Incorrect reflections in fresnel node with flipped normals. #46115

New Issue

stanislav · 2015-09-14T22:12:38+02:00

stanislav commented

2015-09-14 22:12:38 +02:00

Windows 7 x64 SP1
Core i5 2500
Quadro 600
Blender 2.75a

CPU render
Model imported from Rhinoceros 3d with FBX (same trouble with OBJ files).
I want to do the car paint shader with Fresnel node.
Blender objects have good reflections (see helmets).

Windows 7 x64 SP1 Core i5 2500 Quadro 600 Blender 2.75a CPU render Model imported from Rhinoceros 3d with FBX (same trouble with OBJ files). I want to do the car paint shader with Fresnel node. Blender objects have good reflections (see helmets). ![2015-09-14 22 56 36.png](https://archive.blender.org/developer/F233320/2015-09-14_22_56_36.png)

stanislav commented

2015-09-14 22:12:38 +02:00

Changed status to: 'Open'

stanislav commented

2015-09-14 22:12:38 +02:00

Added subscriber: @stanislavmarchevsky

Marco G commented

2015-09-14 22:33:09 +02:00

Added subscriber: @marcog

Marco G commented

2015-09-14 22:33:09 +02:00

Check normals. Most likely they are inverted

stanislav commented

2015-09-14 22:41:14 +02:00

reflections are not the same in both normal directions?

Bastien Montagne commented

2015-09-14 22:54:57 +02:00

Added subscriber: @mont29

Bastien Montagne commented

2015-09-14 22:54:57 +02:00

Please follow our submission template and guidelines and make a complete, valid bug report, with required info, precise description of the issue, precise steps to reproduce it, small and simple .blend and/or other files to do so if needed, etc.

Please follow our submission template and guidelines and make a complete, valid bug report, with required info, precise description of the issue, precise steps to reproduce it, **small and simple** .blend and/or other files to do so if needed, etc.

stanislav commented

2015-09-14 23:45:53 +02:00

I want to use Blender in rendering for industrial design objects. Before I used Maxwell.

I have some inconvenience:

Why reflection in fresnel node are not the same in both normal directions? It`s physically based render.
Why, flipping normals, Blender recalculate them? You can see, good normals and bad recalculated by Blender. Screenshot:

Blend file is here tires-normal.blend

Thanks.

I want to use Blender in rendering for industrial design objects. Before I used Maxwell. I have some inconvenience: 1. Why reflection in fresnel node are not the same in both normal directions? It`s physically based render. 2. Why, flipping normals, Blender recalculate them? You can see, good normals and bad recalculated by Blender. Screenshot: ![2015-09-15 00 35 08.png](https://archive.blender.org/developer/F233328/2015-09-15_00_35_08.png) Blend file is here [tires-normal.blend](https://archive.blender.org/developer/F233327/tires-normal.blend) Thanks.

Aaron Carlisle commented

2015-09-15 03:28:00 +02:00

Added subscriber: @Blendify

Bastien Montagne commented

2015-09-15 09:50:36 +02:00

Well… Main issue here is, why does your model comes with flipped normals?

That said, 'filp normals' tool does not yet support custom normals (it merely reverse the winding of faces and recompute face and vertex normals). This is more a TODO than a bug really, but it should not be that hard to implement, will give it a try.

Well… Main issue here is, why does your model comes with flipped normals? That said, 'filp normals' tool does not yet support custom normals (it merely reverse the winding of faces and recompute face and vertex normals). This is more a TODO than a bug really, but it should not be that hard to implement, will give it a try.

Bastien Montagne self-assigned this 2015-09-15 09:51:09 +02:00

stanislav commented

2015-09-15 10:10:07 +02:00

Thanks :)

I know, how to flip normals in Rhinoceros. But you import the model, then transform it, and than you see, that normals are flipped... :(

Importing models in other renders, as Octane, Arion, Maxwell, Indigo there is no trouble, because reflections are the same in both directions. When I use fresnel reflection in Blender - there is differrence in reflecvtion function, and it depends on normal direction.

Thanks :) I know, how to flip normals in Rhinoceros. But you import the model, then transform it, and than you see, that normals are flipped... :( Importing models in other renders, as Octane, Arion, Maxwell, Indigo there is no trouble, because reflections are the same in both directions. When I use fresnel reflection in Blender - there is differrence in reflecvtion function, and it depends on normal direction.

Bastien Montagne commented

2015-09-15 10:17:01 +02:00

Added subscriber: @Sergey

Bastien Montagne commented

2015-09-15 10:17:01 +02:00

Well, I do not have knowledge here to judge Fresnell reflection behavior, we should summon @Sergey here for that. ;)

As for flipping custom normals, in fact current Blender op operates in Edit mode, where clnors are not handled. Will try to make a temp solution with a py script for now, supporting some custom normal editing in Edit mode is really a TODO currently.

Well, I do not have knowledge here to judge Fresnell reflection behavior, we should summon @Sergey here for that. ;) As for flipping custom normals, in fact current Blender op operates in Edit mode, where clnors are not handled. Will try to make a temp solution with a py script for now, supporting some custom normal editing in Edit mode is really a TODO currently.

Bastien Montagne changed title from ~~Incorrect reflections in fresnel node.~~ to Incorrect reflections in fresnel node with flipped normals.

2015-09-15 11:57:27 +02:00

Bastien Montagne removed their assignment 2015-09-15 11:57:27 +02:00

Sergey Sharybin was assigned by Bastien Montagne

2015-09-15 11:57:27 +02:00

Bastien Montagne commented

2015-09-15 11:58:55 +02:00

Added a new addon (custom normals tools), which contains an operator to flip custom mesh normals, cannot do more for now. Reassigning the task to Sergey, since the Fresnel with flipped normals is its area. ;)

Sergey Sharybin commented

2015-09-16 15:17:52 +02:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2015-09-16 15:17:52 +02:00

Sergey Sharybin commented

2015-09-16 15:17:52 +02:00

Fresnel term will depend on whether ray enters or leaves the medium and Cycles uses normal direction to check this. That being said you can't really expect render result of original tire and tire after flipping normals to be the same.

So thanks for the report, but it seems to behave exactly as it's expected currently.

Fresnel term will depend on whether ray enters or leaves the medium and Cycles uses normal direction to check this. That being said you can't really expect render result of original tire and tire after flipping normals to be the same. So thanks for the report, but it seems to behave exactly as it's expected currently.

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Incorrect reflections in fresnel node with flipped normals. #46115