blender-archive/source/blender/draw/modes/shaders/paint_vert_frag.glsl

flat in vec4 finalColor;
out vec4 fragColor;

void main()
{
  vec2 centered = gl_PointCoord - vec2(0.5);
  float dist_squared = dot(centered, centered);
  const float rad_squared = 0.25;

  // round point with jaggy edges
  if (dist_squared > rad_squared) {
    discard;
  }

  fragColor = finalColor;
}