[Flightgear-devel] Sea color (was: Re: Regional textures merge request)

[Renk T. <tho...@jy...>]

> Hmm I've got something wrong here then - if I understand that right I  
> select
> Advanced Weather,  and skydome and the sea colour stuff should run? I get
> this:
>
> http://dl.dropbox.com/u/57645542/fgfs-screen-190.png
>
> It doesn't seem to have any interpolation.

The color seems about right to me for what the interpolation should give at the location. There is no interpolation in the scene, because the color change is assumed to happen on a 1000 km scale, so it changes smoothly for the whole scene as a function of position - take the ufo, fly 1000 km away from TNCM, compare sea color and it should go back to the darker blue-green default. Admittedly I haven't really tried flying 1000 km, I've just tested it on startup in different locations. Try starting at Nice (LFMN), that should have a dark blue.

> I was thinking of this for loop
 
> for (var i = 0; i < ivector_size; i = i + 1)
 
> I take the view that any for loop is not good, but if  ivector_size is
> small, I guess it won't matter.

It depends on what is executed in the loop. If it's a distance computation or property tree access, then there shouldn't be much more than 20 operations per frame. But I've done benchmark tests with basic math - say the sine function. Here, I could execute about 1.000 operations per frame without creating a measurable slowdown. In this particular loop, it's just adding numbers - that's probably a factor 100 cheaper than computing a sine, so if my benchmark extrapolates correctly, you can run it ~100.000 times per frame before running into trouble.

In practice, I think it's unlikely that we'll use more much than 100 points.

I have been coding some performance-eating stuff (and even some badly designed performance eating stuff), but that's not one of these cases.

Cheers,

* Thorsten