Communicating Other Data to a Shader

• When we want to send other data to a shader, we use uniform variables.
• These are marked in the shader with the modifyer uniform
• The red book says
  • They are shared between all stages of the shader.
  • They must be global variables (in the shaders)
  • They cannot be written to (in the shader)
  • see off1.vert for an example.
• Mapping between uniform variables and variables
  • GLint glGetUniformLocation( GLuint program, const GLchar *name);
    • Returns an integer representing a uniform variable.
      • or -1 if the variable does not exist.
      • Or if the name starts with gl_
      • Or some other conditions.
    • The iteger is valid until the shader program is changed.
    • Program is the program that was loaded.
    • name is the name of the vairable you are looking for.
    • They state that the variable location is not known until the program is linked.
  • void glUniform*
    • Many version of this one
    • copy a value from the cpu program to the gpu program.
  • void glGetUniform* gets the value of a uniform variable.