How to update shader code outside the shader in a for-loop with glGetUniformLocation() and glUniform3f()?

[MBD]

Hi, I am trying to do this learnopengl tutorial (HDR):

LearnOpenGL - HDR

I saw that they used the following for-loop to update the variables in the shader code:

    for (unsigned int i = 0; i < lightPositions.size(); i++)
    {
        shader.setVec3("lights[" + std::to_string(i) + "].Position", lightPositions[i]);
        shader.setVec3("lights[" + std::to_string(i) + "].Color", lightColors[i]);
    }

Now, I want to know if this is also possible by using glGetUniformLocation() and glUniform3f(). I tried this (first, just with the lightPositions and using an array instead of a vector):

int size = sizeof(lightPositions) / sizeof(float3);
  for (unsigned int i = 0; i < size; i++)
  {
    int pos_loc = glGetUniformLocation(light_program_handle, "lights[" + std::to_string(i) + "].Position");
    glUniform3f(pos_loc, lightPositions[i].x, lightPositions[i].y, lightPositions[i].z);
  }

But I got an error message regarding glGetUniformLocation() because of the parameter-list-definition of the function itself when I try this? Help is very much appreciated!

[Alfonse_Reinheart]

@MBD

Now, I want to know if this is also possible by using glGetUniformLocation() and glUniform3f().

That is almost certainly what those functions are doing under the hood.

[GClements]

@MBD

But I got an error message regarding glGetUniformLocation() because of the parameter-list-definition of the function itself when I try this?

That’s because you’re passing a std::string, but OpenGL (being C, not C++) wants a char*. Use the .c_str() method.