OpenGL, C++ or C, And something to help with the rendering like SDL2 or GLEW or GLFW. NO GLUT!
Additional Info
Hello, I would like to learn OpenGL from the masters or experienced. I would like to have a friendly relationship with the job taker. I am a pretty fast learner. My primary goal is to learn about voxel worlds how how they are made. Ask me a question or send me an offer down below. We will be able to further talk on Skype if needed. I look forward to working with you soon :)