Here are the top 20 most commonly used OpenGL API calls, organized by category:

## **Core Rendering Functions**
1. **glDrawArrays()** – Draw primitives from array data
2. **glDrawElements()** – Draw primitives using indexed arrays
3. **glClear()** – Clear buffers with specified values
4. **glViewport()** – Set viewport dimensions
5. **glEnable()/glDisable()** – Enable/disable OpenGL capabilities

## **Shader and Program Management**
6. **glCreateProgram()** – Create shader program object
7. **glUseProgram()** – Set active shader program
8. **glGetUniformLocation()** – Get location of uniform variable
9. **glUniform*()** – Set uniform variable values (int, float, mat, vec)

## **Buffer Management**
10. **glGenBuffers()** – Generate buffer objects
11. **glBindBuffer()** – Bind buffer object to target
12. **glBufferData()** – Initialize buffer object data
13. **glVertexAttribPointer()** – Specify vertex attribute data

## **Vertex Array Objects**
14. **glGenVertexArrays()** – Generate VAO objects
15. **glBindVertexArray()** – Bind VAO for subsequent operations

## **Texture Management**
16. **glTexImage2D()** – Specify 2D texture image
17. **glTexParameteri()** – Set texture parameters
18. **glActiveTexture()** – Select active texture unit

## **State Management**
19. **glGetError()** – Check for OpenGL errors
20. **glFinish()** – Block until all GL operations complete

These functions cover the fundamental operations needed for most 3D rendering applications using OpenGL. The exact choice depends on your specific rendering pipeline and requirements.