ir – 2 ∗ dot(surfaceNormal, eyeToSurfaceDir) ∗ surfaceNormal
      const reflect = eyeToSurfaceDir.map((incident, ndx) => {
        const normal = surfaceNormal[ndx];
        minusOneDot[ndx] = incident - dot * normal;
        return incident - 2 * dot * normal;
      });

      const ra = Math.atan2(...reflect) + Math.PI;
      {
        ctx.save();
        ctx.translate(-85, -85);
        ctx.scale(.25, .25);
        ctx.fillStyle = '#F00';
        ctx.strokeStyle = '#F00';
        const exToEdge = 