I'm trying to write a program to convert a quaternion to a rotation matrix. One source I found is: http://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation#Conversion_to_and_from_the_matrix_representation
I am pretty sure that for the variable names, a=w, b=x, c=y, d=z, but that doesn't explain the fact that the two matrices look completely different. When I try to implement them, the second one looks right whereas the first one looks wrong. What is the difference between the two matrices?