glUniformMatrix4fv

The `glUniformMatrix4fv` function is a part of the OpenGL Shading Language (GLSL) and OpenGL API, used to upload a 4×4 matrix to a uniform variable within a shader program. Uniforms are variables in GLSL shaders that remain constant across all instances of a shader invocation, making them ideal for passing data such as transformations, lighting parameters, or projections that do not change frequently.

The function takes several parameters: the first specifies the location of the uniform variable in the shader program, which is typically obtained using `glGetUniformLocation`. The second parameter is a flag indicating whether the matrix should be transposed before being sent to the shader. Transposing is often unnecessary for model-view and projection matrices but may be required for normal matrices. The third parameter is the number of matrices to be uploaded, though `glUniformMatrix4fv` is primarily used for a single matrix (value 1). The final parameter is a pointer to the matrix data, which must be in column-major order, a convention commonly used in OpenGL.

This function is designed to work with floating-point matrices (`float` type in GLSL), ensuring compatibility with standard OpenGL rendering pipelines. It is commonly used in conjunction with other OpenGL functions like `glUseProgram` to dynamically update shader parameters during rendering, enabling techniques such as camera movement, object scaling, or lighting adjustments without recompiling the shader.

While `glUniformMatrix4fv` is widely supported in modern OpenGL versions, alternatives like `glUniformMatrix4x3fv` or `glUniformMatrix3x4fv` exist for non-square matrices, though they are less common. For newer OpenGL versions, Vulkan or Metal APIs may offer more modern alternatives, but `glUniformMatrix4fv` remains a fundamental tool for real-time graphics programming.