How to calculate normal for side face of Triangle?

[pluxy]

Hello,

I know how to set normal for quad as it is clear and easy to set the values something like below.
However it is hard for me to come up with right answer for side face of Triangle.

Not sure above is correct or not. but one thing I am sure is that if I set only normal in single direction, it become just black against the light.

However I’m getting weird result when I set normal in two direction with the same length.

Any idea to have proper normal for side face of Triangle?

Thanks,

[carsten_neumann]

The wiki page Calculating a Surface Normal describes how to do this.

[pluxy]

Thanks, but still I am getting same result