How to build a circuit in gazebo [Update visuals at runtime]

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Hi all, I am trying to build a circuit in Gazebo but I don't know how I can manage this task. In particular I don't know if I have to Necessarily create a .world file or I can just create a texture for example. I have an image of this circuit and also I can have a gis file, could these files help me? Someone had already faced with this kind of work?

Thanks in advance.

[copied from comments by moderator] I am sorry if I was so inaccurate. I am using Gazebo7 without ROS and I am writing some code for path plannig in autonomous cars scenario. As clarified today by my Ph.D. tutor I just have to update the ground plane texture at runtime. More in detail: I have a module that using Gazebo messages (I don't already know which ones) sends at certain time intervals an image that represents the actual state of the road (for example lanes) and I just want that Gazebo draws for me the new road

UPDATE

Hi all and Hi Peter, I tried to do do what you said but I am not sure that I have done the right things (in fact it doesn't work).

Actually I started from the tutorial at http://gazebosim.org/tutorials?tut=cu... to manage the messages and from your code to update the model.

More precisely:

1: I build a world in which I put a ground model with the texture that I have to modify at runtime.

2: I used all the code that I linked to manage the message exchange but in the function create() I put the code of my interest. I used this function because it seems that is the function that performs the operation when a message arrives. I modified the function in the following way (I commented the initFile because I don't know the perfect meaning and I don't know how to use it and if I have to use it):

 public: void create(CollisionMapRequestPtr &msg)
  {

  std::cout << "Received message" << std::endl;
  modelSDF.reset(new sdf::SDF);
  std::cout << "After Reset"<<std::endl;
  // sdf::initFile("root.sdf", modelSDF);
  sdf::readFile("~/.gazebo/models/my_ground_plane/model.sdf", modelSDF);
  std::cout<< "After reading"<<std::endl;
  world->InsertModelSDF(*modelSDF);
  std::cout << "After inserting"<<std::endl;
  }

Obviously the prints are useful just for debug. As to me it seems to be reasonable.

3:I send a message as shown in the tutorial and before to send it I change the image that I would like use as new texture (is an image exchange so I change the file but I use the same name).

4: I receive the following output (wrong and I have texture no update):

Subscribing to: ~/collision_map/command
[Err] [Scene.cc:2927] Light [sun] not found. Use topic ~/factory/light to spawn a new light.
Received message
After Reset
Error [parser.cc:286] Error finding file [~/.gazebo/models/my_ground_plane/model.sdf].
After reading
After ...