OpenGL Mathematics (glm.g-truc.net) 
tmat3x2< float, highp > highp_mat3x2
3 columns of 2 components matrix of high precision floating-point numbers. 
tmat3x2< float, lowp > lowp_mat3x2
3 columns of 2 components matrix of low precision floating-point numbers. 
tmat3x2< float, mediump > mediump_mat3x2
3 columns of 2 components matrix of medium precision floating-point numbers.