Translating spatial coords to coords on its texture


I've found out how to paint small dots of black color on the walls, floor etc. in the model I'm working on. I have a point located on the floor, but how do I find the corresponding point on my texture (x,y)? Are there any convenience methods for this that I haven't found yet? I need to know which pixels to paint…

Here's what I'm trying to do…

      Vector3f intersection = new Vector3f();

      // Here's a large chunk of code where I find the point in the scene where I'm gonna paint (intersection)

      Spatial s = spatials.get(index);      
      TextureState ts = (TextureState)s.getRenderState(StateType.Texture);
      Graphics2D g2d = (Graphics2D)images[index].getGraphics();
      g2d.fillOval(0, 0, 3, 3); // Need to get the correct coordinates and replace (0,0)
      Texture newTex = TextureManager.loadTexture(images[index],
            Texture.MagnificationFilter.Bilinear, 1, false);
      ts.setTexture(newTex, 1);

Thanks in advance for any tip that might help  :)