do not have Vray installed anymore but I'm pretty sure it doesn't have this problem neither and to be honest in over 20 years of work in CG using tons of other engine I do not remember this behavior.


« Last Edit: 2020-04-16, 15:05:30 by sirio76 »

2020-04-16, 19:09:52
Reply #6

sirio76

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@maru or any other developers, have you seen that?

2020-04-16, 19:49:14
Reply #7

Fluss

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Wouldn't bump to roughness solve those sampling issues?

2020-04-16, 23:06:20
Reply #8

sirio76

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Wouldn't bump to roughness solve those sampling issues?

I don't know about this feature, can you elaborate?

2020-04-17, 12:17:45
Reply #9

maru

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Here is a reply from our dev team:

Quote
This issue is present in all renderers which perform texture filtering / mip-mapping and it needs special handling - here is a paper from Pixar which explains this well: https://graphics.pixar.com/library/BumpRoughness/paper.pdf

We may, however, look into this - so stay tuned!

Also, please note: I am not a developer. :)
Marcin Miodek | chaos-corona.com
Chaos Corona Support Team Lead | contact us

2020-04-17, 13:20:14
Reply #10

sirio76

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Thank a lot for looking into this, I really appreciate your support:)

2020-04-17, 13:25:38
Reply #11

sirio76

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In the mean while I've founded a combination of maps/parameters that works fairly well, but it took me a lot of effort because of the filtering issue and close-up still look different:


« Last Edit: 2020-04-19, 09:55:58 by sirio76 »

2020-04-19, 11:24:27
Reply #12

Redeemer

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Posted in 'I need help' but I guess it is the same bug as Sirio pointed out:
https://forum.corona-renderer.com/index.php?topic=28892.0


2020-04-19, 12:09:30
Reply #13

Fluss

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Here is a reply from our dev team:

Quote
This issue is present in all renderers which perform texture filtering / mip-mapping and it needs special handling - here is a paper from Pixar which explains this well: https://graphics.pixar.com/library/BumpRoughness/paper.pdf

We may, however, look into this - so stay tuned!

Also, please note: I am not a developer. :)

Great, I'm so happy to hear that you're considering to solve this!

2020-04-20, 08:51:36
Reply #14

Nejc Kilar

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I'd just like to point out that this report could potentially be about the same bug that I'm seeing here - https://forum.corona-renderer.com/index.php?topic=28382.0 :)
Nejc Kilar | chaos-corona.com
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