[Plugin] Import OBJ with Materials v2.1 20131118

TIG

The cross-threading of the faces' vertices into 'bowtie' triangles - which then probably mess up the UV-mapping - must be in the OBJ file itself [?].
The OBJ Importer simply uses the f n/n nn/nn/ nnn/nnn... values to form the faces and mapping ? Unfortunately unless you can reproduce the problem in a file with relatively few faces it'll be all but impossible to plough through the data to find the problem instances... [+460+ faces here?].
I was hoping that the OBJ had some -ve face indices that were causing the problem which recent versions might have solved... but NO!
In SUp export the ordering of a face's vertices shouldn't be a problem as they should always return ordered, and in the correct 'clockwise-ness' for the face's normal direct ?

Jim

The vertexes in the 'f' line are out of order for whatever reason.

Creates a "bow tie":

Sketchup.active_model.entities.add_face([0,0], [1,1], [1,0], [0,1])

thomthom

So it's the OBJ data that's invalid... but Max manage to deal with it somehow.

I'll compare against the raw output from SU and see if it's SU or PS that mangles the geometry.

thomthom

It's SU generating the odd vertex order. Here's the OBJ directly from SU:

SU Export

TIG

Could you PM me the original textured SKP - I have a new embryonic OBJ-Exporter that might NOT do this glitch ?

notareal

Here is a model that seems to fail http://www.fileden.com/files/2009/5/30/2461193//dragon_scene_OBJ.rar (From CGTalk Frosted Glass Challenge). Maybe it's a bit large... but simlab obj importer seems to handle it.

honoluludesktop

TIG, Wow, nice piece of code. Lots stuff I have to learn, like next, case, when, def file.run(par1, par2), etc. Makes the code look more compact and easy to read. Oh well, if I looked here before starting what I am working on, I may not have understood:-)

Some of the stuff that's driving me nuts when writing importers, is that different exporters do not format the data exactly. SU's DxfIn treats "10", and " 10" equally, and many exporters ignore the convention that is " 10". I don't know if I should go back and fix my code to read "10" or not. It's no problem for my use, and would like to "share", but am concerned about posting something that may not work for some.

TIG

honoluludesktop
A DXF has alternating lines for 'code' and 'value'.
So if it's an odd-numbered line then it's always 'code' and if it's an even-numbered line it's always the previous line's code's 'value'...
It's a DXF convention to indent the 'code' number, BUT it's not necessary and any importer should strip off leading spaces anyway...

  0
SECTION
  2
HEADER
  9
etc

is the same as

0
SECTION
2
HEADER
9
etc

To see a DXF 'parser' look at my DXF Text Importer http://forums.sketchucation.com/viewtopic.php?p=194488#p194488

honoluludesktop

OK, thanks, I will look at it. I may have to wait for a complete rewrite to parse the 'code'. Isn't some of that done in the Obj translator? I couldn't tell since I am not at all familiar with Obj.

When I think about it, any translator can be a modular app., just as you did with the text importer as a supplement to SUs DxfIn. My own interest has been limited to very basic geometry, and dealing with the anomalies of my Cad's DxfIn/Out. It suits me since I use SU exclusively for visualization and modeling, and Cad for functional diagramming and production drawings. Accordingly, I only require the basic geometry to pass between SU and Cad.

onesimo

hi tig! thanks for the importer. its working perfectly for me on my archmodels.
i should have tried it when i first saw the post. thanks so much and i really appreciate your work.

onesimo

hi tig! im using 3ds max design 2011. when i open/obj import my exported file the textures are not showing.. it seems my .mtl file is different from the one posted (the one with the building). thanks!

my exported file from 3ds max

Krisidious

I imported an Obj file and the uvw map came in perfectly.

but some geometry was lost... any ideas on why?

TIG

@onesimo said:

hi tig! im using 3ds max design 2011. when i open/obj import my exported file the textures are not showing.. it seems my .mtl file is different from the one posted (the one with the building). thanks!

The MTL file has the lines

Ka 0.0000 0.0000 0.0000
Kd 0.0000 0.0000 0.0000
Ks 0.3500 0.3500 0.3500

they should read

Ka 0.0000 0.0000 0.0000
Kd 0.3500 0.3500 0.3500
Ks 0.0000 0.0000 0.0000

The Kd value sets the material's RGB color in the original MTL file it is [0,0,0] = 'black'
If you swap the Kd and Ks values and it renders 'gray' as expected...
Only the 'Kd' value is read by the SUp importer - the other twp 'K' values involve reflectivity and spectral info that SUp can't use and are superfluous...
Also if an MTL material has an image_file defined at the end of its text_block that will be used as its 'texture', overriding any RGB 'color' - but this material does not have a texture.
When you make an OBJ file check that its MTL file's 'Kd' is set to RGB otherwise it will be 'black'.

TIG

@krisidious said:

I imported an Obj file and the uvw map came in perfectly.
but some geometry was lost... any ideas on why?

The OBJ importer should import all available geometry described in the file - sometimes with very convoluted meshes it can fail, but it rarely 'misses' stuff out - in fact it's more likely to try and tie vertices together that don't join in the original with extra geometry!
If you import the same file into another app - like Blender? - is it still missing parts?
If so perhaps the export didn't pick up parts in the first place
What app made the OBJ file originally?

Krisidious

@tig said:

@krisidious said:

I imported an Obj file and the uvw map came in perfectly.
but some geometry was lost... any ideas on why?

The OBJ importer should import all available geometry described in the file - sometimes with very convoluted meshes it can fail, but it rarely 'misses' stuff out - in fact it's more likely to try and tie vertices together that don't join in the original with extra geometry!
If you import the same file into another app - like Blender? - is it still missing parts?
If so perhaps the export didn't pick up parts in the first place
What app made the OBJ file originally?

it came from AC3D, I tried the file in 3Dmax and it's all there. it's no biggy, I don't need to do it. I was just trying it out.

TIG

Kristoff

Can you PM me the OBJ/MTL etc [zipped].
I'd like to see if I can find out the cause anyway...

TIG

Kristoff

I got the 'Ford' OBJ file by PM.
It imported fine for me... IF I set the units to 'meters' - it also then comes in at the correct 'size'!
If you use 'mm' it is tries to make some edges that are 1000 times too small 0 as you might have seen in other threads that guarantees that geometry fails to be made. SUp / OpenGL doesn't like anything smaller than about 0.1mm...
The importer reads the OBJ file's 'header' and if it has 'units=' in it then that is given as the default displayed in the dialog as it starts, otherwise it defaults to 'inches'.
In the case of this 'Ford' OBJ there's no header info at all, so you need to take a guess - trying larger scale units should always make geometry as the 0.1mm is never likely but of course the imported object might then be the wrong 'size'.
Meters are a common unit in non-US made OBJs...
So, panic over - try it in 'meters' and it should work fine...

Krisidious

damn counting with 10's burned me again... (hits self in head meter not millimeter!)

awesome plugin. I also love the groupstoobj.rb ...

eloiraiol

Because the images do not appear in the trial, only show the textures in SketchUp itself. Where is a picture is blank!

TIG

@eloiraiol said:

Because the images do not appear in the trial, only show the textures in SketchUp itself. Where is a picture is blank!

Please explain your problem another way... I don't understand