[osg-users] Newbie Texture Question

[Robbo]

Hi,

I am trying to learn OSG for use in Flightgear.  I have seen a technique
used regularly that I am not able to figure out.

Essentially a scene is using an rgb file which is transparent and whilst
quite large (1024x768), contains many different 'icons' of smaller size and
what appears to be an 'alpha mask' for the main image area.  These icons
appear to be extracted and used within a dynamic scene, but I am not sure
how this is done as it does not appear obvious in the code (i was expecting
some image coordinates at least).

The particular example within Flightgear (for those who may be familiar) is
wxradar.cxx and wxecho.rgb)

Could somebody please take the time to explain how This works in principle
and what the technique is called?

Many thanks,

Robbo
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Re: [osg-users] Newbie Texture Question

[Chris 'Xenon' Hanson]

On 10/9/2011 9:28 AM, Robbo wrote:
 I am trying to learn OSG for use in Flightgear.  I have seen a technique used 
 regularly
 that I am not able to figure out.
 Essentially a scene is using an rgb file which is transparent and whilst 
 quite large
 (1024x768), contains many different 'icons' of smaller size and what appears 
 to be an
 'alpha mask' for the main image area.  These icons appear to be extracted and 
 used within
 a dynamic scene, but I am not sure how this is done as it does not appear 
 obvious in the
 code (i was expecting some image coordinates at least).
 The particular example within Flightgear (for those who may be familiar) is 
 wxradar.cxx
 and wxecho.rgb)
 Could somebody please take the time to explain how this works in principle 
 and what the
 technique is called?

  Sounds a bit like a Texture Atlas.

  Yes, I would expect either the UV coordinates to be altered, or perhaps the
transform/translate of the texture coordinate matrix.

 Robbo


-- 
Chris 'Xenon' Hanson, omo sanza lettere. xe...@alphapixel.com 
http://www.alphapixel.com/
  Digital Imaging. OpenGL. Scene Graphs. GIS. GPS. Training. Consulting. 
Contracting.
There is no Truth. There is only Perception. To Perceive is to Exist. - 
Xen
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Re: [osg-users] newbie texture question

[Alberto Luaces]

David Cofer writes:

 I added the recommended line to the mtl file and it did apply the texture to 
 the object this time, but it was still incorrect compared to what is seen in 
 directx. See picture. I tried a couple of the options for the map_Kd command 
 and none helped. 

I think the difference lies in the coordinate system for the texture
space. If you flip your bmp upside down, you will get the correct
result. I don't know if it's a Directx or bmp thing. Try to convert your
file to other format, e.g. jpg to see if it still happens.

 Also, this will not help me in the long run becuase my final application has 
 the option of allowing the user to specify the image file they want to use as 
 a texture for their objects. This means I will need to re-apply the texture 
 at runtime, and not load it in from the mtl file. I believe that requires the 
 use of the stateset objects, which are not working correclty for me. 

I suspect that the obj plugin *might* be discarding the uv info if it
not finds any texture image in the material definition. You can check
the source of the obj plugin to be sure.

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Re: [osg-users] newbie texture question

[David Cofer]

You rock Alberto!! I flipped the bmp and it mapped correctly. It would never 
have occured to me to do that in a million years on my own. Thanks.

I tried to step into the osg code, but it did not work. It just stepped over 
it. I am loading the debug versions, so I am not completly sure why it is not 
working. I will keep playing with it to see if it is dropping the u,v coords as 
you suspect. Worst case scenario I just remove the ability to apply a texture 
at run-time for a mesh and make them specify it in the mesh file. 

Thanks for your help.
David

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Re: [osg-users] newbie texture question

[Jean-Sébastien Guay]

Hi David,


I will keep playing with it to see if it is dropping the u,v coords as you 
suspect. Worst case scenario I just remove the ability to apply a texture at 
run-time for a mesh and make them specify it in the mesh file.


Or, just map a dummy white 1x1 texture by default, so that the obj 
loader thinks there's a texture and keeps the UVs (if that's indeed the 
problem).


Applying a texture at run time is not a problem, it's getting the model 
loaded with the proper texture coordinates that is... After that it's 
just a matter of


  model-getOrCreateStateSet()-setTextureAttributeAndModes(0,
  my_new_texture.get(), osg::StateAttribute::ON);

J-S
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Re: [osg-users] newbie texture question

[Alberto Luaces]

David Cofer writes:

 You rock Alberto!! I flipped the bmp and it mapped correctly. It would never 
 have occured to me to do that in a million years on my own. Thanks.

Glad I could help :) See below.

 I tried to step into the osg code, but it did not work. It just stepped over 
 it. I am loading the debug versions, so I am not completly sure why it is not 
 working. I will keep playing with it to see if it is dropping the u,v coords 
 as you suspect. Worst case scenario I just remove the ability to apply a 
 texture at run-time for a mesh and make them specify it in the mesh file. 

Meanwhile you could specify some default texture of yours in the file
and then use the osgUtil::Optimizer::TextureVisitor class to change it
for another at run-time.

--
Alberto
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Re: [osg-users] newbie texture question

[Jason Daly]

David Cofer wrote:

You rock Alberto!! I flipped the bmp and it mapped correctly. It would never 
have occured to me to do that in a million years on my own. Thanks.
  


Random facts you may or may not care about...

DirectX uses a different origin from OpenGL when applying textures 
(DirectX uses the top-left, while OpenGL uses the bottom-left).


You might also run into problems with winding order of primitives 
(triangles, etc.).  Unlike the rest of the world, DirectX uses 
right-handed coordinates.  This results in vertices for primitives being 
specified in a clockwise order, unlike OpenGL which expects 
counter-clockwise vertices.


You're probably OK since you're using a .obj file directly.  When I was 
writing the Half-Life 2 loader, I had to flip the vertex order as I was 
loading them, or I would get back-faces facing out, which would 
disappear when back-face culling was turned on.


--J

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Re: [osg-users] newbie texture question

[David Cofer]

Ok. I can get the mesh to work using the mtl file, but I have gone back and 
tried to get the basic geometric textures working and I am still having 
problems. I created a simple geometry for a box using the code shown below. I 
set it up to try and place the texture file once on each face. When I run this 
I get something that looks exactly like what happens when I just use the box 
shape. This is getting frustrating. Any help with what I am doing wrong would 
be greatly appreciated.


Code:

osg::Geometry* CreateBoxGeometry()
{
 osg::Geometry* box = new osg::Geometry;

 // Vertices
 osg::Vec3Array* vertices = new osg::Vec3Array;
 vertices-push_back(osg::Vec3(-.5, -.5, -.5)); // 0
 vertices-push_back(osg::Vec3( .5, -.5, -.5)); // 3
 vertices-push_back(osg::Vec3( .5, -.5,  .5)); // 5
 vertices-push_back(osg::Vec3(-.5, -.5,  .5)); // 1

 vertices-push_back(osg::Vec3(-.5, -.5,  .5)); // 1
 vertices-push_back(osg::Vec3( .5, -.5,  .5)); // 5
 vertices-push_back(osg::Vec3( .5,  .5,  .5)); // 7
 vertices-push_back(osg::Vec3(-.5,  .5,  .5)); // 4

 vertices-push_back(osg::Vec3(-.5, -.5, -.5)); // 0
 vertices-push_back(osg::Vec3(-.5, -.5,  .5)); // 1
 vertices-push_back(osg::Vec3(-.5,  .5,  .5)); // 4
 vertices-push_back(osg::Vec3(-.5,  .5, -.5)); // 2

 vertices-push_back(osg::Vec3( .5, -.5, -.5)); // 3
 vertices-push_back(osg::Vec3( .5,  .5, -.5)); // 6
 vertices-push_back(osg::Vec3( .5,  .5,  .5)); // 7
 vertices-push_back(osg::Vec3( .5, -.5,  .5)); // 5

 vertices-push_back(osg::Vec3( .5,  .5, -.5)); // 6
 vertices-push_back(osg::Vec3(-.5,  .5, -.5)); // 2
 vertices-push_back(osg::Vec3(-.5,  .5,  .5)); // 4
 vertices-push_back(osg::Vec3( .5,  .5,  .5)); // 7

 vertices-push_back(osg::Vec3( .5, -.5, -.5)); // 3
 vertices-push_back(osg::Vec3(-.5, -.5, -.5)); // 0
 vertices-push_back(osg::Vec3(-.5,  .5, -.5)); // 2
 vertices-push_back(osg::Vec3( .5,  .5, -.5)); // 6
 box-setVertexArray(vertices);

 // Normals
 osg::Vec3Array* normals = new osg::Vec3Array;
 normals-push_back(osg::Vec3( 0, -1,  0));
 normals-push_back(osg::Vec3( 0, -1,  0));
 normals-push_back(osg::Vec3( 0, -1,  0));
 normals-push_back(osg::Vec3( 0, -1,  0));

 normals-push_back(osg::Vec3( 0,  0,  1));
 normals-push_back(osg::Vec3( 0,  0,  1));
 normals-push_back(osg::Vec3( 0,  0,  1));
 normals-push_back(osg::Vec3( 0,  0,  1));

 normals-push_back(osg::Vec3(-1,  0,  0));
 normals-push_back(osg::Vec3(-1,  0,  0));
 normals-push_back(osg::Vec3(-1,  0,  0));
 normals-push_back(osg::Vec3(-1,  0,  0));

 normals-push_back(osg::Vec3( 1,  0,  0));
 normals-push_back(osg::Vec3( 1,  0,  0));
 normals-push_back(osg::Vec3( 1,  0,  0));
 normals-push_back(osg::Vec3( 1,  0,  0));

 normals-push_back(osg::Vec3( 0,  1,  0));
 normals-push_back(osg::Vec3( 0,  1,  0));
 normals-push_back(osg::Vec3( 0,  1,  0));
 normals-push_back(osg::Vec3( 0,  1,  0));

 normals-push_back(osg::Vec3( 0,  0, -1));
 normals-push_back(osg::Vec3( 0,  0, -1));
 normals-push_back(osg::Vec3( 0,  0, -1));
 normals-push_back(osg::Vec3( 0,  0, -1));
 box-setNormalArray(normals);
 box-setNormalBinding(osg::Geometry::BIND_PER_VERTEX);

 // Faces
 box-addPrimitiveSet(new osg::DrawArrays(GL_QUADS, 0, vertices-size()));

 // Colors
 osg::Vec4Array* colors = new osg::Vec4Array;
 colors-push_back(osg::Vec4(1,1,1,1));
 box-setColorArray(colors);
 box-setColorBinding(osg::Geometry::BIND_OVERALL);

 // Text Coords
 osg::Vec2Array* tx = new osg::Vec2Array;
 tx-push_back(osg::Vec2( 0.f, 0.f)); // 0
 tx-push_back(osg::Vec2( 1.f, 0.f)); // 3
 tx-push_back(osg::Vec2( 1.f, 1.f)); // 5
 tx-push_back(osg::Vec2( 0.f, 1.f)); // 1

 tx-push_back(osg::Vec2( 0.f, 0.f)); // 1
 tx-push_back(osg::Vec2( 1.f, 0.f)); // 5
 tx-push_back(osg::Vec2( 1.f, 1.f)); // 7
 tx-push_back(osg::Vec2( 0.f, 1.f)); // 4

 tx-push_back(osg::Vec2( 0.f, 0.f)); // 0
 tx-push_back(osg::Vec2( 1.f, 0.f)); // 1
 tx-push_back(osg::Vec2( 1.f, 1.f)); // 4
 tx-push_back(osg::Vec2( 0.f, 1.f)); // 2

 tx-push_back(osg::Vec2( 0.f, 0.f)); // 3
 tx-push_back(osg::Vec2( 1.f, 0.f)); // 6
 tx-push_back(osg::Vec2( 1.f, 1.f)); // 7
 tx-push_back(osg::Vec2( 0.f, 1.f)); // 5

 tx-push_back(osg::Vec2( 0.f, 0.f)); // 6
 tx-push_back(osg::Vec2( 1.f, 0.f)); // 2
 tx-push_back(osg::Vec2( 1.f, 1.f)); // 4
 tx-push_back(osg::Vec2( 0.f, 1.f)); // 7

 tx-push_back(osg::Vec2( 0.f, 0.f)); // 3
 tx-push_back(osg::Vec2( 1.f, 0.f)); // 0
 tx-push_back(osg::Vec2( 1.f, 1.f)); // 2
 tx-push_back(osg::Vec2( 0.f, 1.f)); // 6
 box-setTexCoordArray( 0, tx );

 return box;
}

osg::Node* createModel()
{
osg::Group* root = new osg::Group;

osg::ref_ptrosg::Geode geode = new osg::Geode;
osg::Geometry 

Re: [osg-users] newbie texture question

[David Cofer]

A previous post suggested I try something other than a bmp. So just to make 
sure it was not my image I tried a different jpg instead and it worked fine.  I 
then went back and tried it just using the standard osg::box and it worked as 
well. So It looks like the bulk of my problems was the image I was trying to 
map to the objects. I don't understand why, but bmp's, or my specific bmp, do 
not work well for some reason. I believe this solves my problems with this 
issue.

Thanks
David

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Re: [osg-users] newbie texture question

[Robert Osfield]

Hi David,

The osg::ShapeDrawable classes is only simply convenience classes, it
isn't able to map all the possible combinations of the way you might
want to apply.  For fine control you have to use osg::Geometry to
build up the coordinates and texture coordinates yourself.  See the
osggeometry example.

Robert.

On Fri, Feb 19, 2010 at 10:42 PM, David Cofer dco...@mindcreators.com wrote:
 Hi,

 I am new to OSG and I am attempting to port some work that was done in 
 directX over to OSG. I am using some of the basic geometric objects like 
 osg::box and osg::sphere. I got those working like I wanted, but when I tried 
 to add texture mapping to them the results are very different than what I got 
 in DirectX. For example, by default in directX when I mapped a texture  to a 
 box then each face got a full copy of the texture. However, when I map the 
 same texture to the box in osg I get some weird stretched lines over the 
 faces.

 Do the standard geometric objects not have texture coordinates already 
 defined, or am I doing something simple wrong? I have listed a code snippet 
 below. I have also tried using all of the different texture modes, and none 
 of them really worked.
 Do I have to set the texture coords up manually? Seems to defeat the purpose 
 of having simple objects predefined if I have to do a bunch of manual texture 
 corrdinate code for each one.

 I have attached an image example showing the difference between the directx 
 and osg versions.


 Code:

        osg::ref_ptrosg::MatrixTransform gNode = new 
 osg::MatrixTransform(osg::Matrix::translate(osg::Vec3(0, 0,0)));
        osg::ref_ptrosg::ShapeDrawable boxDrawable = new 
 osg::ShapeDrawable(new osg::Box(osg::Vec3(0,0,0), 10, 10, 10));
        osg::ref_ptrosg::Geode box = new osg::Geode;
        box-addDrawable(boxDrawable.get());
        gNode-addChild(box.get());
        root-addChild(gNode.get());
        osg::ref_ptrosg::Image image = osgDB::readImageFile(gravel.bmp);
        osg::StateSet* state = box-getOrCreateStateSet();
        state-setTextureAttributeAndModes(0, new osg::Texture2D(image.get()));




 Thank you!

 Cheers,
 David

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Re: [osg-users] newbie texture question

[David Cofer]

Ok. I still think it is silly that the default implementation does not produce 
a basic texture mapping, but I will accept that. However, I also tested a 
texture mapping using a loaded .obj file. It has the explicit u,v texture 
coordinates defined in the file, but it still does not work. I have to be 
missing something here. I have attached a picture of what I get for this obj 
file in directx vs osg, and I have attached the code and model I am using. Am I 
doing something wrong that the texture coordinates are messed up or something? 
Why are they not working correctly in OSG?

Thanks
David

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Re: [osg-users] newbie texture question

[Alberto Luaces]

David Cofer writes:

[...]

 I also tested a texture mapping using a loaded .obj file. It has the
 explicit u,v texture coordinates defined in the file, but it still
 does not work. I have to be missing something here.

Yes. There is no need to create an StateSet here. The problem is that
your .mtl is incomplete. It doesn't mention what file are you using as
texture. Just add this line at the end of Thorax.mtl:

map_Kd GrasshopperTexture.bmp

You can also use just the osgviewer program in order to test your models
like this:

osgviewer Thorax.obj

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Re: [osg-users] newbie texture question

[David Cofer]

I added the recommended line to the mtl file and it did apply the texture to 
the object this time, but it was still incorrect compared to what is seen in 
directx. See picture. I tried a couple of the options for the map_Kd command 
and none helped. 

Also, this will not help me in the long run becuase my final application has 
the option of allowing the user to specify the image file they want to use as a 
texture for their objects. This means I will need to re-apply the texture at 
runtime, and not load it in from the mtl file. I believe that requires the use 
of the stateset objects, which are not working correclty for me. 

Thanks,
David

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[osg-users] newbie texture question

[David Cofer]

Hi,

I am new to OSG and I am attempting to port some work that was done in directX 
over to OSG. I am using some of the basic geometric objects like osg::box and 
osg::sphere. I got those working like I wanted, but when I tried to add texture 
mapping to them the results are very different than what I got in DirectX. For 
example, by default in directX when I mapped a texture  to a box then each face 
got a full copy of the texture. However, when I map the same texture to the box 
in osg I get some weird stretched lines over the faces. 

Do the standard geometric objects not have texture coordinates already defined, 
or am I doing something simple wrong? I have listed a code snippet below. I 
have also tried using all of the different texture modes, and none of them 
really worked. 
Do I have to set the texture coords up manually? Seems to defeat the purpose of 
having simple objects predefined if I have to do a bunch of manual texture 
corrdinate code for each one.

I have attached an image example showing the difference between the directx and 
osg versions.
  

Code:

osg::ref_ptrosg::MatrixTransform gNode = new 
osg::MatrixTransform(osg::Matrix::translate(osg::Vec3(0, 0,0)));
osg::ref_ptrosg::ShapeDrawable boxDrawable = new 
osg::ShapeDrawable(new osg::Box(osg::Vec3(0,0,0), 10, 10, 10));
osg::ref_ptrosg::Geode box = new osg::Geode;
box-addDrawable(boxDrawable.get());
gNode-addChild(box.get());
root-addChild(gNode.get());
osg::ref_ptrosg::Image image = osgDB::readImageFile(gravel.bmp);
osg::StateSet* state = box-getOrCreateStateSet();
state-setTextureAttributeAndModes(0, new osg::Texture2D(image.get())); 




Thank you!

Cheers,
David

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