Using 3d models (.obj) AND materials (.mtl) in an opengl application

karthiksrini · wrote on 15 Mar 2011, 11:13

Hi,

I have been trying to figure out how to use .obj format 3d models and the associated material files (.mtl) using opengl in a Qt app.
I have had enough examples on loading the obj model into the application which I am able to do. But I can't figure out how to use the mtl files.

Any suggestions or pointers on this would be really useful.

Thanks,
Karthik

ZapB · wrote on 15 Mar 2011, 11:21

I think that you will have to parse the MTL files yourself and translate them into suitable calls to glLightfv. I do not know of anything with Qt that will do this for you.

Have you checked out the "Qt3d":http://qt.gitorious.org/qt-labs/qt3d stuff in gitorious? This may have some classes that can help you. I certainly think that it provides helpers fo rthe .obj format.

karthiksrini · wrote on 16 Mar 2011, 16:28

[quote author="ZapB" date="1300188083"]I think that you will have to parse the MTL files yourself and translate them into suitable calls to glLightfv. I do not know of anything with Qt that will do this for you.

Have you checked out the "Qt3d":http://qt.gitorious.org/qt-labs/qt3d stuff in gitorious? This may have some classes that can help you. I certainly think that it provides helpers fo rthe .obj format.[/quote]

Thanks. I was just hoping that someone would've already done something like parsing the mtl files and could possibly help me with that. I will checkout Qt3d though and see what's in it.

laumaya · wrote on 16 Mar 2011, 18:58

Hi,
Two others possibilities :

you can use "GLC_lib":http://www.glc-lib.net to load and view your model
you review code of the class : "GLC_ObjMtlLoader":http://www.glc-lib.net/doc/class_g_l_c___obj_mtl_loader.html

@+

karthiksrini · wrote on 17 Mar 2011, 09:26

[quote author="laumaya" date="1300301897"]Hi,
Two others possibilities :

you can use "GLC_lib":http://www.glc-lib.net to load and view your model
you review code of the class : "GLC_ObjMtlLoader":http://www.glc-lib.net/doc/class_g_l_c___obj_mtl_loader.html

@+[/quote]

Thanks. That sounds interesting. Let me dig my teeth into that see how it tastes... :D
laumaya, is that project something you run all by yourself?

laumaya · wrote on 17 Mar 2011, 09:52

[quote author="karthiksrini" date="1300353964"]
laumaya, is that project something you run all by yourself?[/quote]

Yes.

karthiksrini · wrote on 22 Mar 2011, 09:03

Laumaya, I am trying to build glc_lib and the examples. The main glc library builds fine. But when I tried to build example09, I get a linker error. Any idea? I have the .pro file configured to find the include files and libs.

@release/glwidget.o:glwidget.cpp:(.text+0x18c): undefined reference to _imp___ZN20GLC_3DViewCollection11boundingBoxEv' release/glwidget.o:glwidget.cpp:(.text+0x600): undefined reference to _imp___ZN20GLC_3DViewCollection11boundingBoxEv'
release/glwidget.o:glwidget.cpp:(.text+0x7d4): undefined reference to _imp___ZN9GLC_3DRepaSERKS_' release/glwidget.o:glwidget.cpp:(.text+0x11fb): undefined reference to _imp___ZN20GLC_3DViewCollection11boundingBoxEv'@

laumaya · wrote on 22 Mar 2011, 09:38

It seems that you have not installed GLC_lib correctly.
Please, check the help page of GLC_lib : "http://www.glc-lib.net/help.php":http://www.glc-lib.net/help.php

karthiksrini · wrote on 22 Mar 2011, 09:57

ZapB, I tried Qt3d and the model viewer example directly loaded the obj file along with mtl files! Thanks!
I however had some difficulty loading the 3ds format of the same model though.

karthiksrini · wrote on 22 Mar 2011, 10:28

[quote author="laumaya" date="1300786694"]It seems that you have not installed GLC_lib correctly.
Please, check the help page of GLC_lib : "http://www.glc-lib.net/help.php":http://www.glc-lib.net/help.php
[/quote]

Thanks! I was using qt creator and I didn't realize that I had forgotten the make install.
Another quick question. Can I load animated models too using GLC_lib?

laumaya · wrote on 22 Mar 2011, 12:30

No, GLC_lib doesn't support animated model.

hurricane · wrote on 16 Aug 2011, 07:04

hi karthik,

i have just started learning Qt.I m getting problems in loading 3D textures from obj files.Can u please send me some examples showing how to load 3d textures from obj files...

Regards
hurr[i]cane

karthiksrini · wrote on 16 Aug 2011, 08:13

[quote author="hurricane" date="1313478252"]hi karthik,

i have just started learning Qt.I m getting problems in loading 3D textures from obj files.Can u please send me some examples showing how to load 3d textures from obj files...

Regards
hurr[i]cane [/quote]

You can use both Qt 3D and GLC_Lib as mentioned. Both these have examples. I was able to directly load them using the examples.

hurricane · wrote on 17 Aug 2011, 06:20

I want to load 3D models and textures for symbian 3 devices using Qt with openGL ES 1.1 . Can u provide some example for that...

Regards
hurr[i]cane

karthiksrini · wrote on 17 Aug 2011, 07:25

[quote author="hurricane" date="1313562019"]I want to load 3D models and textures for symbian 3 devices using Qt with openGL ES 1.1 . Can u provide some example for that...

Regards
hurr[i]cane[/quote]

Ah, for symbian... Then I guess you can't use GLC Lib. (laumaya?)
However I think you should be able to use Qt 3d. I haven't tried it on symbian. So I don't have exact pointers for you there.