export obj with material metallic will from 0 to 1 #60150

New Issue

Robert Zhang · 2019-01-04T12:35:18+01:00

Robert Zhang commented

2019-01-04 12:35:18 +01:00

System Information
Operating system:windows 10 lastest
Graphics card:gtx980ti

Blender Version
blender 2.80.39

export a object with material when metallic set 0, re-import this obj object, metallic will change to 1. but if set 0.01 or something number just not 0 when export and that not going to happened.

**System Information** Operating system:windows 10 lastest Graphics card:gtx980ti **Blender Version** blender 2.80.39 export a object with material when metallic set 0, re-import this obj object, metallic will change to 1. but if set 0.01 or something number just not 0 when export and that not going to happened.

Robert Zhang commented

2019-01-04 12:35:18 +01:00

Added subscriber: @zhanghua

Philipp Oeser commented

2019-01-04 12:39:55 +01:00

Added subscriber: @lichtwerk

Philipp Oeser self-assigned this 2019-01-04 12:39:55 +01:00

Philipp Oeser commented

2019-01-04 12:39:55 +01:00

Confirmed, checking...

Dalai Felinto commented

2019-01-04 12:57:29 +01:00

Added subscriber: @dfelinto

Dalai Felinto commented

2019-01-04 12:57:29 +01:00

Please attach a sample file, and please specify the hash of the Blender you used for testing (e.g., 4d8ed937f2)

Please attach a sample file, and please specify the hash of the Blender you used for testing (e.g., 4d8ed937f226f4cdfa6f62fde5306b14c217e9c5)

Robert Zhang commented

2019-01-04 13:14:50 +01:00

output-obj.obj

output-obj.mtl

export-this-cube-to-obj.blend

Hash is today. by the way this bug always have when 2.80 have export obj feature.

[output-obj.obj](https://archive.blender.org/developer/F6171478/output-obj.obj) [output-obj.mtl](https://archive.blender.org/developer/F6171477/output-obj.mtl) [export-this-cube-to-obj.blend](https://archive.blender.org/developer/F6171485/export-this-cube-to-obj.blend) Hash is today. by the way this bug always have when 2.80 have export obj feature.

Philipp Oeser commented

2019-01-04 13:33:55 +01:00

Added subscribers: @mont29, @brecht

Philipp Oeser commented

2019-01-04 13:33:55 +01:00

blender/blender-addons@f9c31589f6 made some changes here.
Since obj materials are "old school" and dont really support PBR we are abusing the ambient term for metallic

on export:

use_mirror = mat_wrap.metallic != 0.0                
if use_mirror:
    fw('Ka %.6f %.6f %.6f\n' % (mat_wrap.metallic, mat_wrap.metallic, mat_wrap.metallic))
else:
    fw('Ka %.6f %.6f %.6f\n' % (1.0, 1.0, 1.0))

on import:

if line_id == b'ka':
    refl = (float_func(line_split[1]) + float_func(line_split[2]) + float_func(line_split[3])) / 3.0
    context_mat_wrap.metallic = refl
    context_material_vars.add("metallic")

It kind of makes sense to have "old school" ambient when metallic is zero, on the other hand this causes described behavior on import.
Without digging real deep I see two solutions:

always dump metallic into ka (but we dont get ambient then when metallic is zero)
keep export as is, but check illum < 3 [indicates no Reflection] on import and set metallic to zero then [<< this one has my vote...]

P881: #60150 snippet



diff --git a/io_scene_obj/import_obj.py b/io_scene_obj/import_obj.py
index 3185e5c2..adad3d98 100644
--- a/io_scene_obj/import_obj.py
+++ b/io_scene_obj/import_obj.py
@@ -324,6 +324,8 @@ def create_materials(filepath, relpath,
                         illum = get_int(line_split[1])
 
                         # inline comments are from the spec, v4.2
+                        if illum < 3:
+                            context_mat_wrap.metallic = 0.0
                         if illum == 0:
                             # Color on and Ambient off
                             print("WARNING, Principled BSDF shader does not support illumination 0 mode "

@mont29, @brecht: what do you think?

blender/blender-addons@f9c31589f6 made some changes here. Since obj materials are "old school" and dont really support PBR we are abusing the `ambient` term for metallic on export: ``` use_mirror = mat_wrap.metallic != 0.0 if use_mirror: fw('Ka %.6f %.6f %.6f\n' % (mat_wrap.metallic, mat_wrap.metallic, mat_wrap.metallic)) else: fw('Ka %.6f %.6f %.6f\n' % (1.0, 1.0, 1.0)) ``` on import: ``` if line_id == b'ka': refl = (float_func(line_split[1]) + float_func(line_split[2]) + float_func(line_split[3])) / 3.0 context_mat_wrap.metallic = refl context_material_vars.add("metallic") ``` It kind of makes sense to have "old school" ambient when metallic is zero, on the other hand this causes described behavior on import. Without digging real deep I see two solutions: - **always** dump metallic into ka (but we dont get ambient then when metallic is zero) - keep export as is, but check `illum` < 3 [indicates no Reflection] on import and set metallic to zero then [<< this one has my vote...] [P881: #60150 snippet](https://archive.blender.org/developer/P881.txt) ``` diff --git a/io_scene_obj/import_obj.py b/io_scene_obj/import_obj.py index 3185e5c2..adad3d98 100644 --- a/io_scene_obj/import_obj.py +++ b/io_scene_obj/import_obj.py @@ -324,6 +324,8 @@ def create_materials(filepath, relpath, illum = get_int(line_split[1]) # inline comments are from the spec, v4.2 + if illum < 3: + context_mat_wrap.metallic = 0.0 if illum == 0: # Color on and Ambient off print("WARNING, Principled BSDF shader does not support illumination 0 mode " ``` @mont29, @brecht: what do you think?

Bastien Montagne commented

2019-01-04 13:47:52 +01:00

@lichtwerk Also think solution #2 is better, please add a comment to that line about meaning of illum < 3 though. ;)

And not sure this is the right place/way to do that, would rather add an else to if do_reflection: condition (line 259 currently)?

@lichtwerk Also think solution #2 is better, please add a comment to that line about meaning of `illum < 3` though. ;) And not sure this is the right place/way to do that, would rather add an `else` to `if do_reflection:` condition (line 259 currently)?

Philipp Oeser commented

2019-01-04 14:15:50 +01:00

@mont29: generally agree, but putting it in the 259 area will fail if you only have one material, see

Finalize previous mat, if any.

(that is a bit worrying actually, I guess some other stuff will fail as well if you only have one material...)

Regarding this report: would prefer to put it like in P881, move on and have a look at the "finalize-mat-not-doing-its-thing-with-only-one-material" later... OK?

@mont29: generally agree, but putting it in the 259 area will fail if you only have **one material**, see > # Finalize previous mat, if any. (that is a bit worrying actually, I guess some other stuff will fail as well if you only have one material...) Regarding this report: would prefer to put it like in [P881](https://archive.blender.org/developer/P881.txt), move on and have a look at the "finalize-mat-not-doing-its-thing-with-only-one-material" later... OK?

Bastien Montagne commented

2019-01-04 14:26:56 +01:00

@lichtwerk arg! you are right, finalize is not called for last material (not relevant how many mats there are)!!! That I will fix first, then we can put your fix in (new) finalize func, as it should be :)