Column major matrices

[glyh]

OpenGL uses column major matrics so in order to combo well with OpenGL I suppose it would be nice to have a column major version of matrices?

[ikskuh]

The matrixes should work out of the box as-is with OpenGL. Did you encounter any problems?

[glyh]

We're using row major matrices AFAIK, so computation does not work seemlessly with openGL.

For example, there's an old demo of someone using zlm to replcate learnopengl tutorial's lesson on transformation.

Here's the code.

Pay attention to this line:

https://github.com/Flecart/zig-learnopengl/blob/2bd30f3286a99c825023bcec2199dba770b8315a/src/chapter-5/5.1.zig#L195

You see the order of multiplication is incorrect. But exchanging the order yields the wrong result.

[terraquad]

I think you can just call Mat4.transpose() to get column-major matrices.

[martician1]

To add to @terraquad 's answer, you can also let OpenGL transpose the matrix for you by passing GL_TRUE to the transpose parameter of the glUniformMatrix* family of functions:

void glUniformMatrix4fv(
    GLint location,
    GLsizei count,
    GLboolean transpose, // <- this controls whether the matrix should be transposed
    const GLfloat *value);

[martician1]

Also, I think the original implementation uses column major matrices. See the translation matrix for example.

The code snippet you linked here

We're using row major matrices AFAIK, so computation does not work seemlessly with openGL.

does standard matrix multiplication and that's valid for column major matrices, since the result of $M^T * N^T$ should be $(N * M)^T $ and not $(M * N)^T$ (It may seem like this will reverse the order in which matrices are applied to a vector but it doesn't because vector matrix multiplication is implemented with the vector on the left of the matrix and in row form - $(v_0, v_1, v_2, v_3) * Transform$)