I am trying to implement the parallax scrolling in my XNA 3d game. However all information that I have found is always refered to 2d games. I have just implemented an octree in my game, so I have to add the differents "layers" of the parallax in the octree and then the problem start. I see multiple alternatives for implementing the parallax.
The first alternative is moving in the Octree the "layer" with the speed assigned to it as the player moves. The problem with this is that I have to update most of the Octree every time the player moves.
The second alternative is not modifing the Octree. Instead, I would modify the BoundingFrustum of the camera to adapt it to each layer. The problem is that I don't know if I can modify the BoundingFrustum and if I can modify it, I have to find the correct position of the layer rendering (it isn't the original position of the layer).
Is there a simpler alternative that I have just outlined? Or at least faster?
I don't really understand what you mean by parallax scrolling in 3D. The parallax effect in a 2D game is there to fake a 3D world, so you don't need it in a 3D game if you use a perspective projection. Please provide more information on what you're trying to achieve here.