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Index › Programming Questions & Help › Other Libraries › Obj importer materials issue.
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Obj importer materials issue. (Read 899 times)
wxs
Obj importer materials issue.
Jul 27th, 2007, 4:38pm  
Hello,

I'm using the saito.objloader library, and have come across a weird bug. The obj files I'm using are exported from Blender. The bug is thus: I'm using untextured materials, and for some reasons the objects show up completely black. If, however, I go into the .obj file and remove both the line where it imports the matlib and the line where it sets the material, then the material shows up.

I thought maybe it was just an issue with my sketch, but even on the downloaded sample from the web page there is the same issue of untextured materials appearing black.
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polymonkey
Re: Obj importer materials issue.
Reply #1 - Jul 27th, 2007, 10:53pm  
The objloader get's it material color (the fill part in processing) from the Ka line in the mtl file. They are float values between 0 and 1 (0 to 255 in processing color terms) If the map_Kd line is blank then it should default to not using a texture and just use the Ka line as a fill color value for the model. In version 013 a bunch of material options went in to disable the mtl material and use your own.

Saito is in the middle of updating the official site but I've got a mirror of the new material changes here http://www.polymonkey.com/2008/page.asp?obj_loader

Having said all that I haven't done any tests with obj/mtl info out of blender so if none of this helps I'd be happy to check it out if you can post a link to the problem files.
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MattD(polymonkey)
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wxs
Re: Obj importer materials issue.
Reply #2 - Jul 31st, 2007, 4:12pm  
Well I realized that my problem was that the colorMode had been switched to HSB in the sketch. I was trying to have a red material (255, 0, 0), but it was being interpreted as a colour with 0 brightness and saturation.

Textures stil don't work for me, however. My files are thus:
Code:

# Blender3D v244 OBJ File: truck.blend
# www.blender3d.org
mtllib truck.mtl
o Grid
v -2.461555 -1.004614 1.000000
v 2.187815 -1.004614 1.000000
v -1.791051 -0.230420 1.000000
v -2.461555 -0.230420 1.000000
v -1.016858 0.543773 1.000000
v -0.758793 0.543773 1.000000
v 2.187815 1.043494 1.000000
v -0.758793 1.043494 1.000000
v -1.265245 -1.004614 1.000000
v -0.965245 -0.704614 1.000000
v -0.665245 -1.004614 1.000000
v 0.634755 -1.004614 1.000000
v 0.934756 -0.704614 1.000000
v 1.234756 -1.004614 1.000000
v 1.234755 -1.004614 -1.000000
v 0.934755 -0.704614 -1.000000
v 0.634755 -1.004614 -1.000000
v -0.665245 -1.004614 -1.000000
v -0.965245 -0.704614 -1.000000
v -1.265245 -1.004614 -1.000000
v -0.758793 1.043494 -1.000000
v 2.187815 1.043494 -1.000000
v -0.758793 0.543773 -1.000000
v -1.016858 0.543773 -1.000000
v -2.461555 -0.230421 -1.000000
v -1.791051 -0.230421 -1.000000
v 2.187815 -1.004614 -1.000000
v -2.461555 -1.004614 -1.000000
s 1
usemtl Material
f 1 3 4
f 1 9 3
f 3 9 10
f 3 10 5
f 5 10 6
f 6 10 11
f 6 11 8
f 2 7 8
f 8 11 12
f 8 12 13
f 2 13 14
f 2 8 13
f 25 26 28
f 26 20 28
f 19 20 26
f 24 19 26
f 23 19 24
f 18 19 23
f 21 18 23
f 21 22 27
f 17 18 21
f 16 17 21
f 15 16 27
f 16 21 27
f 5 6 23
f 5 23 24
f 1 4 25
f 1 25 28


and

Code:

# Blender3D MTL File: truck.blend
# Material Count: 1
newmtl Material
Kd 0.60 0.60 0.60
Ka 0.6 0.60 0.60
Ks 0.9 0.9 0.9
Ns 0.0
map_Kd cloud1.png 
d 1 
illum 2
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polymonkey
Re: Obj importer materials issue.
Reply #3 - Aug 1st, 2007, 12:13am  
The mtl file looks fine. The problem is that the obj file has no texture information(UV coordinates). What you want to see is a line that starts with "vt". This refers to the UV position of the vertex. Once there is "vt" information then the "f" line will also change. At the moment it is "f int". This int tells the face to look at the numbered "v" line for position. Once "vt" infomation is there the "f" line will look like this "f int/int".

So if you're seeing the texture on the model in blender then maybe check the export settings. Is there an option in the blender obj export to "export UV's" that kind of thing?
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MattD(polymonkey)
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