Monday, October 29, 2007

Optimal Performance for apt.dat Layout

I don't actually know all of the best ways to make an apt.dat file. The format is new and we haven't had a ton of time to performance test it. But here are some thoughts:
  • One thing I know is best to describe the shape you are using with the fewest number of nodes possible. In other words, let bezier curves do their thing, don't add a ton of vertices to them. And please don't add vertices to try to make the curves smoother. The best thing is to leave the layout simple and let X-Plane render it. In the future we will allow the user to set the level of smoothness based on his or her hardware. Adding more nodes will hurt quality - we will be able to pick better nodes at runtime than you can in the apt.dat file.
  • Avoid overlapping large areas of pavement. Overlap is bad - it hurts framerate by requiring the graphics card to draw the same pixels over and over. As X-Plane supports more advanced shaders for nicer lighting, this cost will be a lot heavier on users.
  • Ignoring overlap, the question of whether to have several smaller chunks of pavement vs. one large one is a difficult question. I would suggest moderation - try not to make too many individual pavement elements, but don't make the entire element one giant pavement either. You may have to experiment to find the best framerate.

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