tmat3x4< float, lowp > lowp_mat3x4
3 columns of 4 components matrix of low precision floating-point numbers.
tmat3x4< float, highp > highp_mat3x4
3 columns of 4 components matrix of high precision floating-point numbers.
tmat3x4< float, mediump > mediump_mat3x4
3 columns of 4 components matrix of medium precision floating-point numbers.
OpenGL Mathematics (glm.g-truc.net)