Quaternion Multiplication in a shader.

Hi All!

I have this math visualization project I am working on which involves stereo-graphically projecting points on the 4 dimensional sphere onto a 3D plane.

I have the prototype working great! (https://www.facebook.com/100008697402693/videos/1513084485658117/?theater)

Anyways, I'm trying to move most of the calculations I am doing off the CPU and onto the GPU. I have most of it working except I cannot for the life of me get quaternion multiplication to work in CG. I really need a function in CG that takes two float4's and multiplies them the same way the * operator works with Unity Quaternions.

The function I am using now looks like:

 float4 mulQuaternion(float4 q1, float4 q2)
                 {
                     float4 q =
                     {
                         (q1.w * q2.x) + (q1.x * q2.w) + (q1.y * q2.z) - (q1.z * q2.y),
                         (q1.w * q2.y) - (q1.x * q2.z) + (q1.y * q2.w) + (q1.z * q2.x),
                         (q1.w * q2.z) + (q1.x * q2.y) - (q1.y * q2.x) + (q1.z * q2.w),
                         (q1.w * q2.w) - (q1.x * q2.x) - (q1.y * q2.y) - (q1.z * q2.z),
                     };
                     return q;
                 }

I'm sure there is a small mistake somewhere, but I have been at this for a while and can't seem to fix it. Any help would be really appreciated. Thank you!