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Member Since 17 Jun 2002
Offline Last Active May 02 2016 08:41 AM

Topics I've Started

Quad antialiasing problem

02 May 2005 - 08:41 PM

Hello, my program needs to draw large numbers of antialiased points. Unfortunately, FSAA is not an option, so I tried GL_POINT_SMOOTH. This turned out to be very slow on nVidia cards (as compared to 3dlabs cards, which only get a small performance hit). After fiddling around for some time, I found out that drawing the points as antialiased billboard quads was substantially faster. But when the billboards get larger, an ugly crack shows up between the two triangles of the quad (see sample image). It looks like the black background color is interpolated at the "inner" edge. This crack remains, no matter what primitive (GL_QUAD, GL_TRIANGLE_FAN, GL_TRIANGLE_STRIP, GL_POLYGON) I use to render the billboard. It also doesn't make a difference if I force the four billboard vertices to lie in one plane by looking down one coordinate axis and setting that component of the billboard base vectors to zero. I'm using glBlendFunc(GL_SRC_ALPHA,GL_ONE_MINUS_SRC_ALPHA). How do I get rid of that crack? Thank you for reading!