Re: [plib-users] Hidden Line Removal

[Steve B. <sjb...@ai...>]

Wolfram Kuss wrote:
> 
> Devrim Erdem <de...@in...> wrote:

> >We need to implement some sort of hidden line removal for our terrain
> >model in wireframe mode.
> 
> Citing from the red book, topic hidden-line removal (look into the
> index):
> "If you want to draw a wireframe object with hidden lines removed, one
> approach is to draw the outlines using lines, and then fill
> the interiors of the polygons making up the surface with polygons
> having the background colour".

You can do a little better than that with a two-pass trick.

Pass 1: Render all the geometry in completely transparent polygons
        ...make sure you have glAlphaFunc set so that the DO actually
        render.  As an alternative, you could draw the scene with it's
        'normal' alpha values - but tell GL to mask off the colour planes.

Pass 2: Use glPolygonOffset to move everything a tad closer to the eye
        and then re-render the geometry in wireframe mode.

The first pass sets the Z buffer as if it had been drawn normally - the
second pass does the actual rendering of the wires - which will be occluded
by the polygons in the first pass.

> BTW, the list is now at:
> pli...@li...
> While you are writing to woodsoup. Is the woodsoup-list still open?

Well, I've had no success in getting the Woodsoup maintainer to shut
them down...so probably they are still running.  However it's unlikely
anyone could find them because the Woodsoup website just redirects you
to our usual Slashdot location.  I suppose some older Linux CD's still
tell you to send queries to Woodsoup - it's hard to do anything about
that.  I suppose that's a good reason to let the Woodsoup mailing lists
live - we can at least tell people where they *SHOULD* be subscribed.

 
-- 
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