v0.6.0

Briefing camera fixes for path tracing

v0.6.0 fixes two things you could see in Vulkan with Ray Tracing on.

The briefing's live camera shows its fog again. On Level 1 the camera view in the briefing's lower right showed the far hills and water sharp, with no haze. Level 1's remastered fog is a sky blue, and in that camera it disappeared into the water and sky. The camera now fades the distance into its own fog colour, as the original game and OpenGL do. Other worlds' briefings were already right and look the same.

No more white flash when the briefing camera opens, or when you arrive in a world. The briefing camera opens and closes with a zoom that starts and ends at zero, where it shows nothing. The path tracer still drew those frames, and they left the mist holding bright values that took 2 to 3 seconds to fade. You saw a white camera view that slowly cleared. After Start Mission, the same thing could make the world arrive over-bright. Those frames are no longer traced, and the next view's mist starts fresh.

OpenGL, the software renderer and Vulkan with Ray Tracing off are unchanged.