mesh vertex displacement

//get the current vertices of the sphere
vector<ofPoint> &sphereVerts = sphere.getMesh().getVertices();
//calculate how much to displace them
float extrusionAmount = sin(ofGetElapsedTimef() * deformSpeed) * extrusionRange;

for (int i=0; i<sphereVerts.size(); i++) {
  ofVec2f t = sphere.getMesh().getTexCoords()[i];
  t.x = ofClamp( t.x, 0, pixels.getWidth()-1 );
  t.y = ofClamp( t.y, 0, pixels.getHeight()-1 );
  //get the brightness of the pixel at that vertex's position
  float br = pixels.getColor(t.x, t.y).getBrightness();
  //multiply how much to displace it by the brightness
  sphereVerts[i] = origVertices[i] * (1 + br / 255.0 * extrusionAmount);
}