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c++openglglm-math

glUniform3fv not working OpenGL

I'm working on a piece of code in OpenGL. I'm getting the following error message while trying to compile:

MyGLWidget.cpp: In member function ‘virtual void MyGLWidget::initializeGL()’:
MyGLWidget.cpp:30:38: error: cannot convert ‘glm::vec3 {aka glm::tvec3<float, (glm::precision)0u>}’ to ‘const GLfloat* {aka const float*}’ in argument passing
MyGLWidget.cpp:31:39: error: cannot convert ‘glm::vec3 {aka glm::tvec3<float, (glm::precision)0u>}’ to ‘const GLfloat* {aka const float*}’ in argument passing

I have declared these locations in MyGLWidget.h as follows:

    GLuint llumLoc, focusLoc;

And have initialize them in MyGLWidget.cpp as:

  llumLoc = glGetUniformLocation (program->programId(), "llumAmbient");
  focusLoc = glGetUniformLocation (program->programId(), "posFocus");

"llumAmbient" and "posFocus" are uniforms in my vertex shader:

uniform vec3 llumAmbient;
uniform vec3 posFocus;

I get the mentioned error message while trying to call the following code inside of MyGLWidget::initializeGL

glUniform3fv(llumLoc, 1, glm::vec3(0.2));
glUniform3fv(focusLoc, 1, glm::vec3(1.0));

Obviously, I've tried to follow the documentation at www.opengl.org and glm.g-truc.net/0.9.2/api/a00001.html, but I just can't see what's wrong with this code...

Solution

  • You need to give a pointer to the vector, not the vector itself. For example:

    glm::vec3 v(1.0f);
glUniform3fv(focusLoc, 1, glm::value_ptr(&v[0]));