sky rendering

[joevenzon]

it looks like (and i haven't looked at the code yet) the horizon model gets projected outward from the origin

instead of projecting the horizon on the sky, we can mark it as relative to the viewpoint position. how hard would it be to implement this?

I don't quite follow what you mean by these statements... but I'll try to explain how the sky and horizon are rendered in VDrift.

First of all, any objects not marked as "skybox" get rendered at the origin. Originally there was a way to add a fixed offset, but that's not really supported anymore. All positioning data is stored in the coordinates of the objects themselves. Let's walk through an example. A vertex at 100,0,0 with the camera at 90,0,0 is drawn at the (zero offset) origin 0,0,0 plus the vertex coordinate 100,0,0 minus the camera position 90,0,0 equals 10,0,0. Take a second to look that over... it makes sense, because it means that when the camera is close to an object, the object looks closer.

Second, all objects marked as "skybox" get rendered at the origin (like above) but do not take into account the camera position. This means that a vertex at 100,0,0 with the camera at 90,0,0 is drawn at 0,0,0 plus vertex coordinate 100,0,0 equals 100,0,0. This makes sense, because it means that no matter how far you drive, the sky still looks like it's the same distance away.

Note that for simplicity I ignored the camera rotation in the examples above (so basically the camera is facing exactly forward).

VDrift used to allow you to mark objects as skybox and full bright separately, so you could have a skybox that is lit normally (blech) or a normal object that has no lighting and is always bright. I took that feature away thinking no one wanted it and now assume that all skyboxes are fully lit and everything that isn't a skybox is lit. If you want me to go back to the old system of allowing separate flags, let me know.

In fact, all of this code is pretty easy to change, so if it makes your life easier, let me know what you want and I'll set it up.