It's quick...
I would suggest that it's not actually doing shadow mapping as nothing is casting a shadow, also, you're not getting variation in brightness dependant on the slope incline/decline.
It's alright as a starting point, but certainly needs more work.
Look up cosine interpolation for when you've got a lightsource hitting it from different directions. It's a good way to find the inbetween points between points.
I would suggest that it's not actually doing shadow mapping as nothing is casting a shadow, also, you're not getting variation in brightness dependant on the slope incline/decline.
It's alright as a starting point, but certainly needs more work.
Look up cosine interpolation for when you've got a lightsource hitting it from different directions. It's a good way to find the inbetween points between points.