
      const ley = y +  eyeToSurfaceDir[1] * snScale;

      if (data.normals) {
        ctx.fillStyle = '#080';
        ctx.strokeStyle = '#080';
        diagram.arrow(ctx, x, y, snx, sny, false, true, 0.5);
        diagram.arrow(ctx, snx, sny, snx2, sny2, false, true, 0.5);
      }

      if (data.addedVectors) {
        ctx.fillStyle = '#FCC';
        ctx.strokeStyle = '#FCC';
        diagram.arrow(ctx, lex, ley, snx2, sny2, false, true, 0.3);
      }

      const minusOneDot = [];
      // eyeToSurfaceD