Here is our skymaps VS. As you can see, we are taking in normal values for each vertex still, this is because we are going to be using the same input layout for all our geometry (so we don‘t have to do more code). However, we will not be using the normals. And in fact, we did not define texture coordinates for our vertices either. This is because the texture coordinates will be defined by our vertices position. We can use our vertices position as a vector, describing the texel in our texturecube to color the pixel with. You can see how we do that with the line output.texCoord = inPos;. Also, notice when we are defining the output position, we take the values .xyww instead of .xyzw. This is because w is equal to 1.0f. We want to make sure our skymap is always the furthest object in our scene, so we want to set our z value to 1.0f too, which is what w is. Remember, 1.0f is the furthest value from the screen.

http://www.braynzarsoft.net/index.php?p=D3D11CUBEMAP