Object File Text Format (*.obj) - GameCreators Forum

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Sph!nx

15

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Joined: 3rd Dec 2008

Location: The Netherlands

Posted: 2nd Jul 2016 22:13

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Hey everybody!

Been a little while. How y'all doing?

I've been fiddling around with .obj files and discovered when opened in notepad, it is not encrypted, this I could use this for useful things. Now it's readable, not completely understandable for me yet. I've tried googling on the subject but could not find a straight to the point explanation that I could understand.

What I wish to achieve? Create simple meshes in notepad (to create cube/tile based maps) with the use of an atlas texture.

It's for a retro fps dungeon crawler/shooter game! Later on I will create an editor for the engine, but first I need to understand this part.

Anyone has some resources/info on the subject? Any help is greatly appreciated. Thanks!!

Regards Sph!nx

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Sph!nx

15

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Joined: 3rd Dec 2008

Location: The Netherlands

Posted: 3rd Jul 2016 17:26 Edited at: 3rd Jul 2016 18:24

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Hey, I've made some progress. Managed to create a square of two faces, facing upwards (for use as a floor tile) (size 64x64). I currently use a single image (not atlas) and wish to UV map the image on the square, but I do not know how to get the UV coordinates from the vertexes and how to implement it. I know it is part of the "vt" lines.

Here is the "test.obj" file I'm working with:

+ Code Snippet

# Floor Plane Vertexes
v 0.000000 0.000000 0.000000
v 0.000000 0.000000 64.000000
v 64.000000 0.000000 0.000000
v 64.000000 0.000000 64.000000
# Smootshading: 1/off
s off

# UV Coordinates (HALP!!)
vt 0.000000 0.000000 0.000000

# Floor Plane Faces
f 1 2 3
f 4 3 2

Any help is much appreciated! Thanks

EDIT
I've figured it out! I've added comments which should explain it. Here are my findings:

+ Code Snippet

# Floor Plane Vertexes (A)
v 0.000000 0.000000 0.000000
v 0.000000 0.000000 64.000000
v 64.000000 0.000000 0.000000
v 64.000000 0.000000 64.000000

# UV Coordinates. "0.0 0.0" is top left. "1.0 1.0" is bottom right of image (B)
vt 0.000000 1.000000
vt 0.000000 0.000000
vt 1.000000 1.000000
vt 1.000000 0.000000

# Smootshading: 1/off (All faces created after this will use this command)
s off
# Floor Plane Faces (A/B)
f 1/1 2/2 3/3
f 4/4 3/3 2/2

Regards Sph!nx

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Blendman

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Joined: 17th Feb 2014

Location: Arkeos

Posted: 4th Jul 2016 07:43

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HI

I'm interested about this format too (and other format like b3D for example).
Here is an example of a cube made in blender and exported in .obj :

+ Code Snippet

# Blender v2.76 (sub 0) OBJ File: ''
# www.blender.org
mtllib cube.mtl
o Cube
v 1.000000 0.000587 -1.000000
v 1.000000 0.000587 1.000000
v -1.000000 0.000587 1.000000
v -1.000000 0.000587 -1.000000
v 1.000000 2.000587 -0.999999
v 0.999999 2.000587 1.000001
v -1.000000 2.000587 1.000000
v -1.000000 2.000587 -1.000000
vn 0.000000 -1.000000 -0.000000
vn 0.000000 1.000000 0.000000
vn 1.000000 0.000000 0.000000
vn -0.000000 -0.000000 1.000000
vn -1.000000 -0.000000 -0.000000
vn 0.000000 0.000000 -1.000000
usemtl Material
s off
f 1//1 2//1 3//1 4//1
f 5//2 8//2 7//2 6//2
f 1//3 5//3 6//3 2//3
f 2//4 6//4 7//4 3//4
f 3//5 7//5 8//5 4//5
f 5//6 1//6 4//6 8//6

And the material :

+ Code Snippet

# Blender MTL File: 'None'
# Material Count: 1

newmtl Material
Ns 96.078431
Ka 1.000000 1.000000 1.000000
Kd 0.640000 0.640000 0.640000
Ks 0.500000 0.500000 0.500000
Ke 0.000000 0.000000 0.000000
Ni 1.000000
d 1.000000
illum 2

Informations about .obj format here (I think it's interesting for you

) :
http://www.hodge.net.au/sam/blog/wp-content/uploads/obj_format.txt
http://paulbourke.net/dataformats/obj/
http://www.fileformat.info/format/wavefrontobj/egff.htm

https://en.wikipedia.org/wiki/Wavefront_.obj_file

I think you should find some informations about .obj in the blender documentation :
https://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Import-Export/Wavefront_OBJ

I hope this will help you (and continue to post your example

)

AGK2 tier1 - http://www.dracaena-studio.com

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Sph!nx

15

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Joined: 3rd Dec 2008

Location: The Netherlands

Posted: 4th Jul 2016 13:11

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Thank you very much, Blendman! Much appreciated.

On the subject of materials... Correct me if I'm wrong. AppGameKit does not use the material data (besides the UV mapping). AppGameKit can only use one material (assigned through AppGameKit code) on each object. This is what I've learned so far... correct?

Thanks again!

Regards Sph!nx

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Mobiius

Valued Member

21

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Joined: 27th Feb 2003

Location: The Cold North

Posted: 4th Jul 2016 13:12 Edited at: 4th Jul 2016 13:13

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Quote: "GK can only use one material (assigned through AppGameKit code) on each object. "

As loaded in the object, yes.

But you can multi texture for shaders.

Now Visit My Website

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MikeMax

AGK Academic Backer

12

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Joined: 13th Dec 2011

Location: Paris

Posted: 4th Jul 2016 21:06 Edited at: 4th Jul 2016 21:23

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I have coded 3 years ago an OBJ Loader which parse OBJ and MTL file to support multiple meshes ans multiple textures. Its was used by My AppGameKit SpeedRacer game :

I have also coded a B3D Loader which reads Binary data and recreates OBJ meshes with textures and also support lightmaps (B3D + Lightmaps exported with 3D World Studio, DeleD CE for example) with a cache system which preserves previous generated OBJ Files. I plan to adapt it with the new Memblock commands (AGK2) to create meshes with faster loading but i have actually no time for that.

Interested ? (i have to clean the code before... and the code may not be fully optimized!)

--------------------------------
Join us on dedicated AppGameKit WeeKChat :

https://week.chat/room/AppGameKit

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SoftMotion3D

AGK Developer

19

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Joined: 24th Aug 2005

Location: Calgary,Alberta

Posted: 5th Jul 2016 00:02

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ah yes... the obj format. I actually build obj files within agk code to load in 3d models. Its a very easy format to write and agk is fairly fast at coding the obj file.... saving ... and loading back in to use. My current game engine does this and makes it possible to have limited to no 3d media since its capable of creating the meshes with code.

If you got any more questions about obj... i could probably help.

as you figured out "v " is for vertex data. " vn " for normals data "vt" for uv data and "f " for index data that links the vertex and normals and texture data to form a triangle or quad.
let me know if you need anymore help with this.

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blink0k

Moderator

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Joined: 22nd Feb 2013

Location: the land of oz

Posted: 5th Jul 2016 03:09

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MikeMax. I would luv to see that code! Awesome stuff

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Sph!nx

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Joined: 3rd Dec 2008

Location: The Netherlands

Posted: 7th Jul 2016 16:31

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Hey guys, thanks for all the replies! I'm still learning and experimenting stuff.

@ MikeMax, that looks awesome and would love to take a peek!

@ SMD, I know you are very much experienced with this stuff. I've seen you do cool stuff with your voxel techniques. Very impressive stuff. If I have questions I'll be sure to ask!

Regards Sph!nx

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AppGameKit Classic Chat / Object File Text Format (*.obj)