Map grabscreen() as texture onto 3D object

I am wondering how I can ‘bind’ a texture generated by the grabscreen() function onto a 3D object of which I imported in OBJ format using the ofxAssimpModelLoader. I am having problems trying to map textures onto them - somehow they dont show up. Maybe there is no mesh to bind the texture onto?

My ultimate idea is to do some manual projection mapping calibration whereby I create graphics in openframeworks, grab the frames as a texture and place it on 3d surfaces of which I can position and rotate them later on.

Any ideas? I have a code that I started on below:

void ofApp::setup(){
Assimp3D.loadModel(“MonkeyhiRes.OBJ”);
Assimp3D.setPosition(ofGetWidth()/2,ofGetHeight()/2,-50);
Assimp3D.setScale(1,1,1);

}

//--------------------------------------------------------------
void ofApp::update(){
Test.grabScreen(100,100,100,100);
Tex = Test.getTextureReference();
}

//--------------------------------------------------------------
void ofApp::draw(){

ofFill();
ofSetColor(255,0,0);
ofCircle(100,100,100);
ofSetColor(0,255,0);

Tex.bind();
Assimp3D.drawFaces();
Tex.unbind();
}