Hi Shahar,
answers below.
Sebastian Messerschmidt wrote:
Hi Shahar Kosti:
As you don't provide any exact numbers I can only guess. But usually I'd
bind one or more textures per tile of paged set.
Depending on your hardware bind of 8192x8192 textures is no problem.
Can you be a bit more specific on how big the set is?
Also for the hidden textures - I don't really get what you mean. My best
guess is, that you mean not displayed.
Therefore write a custom fragment shader and bind the data-textures
along with you diffuse or whatever textures to the stateset of the tile.
As the fragment shader is fully programmable, it is your choice what is
done with the data.
cheers
Sebastian
Hi Sebastian,
Sorry for my late reply, it took me some time to get the data.
One TXP I'm currently looking at, represents a 3000 km² area with texture
resolution of 5m/pixel. Some areas have better resolution, up to 10 cm/pixel.
The additional metadata has similar resolution. So obviously wouldn't fit on a
single texture.
Okay, so the single TXP file represents the whole area? That's kinda
hard, I thought you have multiple tiles representing parts of your
complete data set.
Anyways, First of all, your data sets need to be aligned somehow.
Regarding your suggestions, could you elaborate on the "bind one or more textures
per tile of paged set" approach?
My current approach (which doesn't work), is to intercept paged nodes using a
custom ReadFileCallback, which runs a NodeVisitor. The visitor finds all Geode
objects and then the underlying geometries. I can bind a new texture to these
geometries, but I'm not sure how to set the values correctly.
You don't really need to bind at a level this deep. Usually if the
"terrain tile" is loaded and represent a LOD you want to work with, you
can simple add your data texture(s) as uniform to the stateset of the tile.
Given you have a texture with the data-image called "texture" you can do
it this way in your callback:
osg::StateSet* state_set = node->getOrCreateStateSet();
osg::Uniform* sampler = new osg::Uniform("MyDataSamper", 2
/*texture unit*/);
state_set->setTextureAttribute(unit, texture ,osg::StateAttribute::ON);
state_set->addUniform(sampler);
With this you bind the texture to a sampler for your shader, at the
texture unit 2. Depending on how many textures are already bound you
might need to modify the unit.
In the fragment shader you can now access the texture via:
uniform sampler2D MyDataSampler
..
..
main()
{
vec2 tex_coord = gl_TexCoord[0].st;
vec4 data = texture2D(MyDataSampler, tex_coord);
}
Each texel in the new texture, should be set based on the world location of the
corresponding texel in the current geometry texture. I'm not sure how to do
that using the geometry vertex and texture coordinate indices.
I hope this is clear enough.
This is a different question. If your terrain-data already contains a
base texture (like a satellite photo), the gl_TexCoord[0] might be
matching already.
If not you might want to use texture coordinate generation in the vertex
shader to get world-space texture coordinates.
It totally depends on your data.
For a first try, I'd load a dummy texture for each tile and pass it to
the gl_FragColor in the fragment shader to see how your coordinates are.
cheers
Sebastian
Thanks for the help,
Shahar
------------------
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http://forum.openscenegraph.org/viewtopic.php?p=54810#54810
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