Re: [plib-users] Hidden Line Removal

[Wolfram K. <w_...@rz...>]

Steve wrote:

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

Interesting. You effectively "reversed" the passes and in one pass,
you don't draw to the colour buffer. I guess on some renderers this is
faster, but on most hardware it shouldn't matter since Z + colour + at
least one texture is done in one cycle.

BTW, we UHammes Software) still use an hidden line algo that really
calculates the occlusions like in "face i occludes line j from t=0.32
to 0.647" :-(. I think it should be trivial for us to use opengl for
doing this to the screen. But we still need the old algo for plotters
:-(.


> the Woodsoup website just redirects you
>to our usual Slashdot location.  

LOL ;-).

> 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.

Yes, I agree.

Bye bye,
Wolfram.