【无标题】vertex shader and fragment shader
The vertex shader differs in its input, in that it receives its input straight from the vertex data.
The other exception is that the fragment shader requires a vec4 color output variable, since the
fragment shaders needs to generate a final output color. If you fail to specify an output color in your fragment shader, the color buffer output for those fragments will be undefined (which usually means OpenGL will render them either black or white).