On Monday 09 January 2012 09:53:08 Stuart Buchanan wrote:
> Hi Thorsten,
>
> No, I don't think gl_Vertex.z will give you the cloud altitude. That's
> just the vertex position relative to the sprite center. glColor is
> used to pass in the sprite location relative to the cloud center, and
> the Model Matrix places the cloud relative to the rest of the scene.
>
> I don't think the Model matrix will help you much either, as IIRC
> (0,0,0) is the center of the earth spheroid.
>
> What do you need it for? sunrise/sunset lighting?
>
> As it happens, the Impostor changes will reduce the number of
> variables required by the shader significantly, so I could add it in
> as an additional variable if it would be useful.
>
> -Stuart
>
> On Mon, Jan 9, 2012 at 8:08 AM, <thorsten.i.r...@jyu.fi> wrote:
> > Hi Stuart,
> >
> > is gl_Vertex.z a reasonably approximate guess for the altitude in which
> > the cloud finally appears or do I have to look elsewhere? There's lots
> > of
> > reshuffling of the vertex coordinates going on in the shader, and I've
> > kind of lost track a bit...
> >
> > * Thorsten
> >
In the transition shader (and the other terrain shaders), using gl_Vertex.z
works as a good aproximation (it's used to determine if there should be snow
painted, sometimes it behaves funny, but it's generally reliable enough), but
for clouds maybe using the final value of gl_Position.z might give you what
you want?
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