drawing outerlines for concave polygons

bhogasena · January 29, 2009, 4:46am

hi,
i rendered the filled concave polygons by tesselation.now i have to draw outerlines for those filled polygons. can any one help me for this, so that i’ll be thankful to you.
thanks and regards
k.bhogasena reddy

Brolingstanz · January 29, 2009, 7:29am

On Windows, check out wglUseFontOutlines. I think it uses one of the “plane sweep” algorithms to triangulate the contours.

Or maybe have a look at one of the (platform neutral) font generation/rendering libraries out there. I’ve seen several mentioned in recent threads.

Hope it helps.

wedge · February 2, 2009, 9:24am

Use GL_LINE_LOOP with the original Polygon Points?

Ekh · February 2, 2009, 12:32pm

I would draw the polygon twice. The first time in the normal way and the second time, using glPolygonMode (GL_LINES) and with using wider lines (I think with using glPointSize).

wedge · February 3, 2009, 4:35am

Hm ok whats wrong here …
> using glPolygonMode (GL_LINES)
> using glPointSize
use LineWith and this can also be a solution BUT
you also draw the triangeles inside the polygon. But if you use Z-Buffer and polygonoffset you can remove the “wrong” lines inside …