expression error f value not defined

over 8 years ago by Sam Worley

I'm on the first video around 5 min 30 sec, and the instructor appears to type in f*-1 as an expression in the unit x vector node to make a point move in the opposite direction. However, when I do this my node turns red, and the error under the balloon says unknown variable encountered:f. Please help, I know it's probably simple.