title: Is the texture normal calculated from the color of each texel of a texture?
body: <p>In the normal mapping, the texture used also has the texture normal in addition to the texture color, just like the following fragment shader code:</p>
  
  <pre><code>#version 420 core
  out vec4 color;
  // Color and normal maps
  layout ( binding = 0) uniform sampler2D tex_color;
  layout ( binding = 1) uniform sampler2D tex_normal;
  </code></pre>
  
  <p>But what I don't understand is that what type of image has that 'texture normal'?
  I also searched some solutions used to calculate the texture normal with it's RGB color:</p>
  
  <pre><code>Red maps from (0-255) to X (-1.0 - 1.0)
  Green maps from (0-255) to Y (-1.0 - 1.0)
  Blue maps from (0-255) to Z (0.0 - 1.0)
  </code></pre>