There’s a special piece of hardware between the vertex shader and the fragment shader: the Rasterizer

• it decides which pixels in the window are affected by the incoming geometric primitive
  • for our triangle, the rasterizer “generates” all of the fragments inside the triangle

Rasterizer as a linear interpolator

• computes the intermediate colors for all fragments inside the geometric primitive
• uses the values specified from the vertex shader as the values to interpolate
• assigns the interpolated value to the fragment shader’s varying variable