vec4 FUNCNAME(vec2 tc) {
// OpenGL's origin is bottom-left, but most graphics software assumes
// a top-left origin. Thus, for inputs that come from the user,
// we flip the y coordinate.
vec4 FUNCNAME(vec2 tc) {
// OpenGL's origin is bottom-left, but most graphics software assumes
// a top-left origin. Thus, for inputs that come from the user,
// we flip the y coordinate.