I have a scene where I have a light going around the room. I want to draw a quad “around” that point, like a particle system. The problem is: what calculations must I do so that the quad is always paralel

to the viewer? I was thinking: I always know the point where the light is. Since I use gluLookAt, the first 6 parameters of gluLookAt give me the normal vector of the plane where the quad should be draw, so I can get: ax+by+cz+d=0. The four vertex for the quad must belong on this equation. But how do I get the 4 points out of the equation?

I hope I have explained myself properly…

Please help me…