Loading custom data into custom shader uniform

[trinhtuanlong]

I have a shape file containing the buildings in the map I want to render. I have manipulated the shape file to add an additional tag to each building specifying the material of that building (glass, concrete,...). Now I want to load this information as a uniform into my custom shader and use it there (say glass is int 1, concrete is int 2,...). All of this must be done using the API and no .earth files. How do I do this? I have looked at all the examples but there does not seem to be anything similar.

[gwaldron]

There is nothing in osgEarth to support this. What are you planning to do in the shader?

[gwaldron]

You will need to generate the building geometry with your own code to add either the uniform or the custom vertex attributes.

[trinhtuanlong]

How do I generate these geometries? Given a .shp file how do generate the geometries? Is there an example code somewhere?
As a side note, I have a .tif file containing the heatmap, and now I want to use it as a texture in my virtual program. How do I do this? How do I get the uniform sampler and the texCoord?

[gwaldron]

BuildGeometryFilter is the class in osgEarth that builds geometries from features. You might be able to modify it to add your custom vertex attributes.

There is nothing special about VirtualProgram when it comes to uniforms, etc. Just reference them in your GLSL code as usual, and add them to the osg::StateSet as you normally would.

Is your TIFF georeferenced? Do you plan to add it as a GDALImageLayer?

[trinhtuanlong]

Thank you for the reply. The file was a geoTIFF, and it is georeferenced. Currently I am adding it to my application as a GDALImageLayer. Now how do I use it in my custom shader? Does OSG Earth provide a uniform sampler for this Layer already or do I have to create it myself? For the texture coordinate do I have to calculate the coordinate myself or is there a built-in reference variable, perhaps oe_layer_tilec? If I do not add this geoTIFF file as an imageLayer, and add the image as a texture then do I have to perform the coordinate transform myself? Or is there a way for OSG Earth to handle this? The tiff is indeed georeferenced, when I view it in some tiff viewer in already points at the correct coordinate.

[gwaldron]

You can expose it as a shared layer. Check out this example earth file.

Basically you mark the layer as shared and give a name to its sampler and matrix uniforms. Then in the shader you will import both the sampler and its matrix using the oe_use_shared_layer pragma.

oe_layer_tilec holds the tile coordinates [0..1] for the currently rendered tile, so you can multiply that by the texture matrix to sample the texture.

Hope this helps :)