What does sampler2D store?

Question

I\'ve read a texture example in OpenGL 2.1. The fragment shader looks like this:

#version 120

uniform sampler2D texture;
varying vec2 texcoord;

vo         


        

Answer 1

The sampler2D is bound to a texture unit. The glUniform call binds it to texture unit zero. The glActiveTexture() call is only needed if you are going to use multiple texture units (because GL_TEXTURE0 is the default anyway).