Pass "uniform sampler2D" to glsl shader in libgdx(using modelBatch)

Question

I have trouble with passing sampler2d uniform from my code to shader. I have this line in my shader:

uniform sampler2D u_texture;

In code, I am using g3db models created in blender(with textures):

AssetManager assets = new AssetManager();
    assets.load(data+"/earth.g3db", Model.class);
    assets.finishLoading();
    Model earthModel = assets.get(data+"/earth.g3db", Model.class);
    earthPlanet = new ModelInstance(earthModel,0,-1,0);

I render this using modelBatch:

 modelBatch.begin(cam);
    modelBatch.render(earthPlanet, shader);
    modelBatch.end();

I have shader class in my code, and a render method within:

public void render(Renderable renderable) {
    program.setUniformMatrix(u_worldTrans, renderable.worldTransform);
        //how to pass texture??
    //program.setUniformf(sampler2D, ????);
    renderable.mesh.render(program,
            renderable.primitiveType,
            renderable.meshPartOffset,
            renderable.meshPartSize);
}

I would be happy for any response. Thanks!

Answer 1

Your confusion stems from the fact that you think you pass textures to sampler uniforms. This is not the case.

When you give a value to a sampler uniform, the value you are supposed to supply is the texture unit. Say you had a texture and bound it to GL_TEXTURE0, then you would give the sampler uniform the value: 0. Generally you treat samplers as integer uniforms, by the way, so the proper code would probably be: program.setUniformi (sampler2D, 0);

This tells GLSL that the sampler will use texture unit 0, the actual texture used will depend on whatever is bound to that texture unit.