I know i already have the result. But i always like to how things actualy work, not the trick. Using the 0,-1,0,0 for me feels like using a trick.
What i always thought wrong was that filling in a,b,c,d had to do something with placing the clipping plane. But as sos said you can use gltranslatef and glrotatef for that.
I assume that the direction made with x,y,z can be represented by drawing a line from 0,0,0 to x,y,z
I i want to create a clipping plane using my camera point i should give that into a*x+b*y+c*z+d=0 so if the camera point is 1,6,1 that would make:
a*1+b*6+c*1+d=0
What steps to i take to get the unknown a,b,c, and d. Of Course i could fill them all with zero's but that would be dumb
) to scale the clipping plane, but all you are going to do is move it to a different position.