OpenGLSkybox (CubeMap) movement along with camera movement

Question

I have been following some OpenGL tutorials for an open world project i am currently working on where the goal is to have an Openworld Scene with several objects (mountains etc...) present and with a SkyBox where all the objects are placed inside it.

I would like to ask if there is any way of the camera freely moving inside the skybox, "interacting" with potential objects in it, but without actually getting out of the boundaries of the box. In the tutorials the translation of the camera is removed, so it can only look around without moving around.

Is it a common practice to actually move the camera inside the skybox, or should i somehow move the skybox along with the camera, thus never reaching the boundaries of the box?

Answer 1

Skybox is usually rendered without offset to camera because its content represent stuff very far away (many times bigger than actual camera movement) like stars or mountains that are many kilometers away. So even if you move like 100 m in any direction the rendered result is not changed at all (or very little that can not be recognized).

If your skybox contains stuff you want to move towards than is doable but you need to limit the movement so you not get too close as that would result in pixelation of the skybox and eventually even crossing it. That can be done by game terrain (you can not jump above boundary mountains or swim too far from an island etc.

Another option is to limit camera distance from skybox center to some safe distance. If more far then the limit move the skybox to match the distance again... that way you can come near/far to skybox up to a point (it gets bigger/smaller on the close/far side) and never cross it ... without any actual camera position restrictions...

Answer 2

First things first, when you are rendering a sky box, generally, you don't render an actual box.

The skybox contains stuff that generally never or only very slowly change and is so far away that the player will never reach. The skybox is stored in a cube map texture and rendered through a full screen rectangle. In the shader you use OpenGL's cubemap sampling by sampling with the eye vector into the map.

If the skybox is dynamic, like dynamic time of day, it is only re rendered every couple of frames or only when needed.

A while back I wrote an article on how to do it: GLSL Skybox (You will need to update the code to a modern OpenGL version through...)