Finally added Quat support for my project, wasn’t that hard. Anyway, I understood how you can use 1 quat to define rotation, but what happens if I multiply this quat with another. As far as I understand, I must take in account that axis are affected by 1st quat, am I wrong? Then, when I create quat from given axis and angle, I calculate v, where every coordinate is given axis coordinate*sin(ang/2), I tried to normalize this v at the end of procedure & everything went wrong, without normalization everything is fine, why that so. Does that mean quat could be (x>1,y>1,z>1,w=any)?

And bonus question : are quats fater than glRotatef()? I know the difference should be around 0.1e10, but I’m qurios

I assume you are using quaternian multiplication. And that the order in which you multiply matters as in a*b not eq b*a you need to keep things normalised, are you sure you are normalising correctly?