Author Topic: Reflections doubts  (Read 4022 times)

2023-03-24, 11:24:18

mascab

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Hi,
I can't solve this issue.
Is it normal, in your opinion, that reflections are so strong?
I attached two screens from a kitchen: in the first one, you can see the reflection of the wall burned, while wall it is not; in the second one, reflection of dishes is brighter than dishes himselves, with a strong spotlight that is not present on dishes.
How is it possible that reflections turn out far brighter than the reflected object?
Where is my error?
Thanks
Best regards,
Massimo

2023-03-24, 11:38:18
Reply #1

Beanzvision

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Seems to be normal. I'm guessing it depends on the viewing angle vs light direction, IOR of the receiving surface. Can you share the material settings? Or a test scene? 
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2023-03-24, 11:54:18
Reply #2

mascab

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Material it's a simple surface with glossiness .99 and ior 1.5
In my opinion it can be possible such a behaviour.
Even with a mirror, reflection can't be brighter than reflected object.

Now I'm rendering a still image. As soon as render ends, I'll try to prepare a simple scene to share.
Thanks

2023-03-24, 12:12:08
Reply #3

TomG

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Also, which version of Corona, and which version of C4D?
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2023-03-24, 12:20:10
Reply #4

mascab

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Corona 9 with cinema 2023

2023-03-24, 13:42:27
Reply #5

romullus

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Reflection can't be brighter than the actual object itself, that's right, but what part of the environment is reflected directly from the object and what is reflected as a secondary reflection, is not necessarily the same thing. Highlight from the sun, or other bright light source can be invisible on the object, because its curvature, but when that same object is reflected in another surface, the highlight may appear visible and it may look that the object became brighter. It's simply optics. Corona does not invent things and it is physically accurate, Corona materials are written with energy conservation in mind, so you can be assure that they don't break physics laws.
I'm not Corona Team member. Everything i say, is my personal opinion only.
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2023-03-24, 14:39:08
Reply #6

mascab

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Ok, that's clear now.
Thanks

2023-03-24, 14:55:01
Reply #7

mascab

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Another example.
Here I have a mirror with a brushed metallic frame.
I decided to use a light with low intensity to add a spotlight on the curve of the frame.
The light is visible in reflection and included only the mirror and not the wall covering, so the luminous part of covering is due only to mirror reflection
In my mind, the wall covering should reflect the dark mirror I saw in the image, instead I have that large amount of light that I can't see on the mirror itself.
If I turn off visible in reflection from light, everything seems to be normal.

2023-03-24, 15:08:39
Reply #8

pokoy

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I think you are struggling to understand the principles of how light is reflected and what exactly a mirror plane does vs what you as the observer (or the camera) sees. If you look at reflective surfaces in the real world around you you'll probably see many of these seemingly 'wrong' reflections happening.
« Last Edit: 2023-03-27, 11:18:42 by pokoy »

2023-03-24, 15:20:27
Reply #9

mascab

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You are absolutely right. :-D

I tried to simulate a similar situation in reality... glossy ipad reflecting black brushed bin...
I can't find out how the reflection in my render can be so luminous...

But ok,  stop struggling.
« Last Edit: 2023-03-24, 15:29:53 by mascab »

2023-03-24, 22:51:43
Reply #10

Stefan-L

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if you are using the new physical material make sure to lower your ior for most materials. ior 1.5 is ok for glass like things, but most "normal surfaces" have less reflection strength

as one cannot dim the reflection any more via the reflection color you need to make that via lowering the ior to get realistic reflections

2023-03-24, 23:04:17
Reply #11

mascab

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I agree about lowering the ior to get a lighter reflection.

But I still don't understand how it is possible than in a reflection very near to the object (for example the one with the dishes) I can find "information" that aren't present in the object itself.
It can't be possible that, in almost 10cm, there is a difference in light direction to achieve such a result.

I work in 3d since 2004 and I never had such a strange behaviour...


2023-03-25, 14:48:50
Reply #12

Pepelecrabb

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The angle of incidence of a light source is equal to the angle of reflectance which is always true,  the angle of the camera and the angle of the subject plane receiving light are independent and variable.
I always think of shooting billiards, bouncing a ball off of a bumper when setting up lights.

2023-03-26, 21:44:22
Reply #13

romullus

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But I still don't understand how it is possible than in a reflection very near to the object (for example the one with the dishes) I can find "information" that aren't present in the object itself.
It can't be possible that, in almost 10cm, there is a difference in light direction to achieve such a result.

Apparently it's very possible. Look at the attachment - the phone can't be any closer to the hand cream tube and yet reflection on its screen is so much brighter than on the tube itself... exactly like it is in your renders ;]
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2023-03-26, 23:24:29
Reply #14

davetwo

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Also see example from my kitchen.