[Bf-committers] Please add invert green channel option in Normal Map node

[metalliandy]

While the differences people are pointing out are indeed differences 
between engines, it's quite usual to refer to each standard for the 
green channel as DirectX or OpenGL (at least in games).

There is also a clear difference between how OpenGL and DirectX render 
the green channel in normal maps and it is down to where the origin for 
each APIs texture coordinates begin. In OpenGL 0,0 is at the bottom left 
whereas in DirectX it is at the top left.

These differences change the direction of the UV "V" direction to be up 
or down which accounts for the Y+ in OpenGL or Y- in DirectX. While it 
is absolutely true that you could use whatever you want in your engine 
it is most common to stick to the convention of the API you are using.

Unity/Blender/Modo/Knald/3dCoat/Maya/NDO/Marmoset use the Y+ OpenGL 
standard by default
UE4/Cryengine/Max use the Y- DirectX standard by default.

As bakers often support the use of a toggle/flip green so they are not 
locked to any specific API (and for sanity of the user :) ) I think 
there is a good case for having a flip green option for both baking and 
rendering within Cycles/BI simply because it's nice to preview the 
normal map before exporting to another engine.

Cheers,

-Andy


On 15/04/2017 22:17, Dahlia Trimble wrote:
> For what it's worth, OpenGL does not specify how normal maps function; they
> are entirely implemented in application code (usually in shaders). You're
> probably seeing a difference between Blender and Unity or Unreal, not
> OpenGL and DirectX.
>
> On Sat, Apr 15, 2017 at 1:50 PM, Adriano Oliveira <adriano.ufrb at gmail.com>
> wrote:
>
>> @Mike
>>
>> Cycles bake already has a toggle like this for export. We need this in
>> Normal Map node to deal with NM textures baked for DirectX.
>>
>> Game engines like Unity and Unreal have an "invert green (y) channel"
>> option in texture properties.
>>
>> In my workflow, for instance, I model and animate in Blander, texture in
>> Substance Painter and render in Unreal. In Painter I export Normal Map
>> textures to Unreal with DirectX standard (inverted green channel in
>> relation do OpenGL standard). If I need to see my model with this texture
>> in Blender, I have to create a node setup to invert G before feeding Normal
>> Map node.
>>
>>
>> *Adriano A. Oliveira*
>> Professor Adjunto do Curso de Cinema e Audiovisual
>> Universidade Federal do Recôncavo da Bahia (UFRB)
>> Centro de Artes Humanidades e Letras (CAHL)
>> Matrícula: 1673892
>> (71) 99181-0123 [VIVO] / (71) 99146-8523 [TIM]
>>
>> 2017-04-15 15:01 GMT-03:00 patrick boelens <p_boelens at msn.com>:
>>
>>> I actually just ran into a case where I wanted to compare the custom
>>> normals I set up in Blender to those inside another app, so there is a
>>> use-case for real-time toggling as well.
>>>
>>>
>>> No idea how prevalent it is and whether it's worth the effort though, but
>>> figured I'd chime in.
>>>
>>>
>>> Cheers,
>>>
>>> Patrick
>>>
>>> ________________________________
>>> Van: bf-committers-bounces at blender.org <bf-committers-bounces@
>> blender.org>
>>> namens Mike Erwin <significant.bit at gmail.com>
>>> Verzonden: zaterdag 15 april 2017 04:49:08
>>> Aan: bf-blender developers
>>> Onderwerp: Re: [Bf-committers] Please add invert green channel option in
>>> Normal Map node
>>>
>>> On Fri, Apr 14, 2017 at 10:47 AM, Adriano Oliveira <
>> adriano.ufrb at gmail.com
>>> wrote:
>>>
>>>> I just miss one little thing: An check box option to invert textures'
>>> green
>>>> chennels in the Normal Map node.
>>>>
>>>> This is very important because Blender follow the OpenGL norms for
>> Normal
>>>> Map, but other softwares that may be integrated within a pipeline (like
>>>> Unreal) uses DirectX norms.
>>>>
>>> Is this only needed during import & export, or something you would toggle
>>> during the Blender session?
>>>
>>> Mike Erwin
>>> musician, naturalist, pixel pusher, hacker extraordinaire
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