Author Topic: Bump changes strength depending on pixel size of the object on screen  (Read 1064 times)

2021-10-06, 20:22:45

flame146

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Software: 3ds max 2021, 2022, Cinema 4D R20 with Corona 6
Corona version: latest 6 version, and 7 version

Hi all, I recently started using Corona for 3ds max, and I've come across this strange behavior, maybe this is normal?
Bump changes intensity depending on the size of the object or resolution.
In my scene I have a sphere, 1 light, and a black material with reflection on and glossy at 1.0.  + a bit of self-illumination texture to show the shape of the sphere

When I'm up close, dispersion of reflection is all over the place because of bump, but the more I zoom out it gets sharper and sharper, far out and it feels like there's no bump on the material at all, it's pure sharp reflection.
I've tested this with Max's Noise map, bump map in bitmap form, and normal map, but it's the same.
I've noticed this in Corona 6 and 7, and also noticed it in Corona for C4D. I've made a test in FStorm, V-Ray and Scanline, and there's no bump scaling/weakening due to object size on screen, dispersion of reflection on bump looks the same up close and far. Here are a few screenshot showing and comparing the effect in FStorm.
Vertical red line shows where the dispersion is visible in closeup, and that same line is marked on the same position on far version.

This is causing me a lot of trouble when I'm tweaking a material up close, and when I render a full resolution image, everything looks different.

I've attached my test scene in max 2022
Thank you for your answers

2021-10-07, 07:49:05
Reply #1

philipbonum

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Hi

I've experienced similar results when comparing corona to fstorm, and I can confirm that the bump in fstorm seems to be better.
Interestingly I've had better results when using a normal map instead of a standard black and white bump map in corona, so you could try that instead and see if it's better.

2021-10-07, 09:25:44
Reply #2

flame146

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I've had better results when using a normal map instead of a standard black and white bump map in corona, so you could try that instead and see if it's better.
Hey!
Unfortunately, as mentioned in my first post, I've tried all bumping methods with the same result, procedural noise, bitmap texture, normal map.
But what worries me is that bump feature is broken from what I see. Because for example bump strength changes when you even change resolution.

2021-10-07, 09:28:42
Reply #3

philipbonum

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Ah, my mistake!

Here's hoping there's some better answers from the devs. Been wanting better bump since I tried FStorm :)


2021-10-11, 13:31:59
Reply #4

GeorgeK

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I am afraid I was unable to reproduce these comparisons successfully, granted I wasn't able to test this on F-Storm just yet, but for Corona-Vray-Arnold-LuxCore bump fidelity pretty much returned the same, with material settings set at 1.5 IOR and 0.5 Roughness.  Would it be possible to share that exact example scene with us?
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2021-10-11, 15:33:29
Reply #5

flame146

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Hi George, I've attached the scene in my first post, look at the bottom of the attachments - sphere_scene.zip. Hope this helps!

2021-10-11, 15:49:33
Reply #6

pokoy

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I am afraid I was unable to reproduce these comparisons successfully, granted I wasn't able to test this on F-Storm just yet, but for Corona-Vray-Arnold-LuxCore bump fidelity pretty much returned the same, with material settings set at 1.5 IOR and 0.5 Roughness.  Would it be possible to share that exact example scene with us?
One situation where this becomes really visible is if you use a bump map on a glass surface - for example a tiled gradient like on old car headlights. I've ran into this a few times, bump becomes 'invisible' if the object is small or camera is farther away. Close to the camera bump works and anything behind the glass is nicely distorted, farther away it looks as if there is no bump at all and the glass surface is clean and even.

2021-10-12, 14:22:43
Reply #7

GeorgeK

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Thanks everyone, will be looking into it further.

(Report ID=CRMAX-827)
For solutions, troubleshooting, ticket requests please visit - [link]