Re: [Gzz] Coordinates, shape

[Tuomas Lukka]

On Tue, Sep 10, 2002 at 12:41:54PM +0200, Benja Fallenstein wrote:
> Tuomas Lukka wrote:
> >>So,
> >>a) is that system ok for what you need in the demos? Or do you need 
> >>the more flexible approach already, where you can define clipping 
> >>independently from translation/transformation?
> >>   
> >>
> >
> >Yes, we need, and especially without any clipping but with stenciling.
> >
> 
> Ok, terminology problem: I see stenciling as a way to archieve 
> clipping-- what word would you use for the general concept (i.e., 
> drawing only the things inside a shape)?

Well, clipping is the usual term but its meaning has changed to mean
clipping to a polygon. How about "general clipping"?

> >Maybe we should make all clipping and stenciling explicit for now,
> >i.e. so that the view calls an utility routine that constructs
> >the clipped thing?
> >
> 
> So you would suggest to do it *not* by cs, but by vob? That sounds 
> difficult (would have to change the view hierarchy so that the lower 
> levels know what the higher levels need clipped).

Well, we don't have that many levels and don't really need them.

> Would this work: Ability to attach a "clipping/stenciling" vob to every 
> cs when created? When rendering the normal vobs, the clip/stencil 
> vob(s) of all coordinate systems upwards in the hierarchy would already 
> have been called. Or is that bogus?

It is: coordinate systems' hierarchy doesn't work that way in OpenGL.
The vobs are always put to OpenGL in the order they were put into
the vobscene.

> >>b) How do we implement it? I.e., what code does set the clip area? 
> >>(In AWT, the vob asks the VobRenderInfo for the clipping rectangle, 
> >>then issues the clipping command itself, but somehow I got the 
> >>feeling you won't like that for GL.)
> >
> >No, since with stencils, it can be of *any* shape, even defined 
> >by a shaded texture.
> >
> 
> Right, you want to use that already. Ok.

Yes, I have a specific visual in mind. Hmm, should probably draw it ;)

> >>>Actually, a good stopgap measure might be simply to render the 
> >>>characters
> >>>at size 2^n instead of something like "40" currently. That could
> >>>improve it considerably. Also, have you tried __GL_FSAA_MODE ?
> >>>It helps a little.
> >>>     
> >>>
> >>I don't know how to turn it on...
> >>   
> >>
> >
> >At the point where the actual GZZGL font is created it is given a pixel
> >size (texel size).
> 
> So how do I use that to turn __GL_FSAA_MODE on?
> 
> The GZZGL texel size is height? width? both?

These are two different things.
The texel size is the size given to freetype library.

__GL_FSAA_MODE is a property of the NVIDIA driver, and enabled by
the environment variable (see /usr/doc/nvidia-glx/README.gz)

        __GL_FSAA_MODE=4 make runXXX

However, I just noticed some stencil problems with this, which I will
have to look into.

        Tuomas