Cycles: Normalmap does not bake with Alpha #48948

New Issue

Manfred · 2016-07-26T18:56:35+02:00

Manfred commented

2016-07-26 18:56:35 +02:00

System Information
OS: Windows 10 64bit
GPU: HD7870 (Pitcairn)

Blender Version
Broken: 2.77a abf6f08 (also 2.77)
Worked: 2.76b f337fea

Short description of error
Baked Normalmap in cycles has no alpha

Exact steps for others to reproduce the error

open attached .blend file
hit bake in the properties window
baked image in the UV/Image Editor has a complete white alpha channel
bakeNormal_cycles_noAlpha.blend

**System Information** OS: Windows 10 64bit GPU: HD7870 (Pitcairn) **Blender Version** Broken: 2.77a abf6f08 (also 2.77) Worked: 2.76b f337fea **Short description of error** Baked Normalmap in cycles has no alpha ![bake.png](https://archive.blender.org/developer/F328382/bake.png) **Exact steps for others to reproduce the error** 1) open attached .blend file 2) hit bake in the properties window 3) baked image in the UV/Image Editor has a complete white alpha channel [bakeNormal_cycles_noAlpha.blend](https://archive.blender.org/developer/F328384/bakeNormal_cycles_noAlpha.blend)

Manfred commented

2016-07-26 18:56:35 +02:00

Changed status to: 'Open'

Manfred commented

2016-07-26 18:56:35 +02:00

Added subscriber: @manfredp

Brecht Van Lommel commented

2016-07-27 02:05:14 +02:00

Added subscriber: @brecht

Brecht Van Lommel commented

2016-07-27 02:05:14 +02:00

I can confirm the behavior change, but why do you consider this a bug? Which applications make use of the normal map alpha channel? Do other baking applications also leave alpha zero outside the mesh?

Standard RGBA image textures must be interpolated with premultiplied alpha to get correct results, which would give you black pixels outside the mesh and lead to distorted normals when viewing the object from far away. For that reason setting alpha to 1 works better for the renderers I'm familiar with.

I can confirm the behavior change, but why do you consider this a bug? Which applications make use of the normal map alpha channel? Do other baking applications also leave alpha zero outside the mesh? Standard RGBA image textures must be interpolated with premultiplied alpha to get correct results, which would give you black pixels outside the mesh and lead to distorted normals when viewing the object from far away. For that reason setting alpha to 1 works better for the renderers I'm familiar with.

Manfred commented

2016-07-27 12:55:51 +02:00

I would use that in rare cases when I bake in different sessions and combine the results later in Photoshop.

3dsMax 2012 had that functionality/choice ... don't know about newer versions though.

As I said it is only for rare cases but I found the choice very useful and if I didn't need the alpha channel I could just disable it in the UV/Image Editor. I understand that for further rendering an alpha channel in the normalmap is not a desired option because it leads to unwanted artifacts.

I would use that in rare cases when I bake in different sessions and combine the results later in Photoshop. 3dsMax 2012 had that functionality/choice ... don't know about newer versions though. As I said it is only for rare cases but I found the choice very useful and if I didn't need the alpha channel I could just disable it in the UV/Image Editor. I understand that for further rendering an alpha channel in the normalmap is not a desired option because it leads to unwanted artifacts.

Brecht Van Lommel commented

2016-07-27 23:14:55 +02:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2016-07-27 23:14:55 +02:00

Brecht Van Lommel self-assigned this 2016-07-27 23:14:55 +02:00

Brecht Van Lommel commented

2016-07-27 23:14:55 +02:00

Ok, thanks, I think we'll keep the behavior as is then.

Manfred commented

2016-07-27 23:33:44 +02:00

Thanks for the clarification (I really thought this was a bug) and your time.

steve miller commented

2019-08-25 18:12:37 +02:00

Added subscriber: @winnertakesteve-1

steve miller commented

2019-08-25 18:12:37 +02:00

i personally do consider this missing functionality. there is a "clear image" toggle that still exists when bake type is set to "Normal". this toggle effectively does nothing because every pixel is overwritten.

the existence of a "clear image" option at all seems to recognize workflows where maps need to be baked in sections and then combined - particularly high to low poly normals, where you want to isolate pieces to minimize normal crosstalk on intersecting geometries.

i agree this isn't necessarily intended for a final normal map, but its a very useful intermediate tool. also wouldn't the black pixels outside the mesh be equally a concern for albedo colour, where this transparency in baking is supported?

i personally do consider this missing functionality. there is a "clear image" toggle that still exists when bake type is set to "Normal". this toggle effectively does nothing because every pixel is overwritten. the existence of a "clear image" option at all seems to recognize workflows where maps need to be baked in sections and then combined - particularly high to low poly normals, where you want to isolate pieces to minimize normal crosstalk on intersecting geometries. i agree this isn't necessarily intended for a final normal map, but its a very useful intermediate tool. also wouldn't the black pixels outside the mesh be equally a concern for albedo colour, where this transparency in baking is supported?

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

Cycles: Normalmap does not bake with Alpha #48948