GLSL's transpose alternative in GLSL ES?

Question

I was trying to convert GLSL to GLSL ES and got this problem: transpose function isn't available in GLSL ES.

mat3 yuv = transpose(yuv_matrix);

So how I can use it? Is there any alternative?

Answer 1

A 3x3 matrix can be transposed as follows:

mat3 yuv = mat3(
    vec3(yuv_matrix[0].x, yuv_matrix[1].x, yuv_matrix[2].x),
    vec3(yuv_matrix[0].y, yuv_matrix[1].y, yuv_matrix[2].y),
    vec3(yuv_matrix[0].z, yuv_matrix[1].z, yuv_matrix[2].z));

Note, the transposed matrix is a matrix which is flipped over its diagonal.

(a  b  c) T    (a  d  g)
(d  e  f)    = (b  e  h)
(g  h  i)      (c  f  i)

Matrices consist of column vectors. So a matrix can be initialized by vectors, e.g.:

vec3 a, b, c;
mat3 m = mat3(a, b, c); 

And the vectors of the matrix can be accessed by the index operator, e.g.:

mat3 m;
vec3 v = m[1];