C++/OpenGL glm Can't plug matrix into uniform in shader

Question

I can't use my matrix in my OpenGL shader; this is giving me an error:

glUniform4f(matLocation, mat[0], mat[1], mat[2], mat[3]); // glm mat4

no suitable conversion function from "glm::tvec4<float, glm::highp>" to "GLfloat" exists

I don't entirely understand why it's giving me this error message, and as usual, Googling doesn't give me any good results. Why would it want me to convert matrices to floats?

A matrix isn't a vec4, you should use glUniformMatrix4fv and glm::value_ptr. — pleluron, Dec 02 '16 at 23:57
Then why are you using glUniform4f? It sets the four values of a vec4. — pleluron, Dec 03 '16 at 00:06
As I said, glUniformMatrix4fv with the `value` argument being `glm::value_ptr(mat)` — pleluron, Dec 03 '16 at 00:11

score 1 · Accepted Answer · answered Dec 03 '16 at 00:28

1

glUniform4f only updates a vec4 with four float values, so you need glUniformMatrix4fv which takes a pointer to an array of 16 float values glm can provide with glm::value_ptr.

mat[n] only yields the nth column, a vec4; thus the compilation error.

answered Dec 03 '16 at 00:28

pleluron

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C++/OpenGL glm Can't plug matrix into uniform in shader

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