Multiplying a matrix and a vector in GLM (OpenGL)

I have a transformation matrix, m, and a vector, v. I want to do a linear transformation on the vector using the matrix. I'd expect that I would be able to do something like this:

glm::mat4 m(1.0);
glm::vec4 v(1.0);
glm::vec4 result = v * m;

This doesn't seem to work, though. What is the correct way to do this kind of operation in GLM?

Edit:

Just a note to anyone who runs into a similar problem. GLM requires all operands to use the same type. Don't try multiplying a dvec4 with a mat4 and expect it to work, you need a vec4.

2 Answers

glm::vec4 is represented as a column vector. Therefore, the proper form is:

glm::vec4 result = m * v;

(note the order of the operands)

Since GLM is designed to mimic GLSL and is designed to work with OpenGL, its matrices are column-major. And if you have a column-major matrix, you left-multiply it with the vector.

Just as you should be doing in GLSL (unless you transposed the matrix on upload).